This Info file documents GNU troff version 1.12.

Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA  02111-1307  USA

Copyright (C) 1994, 1999 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled ``GNU General Public License'' is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled ``GNU General Public License'' may be included in a translation approved by the Free Software Foundation instead of in the original English.

This Info file documents groff version 1.13, the GNU implementation of the troff typesetting system.

This is an in-progress document; contributions, comments, or contributions are welcome.  Send them to bug-groff@gnu.org.

GNU GENERAL PUBLIC LICENSE
**************************

Version 2, June 1991

     Copyright © 1989, 1991 Free Software Foundation, Inc.
     59 Temple Place, Suite 330, Boston, MA 02111, USA

     Everyone is permitted to copy and distribute verbatim copies of this
     license document, but changing it is not allowed.

Preamble
========

The licenses for most software are designed to take away your freedom to share and change it.  By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software -- to make sure the software is free for all its users.  This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.)  You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights.  These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software.  If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary.  To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

 0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License.  The ``Program'', below, refers to any such program or work, and a ``work based on the Program'' means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term ``modification''.)  Each licensee is addressed as ``you''.

     Activities other than copying, distribution and modification are not covered by this License; they are outside its scope.  The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program).  Whether that is true depends on what the Program does.

 1. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

     You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

 2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:

      a. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

      b. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.

      c. If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License.  (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

     These requirements apply to the modified work as a whole.  If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works.  But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

     Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

     In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

 3. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:

      a. Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

      b. Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

      c. Accompany it with the information you received as to the offer to distribute corresponding source code.  (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

     The source code for a work means the preferred form of the work for making modifications to it.  For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable.  However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

     If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

 4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License.  Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License.  However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

 5. You are not required to accept this License, since you have not signed it.  However, nothing else grants you permission to modify or distribute the Program or its derivative works.  These actions are prohibited by law if you do not accept this License.  Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

 6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions.  You may not impose any further restrictions on the recipients' exercise of the rights granted herein.  You are not responsible for enforcing compliance by third parties to this License.

 7. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License.  If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all.  For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

     If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

     It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices.  Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

     This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

 8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded.  In such case, this License incorporates the limitation as if written in the body of this License.

 9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time.  Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

     Each version is given a distinguishing version number.  If the Program specifies a version number of this License which applies to it and ``any later version'', you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation.  If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

 10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission.  For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this.  Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.

     NO WARRANTY

 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs
=============================================

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program.  It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the ``copyright'' line and a pointer to where the full notice is found.

     ONE LINE TO GIVE THE PROGRAM'S NAME AND AN IDEA OF WHAT IT DOES.
     Copyright (C) 19YY NAME OF AUTHOR

     This program is free software; you can redistribute it and/or modify it
     under the terms of the GNU General Public License as published by the
     Free Software Foundation; either version 2 of the License, or (at your
     option) any later version.

     This program is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License along
     with this program; if not, write to the Free Software Foundation, Inc.,
     59 Temple Place, Suite 330, Boston, MA 02111, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

     Gnomovision version 69, Copyright (C) 19YY NAME OF AUTHOR
     Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type
     `show w'.  This is free software, and you are welcome to redistribute it
     under certain conditions; type `show c' for details.

The hypothetical commands show w and show c should show the appropriate parts of the General Public License.  Of course, the commands you use may be called something other than show w and show c; they could even be mouse-clicks or menu items---whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a ``copyright disclaimer'' for the program, if necessary.  Here is a sample; alter the names:

     Yoyodyne, Inc., hereby disclaims all copyright
     interest in the program `Gnomovision'
     (which makes passes at compilers) written
     by James Hacker.

     SIGNATURE OF TY COON, 1 April 1989
     Ty Coon, President of Vice

This General Public License does not permit incorporating your program into proprietary programs.  If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library.  If this is what you want to do, use the GNU Library General Public License instead of this License.

Introduction
************

GNU troff (or groff) is a system for typesetting documents.  troff is very flexible and has been in existence (and use) for about 3 decades.  It is quite widespread and firmly entrenched in the UNIX community.

What Is groff?
==============

groff is of an older generation of document preparation systems, which operate more like compilers than the more recent interactive WYSIWYG  (What You See Is What You Get) systems.  groff and its contemporary counterpart, TeX, both work using a batch paradigm: The input (or source) files are normal text files with embedded formatting commands.  These files can then be processed by groff to produce a typeset document on a variety of devices.

Likewise, groff should not be confused with a word processor, since that term connotes an integrated system which includes an editor and a text formatter.  Also, many word processors follow the WYSIWYG paradigm which was discussed earlier.

Although WYSIWYG systems may be easier to use, they have a number of disadvantages compared to troff:

  * They must be used on a bitmapped display to do any operations on your document.

  * Most of the WYSIWYG systems are either non-free or are not very portable.

  * troff is firmly entrenched in all UNIX systems.

  * It is difficult to have a wide range of capabilities available within the confines of a GUI/window system.

  * It is more difficult to make global changes to a document.

     ``GUIs normally make it simple to accomplish simple actions and impossible to accomplish complex actions.''  --Doug Gwyn (22/Jun/91 in comp.unix.wizards)

History
=======

troff can trace its origins back to a formatting program called runoff which ran on MIT's CTSS system.  This name came from the common phrase of the time ``I'll run off a document.''

The first version of UNIX was developed on a PDP-7 which was sitting around Bell Labs.  In 1971 the developers wanted to get a PDP-11 for further work on the operating system.  In order to justify the cost for this system, they proposed that they would implement a document formatting system for the AT&T patents division.  This first formatting program was a reimplementation of runoff.  In accordance with UNIX's penchant for abreviations, it was named roff (an abreviation of runoff).

When they needed a more flexible language, a new version of roff called nroff (Newer roff) was written.  It had a much more complicated syntax, but provided the basis for all future versions. When they got a Graphic Systems CAT Phototypesetter, J. F. Ossanna wrote a version of nroff which would drive it.  It was dubbed troff for typesetter roff, although many people have speculated that it actually means Times roff because of troff's use of the Times font family by default.  As such, the name troff is pronounced t-roff rather than trough.

With troff came nroff (they were actually the same program except for some #ifdefs), which was for producing output for line printers and ascii terminals.  It understood everything troff did, and ignored the commands which were not aplicable (i.e. font changes).

Since there are several things which cannot be done easily in troff, work on several preprocessors began.  These programs would transform certain parts of a document into troff, which made a very natural use of pipes in UNIX.

The eqn preprocessor allowed mathematical formulæ to be specified in a much simpler and more intuitive manner.  tbl is a preprocessor for formatting tables.  The refer preprocessor (and the similar program, bib) processes citations in a document according to a bibliographic database.

Unfortunately, Ossanna's troff was written in PDP-11 assembly language and produced output specifically for the CAT phototypesetter. He rewrote it in C, although it was now 7000 lines of uncommented code and still dependent on the CAT.  As the CAT became less common, and was no longer supported by the manufacturer, the need to make it support other devices became a priority.  However, before this could be done, he was killed in an auto accident.

So, Brian Kernighan took on the task of rewriting troff.  The newly rewritten version produced a device independent code which was very easy for postprocessors to read and translate to the appropriate printer codes.  Also, this new version of troff (called ditroff) had several extentions, which included drawing functions.

Due to the additional abilities of the new version of troff, several new preprocessors appeared.  The pic preprocessor provides a wide range of drawing functions.  Likewise the ideal preprocessor did the same, although via a much different paradigm.  The grap preprocessor took specifications for graphs, but, unlike other preprocessors, produced pic code.

James Clark began work on a GNU implementation of ditroff in early 1989.  The first version, groff 0.3.1, was released June 1990.  groff included

  * A replacement for ditroff with many extentions.

  * The soelim, pic, tbl, and eqn preprocessors.

  * Postprocessors for ascii devices, PostScript, TeX DVI, and X windows.  GNU troff also eliminated the need for a separate nroff program with a postprocessor which would produce ascii output.

  * A version of the -me macros and an implementation of the -man macros.

Also, a front-end was included which could construct the, sometimes painfully long, pipelines required for all the post- and preprocessors.

Development of GNU troff progressed rapidly, and saw the additions of a replacement for refer, an implementation of the -ms and -mm macros, and a program to deduce how to format a document (grog).

It was declared a stable (i.e. non beta) package with the release of version 1.04 around November 1991.

groff Capabilities
==================

So what exactly is groff capable of doing?  groff provides a wide range of low-level text formatting operations.  Using these, you can perform a wide range of formatting tasks, such as footnotes, table of contents, multiple columns, etc.

  * Text filling, adjusting, and centering

  * Hyphenation

  * Page control

  * Font and character size control

  * Vertical spacing (i.e. double spacing)

  * Line length and indenting

  * Macros, strings, diversions, and traps

  * Number registers

  * Tabs, leaders, and fields

  * Input and output conventions and character translation

  * Overstrike, bracket, line drawing, and zero-width functions

  * Local horizontal and vertical motions and the width function

  * Three-part titles

  * Output line numbering

  * Conditional acceptance of input

  * Environment switching

  * Insertions from the standard input

  * Input/output file switching

  * Output and error messages

Macro Packages
==============

Since groff provides such low level facilities, it can be quite difficult to use by itself.  However, groff provides a macro facility which allows you to specify how certain routine operations (e.g. starting paragraphs, printing headers and footers, etc.) should be done.  These macros can be collected together into a macro package.  There are a number of macro packages available; the most common (and the ones described in this manual) are -man, -me, -ms, and -mm.

Preprocessors
=============

Although groff provides most functions needed to format a document, some operations would be unwieldy (i.e. drawing pictures). Therefore, programs called preprocessors were written which understand their own language and produce the necessary groff operations.  These preprocessors are able to differentiate their own input from the rest of the document via markers.

To use a preprocessor, UNIX pipes are used to feed the output from the preprocessor into groff.  Any number of preprocessors may be used on a given document; in this case, the preprocessors are linked together into one pipeline.  However, in groff, the user does not need to construct the pipe, but only tell groff what preprocessors to use.

groff currently has preprocessors for producing tables (tbl), typesetting equations (eqn), drawing pictures (pic), and for processing bibliographies (refer).  An associated program which is useful when dealing with preprocessors is soelim.

There are other preprocessors in existence, but there are, unfortunately, no free implementations available.  They are for drawing pictures (ideal and gremlin), for drawing graphs (grap), and chemical structures (chem).

Postprocessors
==============

groff actually produces device independent code which may be fed into a postprocessor which will produce output for a particular device. Currently, groff has postprocessors for PostScript, ascii terminals, X windows (for previewing), TeX DVI format, and HTML.

Credits
=======

Large portions of this manual were taken from existing documents, most notably, the manual pages for the groff package by James Clark, and Eric Allman's papers on the -me macro package.

Invoking groff
**************

This section focuses on how to invoke the groff front end.  This front end takes care of the details of constructing the pipeline among the preprocessors, gtroff and the postprocessor.

It has become a tradition that GNU programs get the prefix g to distinguish it from its original counterparts provided by the host (see Environment, for more details).  Thus, for example, geqn is GNU eqn.  On operating systems like Linux or the Hurd, which don't contain proprietary software, this prefix is omitted since GNU troff is the only used incarnation of troff.  Exception: groff is never replaced by `roff'.

Options
=======

groff is a front-end to the groff document formatting system. Normally it runs the gtroff program and a postprocessor appropriate for the selected device.  The default device is ps. It can optionally preprocess with any of gpic, geqn, gtbl, grefer, or gsoelim.

This section only documents options to the groff front end.  Many of the arguments to groff are passed on to gtroff, therefore those are also included.  Arguments to pre- or postprocessors can be found in Invoking gpic, Invoking geqn, Invoking gtbl, Invoking grefer, Invoking gsoelim, Invoking grotty, Invoking grops, Invoking grohtml, Invoking grodvi, and Invoking gxditview

The command line format for groff is:

     groff [ -abehilpstvzCENRSVXZ ] [ -FDIR ] [ -mNAME ]
           [ -TDEF ] [ -fFAM ] [ -wNAME ] [ -WNAME ]
           [ -MDIR ] [ -dCS ] [ -rCN ] [ -nNUM ]
           [ -oLIST ] [ -PARG ] [ -LARG ]
           [ FILES... ]

The command line format for gtroff is as follows.  As you can see, many of the options to groff are actually passed on to gtroff.

     gtroff [ -abivzCER ] [ -wNAME ] [ -WNAME ] [ -dCS ]
            [ -fFAM ] [ -mNAME ] [ -nNUM ]
            [ -oLIST ] [ -rCN ] [ -TNAME ]
            [ -FDIR ] [ -MDIR ] [ FILES... ]

Options without an argument can be grouped behind a single -.  A filename of - denotes the standard input.

The grog command can be used to guess the correct groff command to use to format a file.

-h
     Print a help message.

-e
     Preprocess with geqn.

-t
     Preprocess with gtbl.

-p
     Preprocess with gpic.

-s
     Preprocess with gsoelim.

-R
     Preprocess with grefer.  No mechanism is provided for passing arguments to grefer because most grefer options have equivalent commands which can be included in the file.  See grefer, for more details.

     Note that gtroff also accepts a -R option, which is not accessible via groff.  This option prevents the loading of the troffrc file.

-v
     Make programs run by groff print out their version number.

-V
     Print the pipeline on stdout instead of executing it.

-z
     Suppress output from gtroff.  Only error messages will be printed.

-Z
     Do not postprocess the output of gtroff.  Normally groff will automatically run the appropriate postprocessor.

-PARG
     Pass ARG to the postprocessor.  Each argument should be passed with a separate -P option. Note that groff does not prepend - to ARG before passing it to the postprocessor.

-l
     Send the output to a printer.  The command used for this is specified by the print command in the device description file.

-LARG
     Pass ARG to the spooler.  Each argument should be passed with a separate -L option.  Note that groff does not prepend a - to ARG before passing it to the postprocessor.

-TDEV
     Prepare output for device DEV.  The default device is ps. The following are the output devices currently available:

     ps
          For PostScript printers and previewers.

     dvi
          For TeX dvi format.

     X75
          For a 75 dpi X11 previewer.

     X100
          For a 100dpi X11 previewer.

     ascii
          For typewriter-like devices.

     latin1
          For typewriter-like devices using the ISO Latin-1 character set.

     lj4
          For an HP LaserJet4-compatible (or other PCL5-compatible) printer.

     html
          To produce HTML output.

     The postprocessor to be used for a device is specified by the postpro command in the device description file.  (see Font Files, for more info.)  This can be overridden with the -X option.

-X
     Preview with gxditview instead of using the usual postprocessor. This is unlikely to produce good results except with -Tps.

-N
     Don't allow newlines with eqn delimiters.  This is the same as the -N option in geqn.

-S
     Safer mode.  Pass the -S option to gpic and use the -msafer macros with gtroff.

-a
     Generate an ASCII approximation of the typeset output.

-b
     Print a backtrace with each warning or error message.  This backtrace should help track down the cause of the error.  The line numbers given in the backtrace may not always be correct: troff's idea of line numbers gets confused by as or am requests.

-i
     Read the standard input after all the named input files have been processed.

-wNAME
     Enable warning NAME.  Available warnings are described in Debugging.  Multiple -w options are allowed.

-WNAME
     Inhibit warning NAME.  Multiple -W options are allowed.

-E
     Inhibit all error messages.

-C
     Enable compatibility mode.

-dCS
-dNAME=s
     Define C or NAME to be a string S; C must be a one-letter NAME.

-fFAM
     Use FAM as the default font family.

-mNAME
     Read in the file tmac.NAME.  Normally this will be searched for in groff's lib directory.

-nNUM
     Number the first page NUM.

-oLIST
     Output only pages in LIST, which is a comma-separated list of page ranges; N means print page N, M-N means print every page between M and N, -N means print every page up to N, N- means print every page from N.  troff will exit after printing the last page in the list.

-rCN
-rNAME=N
     Set number register C or NAME to N; C must be a one-letter NAME; N can be any troff numeric expression.

-FDIR
     Search DIR for subdirectories devNAME (NAME is the name of the device) for the DESC file and font files before the normal directory.

-MDIR
     Search directory DIR for macro files before the normal directory.

Environment
===========

There are also several environment variables which can modify groff's behavior.

GROFF_COMMAND_PREFIX
     If this is set to X, then groff will run Xtroff instead of gtroff.  This also applies to tbl, pic, eqn, refer, and soelim.  It does not apply to grops, grodvi, grotty, grohtml, grolj4, and gxditview.

GROFF_TMAC_PATH
     A colon separated list of directories in which to search for macro files.

GROFF_TYPESETTER
     Default device.

GROFF_FONT_PATH
     A colon separated list of directories in which to search for the devNAME directory.

PATH
     The search path for commands executed by groff.

GROFF_TMPDIR
     The directory in which temporary files will be created.  If this is not set and TMPDIR is set, temporary files will be created in that directory.  Otherwise temporary files will be created in /tmp. The grops and grefer commands can create temporary files.

Invocation Examples
===================

This section will list several common uses of groff and the command line which will accomplish it.

     groff file
     groff -X -me file
     groff -mm -rD1 -z file
     groff -tps -me file | lpr -Plw2
     ... any more?? ...

grog
----

grog reads files and guesses which of the groff preprocessors and/or macro packages are are required for formatting them, and prints the groff command including those options on the standard output.  The options generated are one of -e, -man, -me, -mm, -ms, -p, -s, and -t.

A filename of - is taken to refer to the standard input.  If no files are specified the standard input will be read.  Any specified options will be included in the printed command.  No space is allowed between options and their arguments.  For example,

     grog -Tdvi paper.ms

will guess the approriate command to print paper.ms and then run it after adding the -Tdvi option.

Tutorial for Macro Users
************************

Most users tend to use a macro package to format their papers.  This means that the whole breadth of groff is not neccessary for most people.  This chapter covers the material needed to efficiently use a macro package.

Basics
======

This section covers some of the basic concepts you will need to understand to use a macro package. (This section is derived from Writing Papers with nroff using -me by Eric P. Allman) References are made throughout to more detailed information, if desired.

groff reads an input file prepared by the user and outputs a formatted paper suitable for publication or framing.  The input consists of text, or words to be printed, and embedded commands (requests and escapes), which tell groff how to format the printed copy.  For more detail on this see Embedded Commands.

The word argument is used in this manual to mean a word or number which appears on the same line as a request which modifies the meaning of that request.  For example, the request

     .sp

spaces one line, but

     .sp 4

spaces four lines.  The number 4 is an argument to the sp request which says to space four lines instead of one.  Arguments are separated from the request and from each other by spaces.  More details on this can be found in Request Arguments.

The primary function of groff is to collect words from input lines, fill output lines with those words, justify the right hand margin by inserting extra spaces in the line, and output the result.  For example, the input:

     Now is the time
     for all good men
     to come to the aid
     of their party.
     Four score and seven
     years ago,...

will be read, packed onto output lines, and justified to produce:

     Now is the time for all good men to come to the aid of their party. Four score and seven years ago,...

Sometimes you may want to start a new output line even though the line you are on is not yet full; for example, at the end of a paragraph.  To do this you can cause a break, which starts a new output line. Some requests cause a break automatically, as do blank input lines and input lines beginning with a space.

Not all input lines are text to be formatted.  Some of the input lines are requests which describe how to format the text.  Requests always have a period or an apostrophe (') as the first character of the input line.

The text formatter also does more complex things, such as automatically numbering pages, skipping over page boundaries putting footnotes in the correct place, and so forth.

Here a few hints for preparing text for input to groff.  First, keep the input lines short.  Short input lines are easier to edit, and groff will pack words onto longer lines for you anyhow.  In keeping with this, it is helpful to begin a new line after every period, comma, or phrase, since common corrections are to add or delete sentences or phrases.  Secondly, do not hyphenate words at the end of lines -- groff is smart enough to hyphenate words for you as needed, but is not smart enough to take hyphens out and join a word back together.  Also, words such as ``mother-in-law'' should not be broken over a line, since then you will get a space where not wanted, such as ``mother- in-law''.

Groff will double space output text automatically if you use the request .ls 2.  You can revert to single spaced mode by typing .ls 1.

A number of requests allow you to change the way the printed copy looks, sometimes called the layout of the output page.  Most of these requests adjust the placing of white space (blank lines or spaces).

The .bp request starts a new page.

The request .sp N leaves N lines of blank space. N can be omitted (meaning skip a single line) or can be of the form Ni (for N inches) or Nc (for N centimeters).  For example, the input:

     .sp 1.5i
     My thoughts on the subject
     .sp

leaves one and a half inches of space, followed by the line ``My thoughts on the subject'', followed by a single blank line.

Text lines can be centered by using the .ce request.  The line after .ce is centered (horizontally) on the page.  To center more than one line, use .ce N (where N is the number of lines to center), followed by the N lines.  If you want to center many lines but don't want to count them, type:

     .ce 1000
     lines to center
     .ce 0

The .ce 0 request tells groff to center zero more lines, in other words, stop centering.

All of these requests cause a break; that is, they always start a new line.  If you want to start a new line without performing any other action, use .br.

Common Features
===============

Groff provides very low level operations for formatting a document. There are many common routine operations which are done in all documents. These common operations are written into macros and collected into a macro package.

All macro packages provide certain common capabilities which fall into the following categories.

Paragraphs
----------

One of the most common and most used capability is starting a paragraph.  There are a number of different types of paragraphs, any of which can be initiated with macros supplied by the macro package.  Normally paragraphs start with a blank line and the first line indented, like the text in this manual.  There are also block style paragraphs, which omit the indentation:

     Some   men  look   at  constitutions   with  sanctimonious
     reverence, and deem them like the ark of the covenant, too
     sacred to be touched.

And there are also indented paragraphs which begin with a tag or label at the margin and the remaining text indented.

     one   This is  the first paragraph.  Notice  how the first
           line of  the resulting  paragraph lines up  with the
           other lines in the paragraph.
     longlabel
           This  paragraph   had  a  long   label.   The  first
           character of text on the first line will not line up
           with  the  text  on  second  and  subsequent  lines,
           although they will line up with each other.

A variation of this is a bulleted list....

Sections and Chapters
---------------------

Most macro packages supply some form of section headers. The simplest kind is simply the heading on a line by itself in bold type.  Others supply automatically numbered section heading or different heading styles at different levels. Some, more sophisticated, macro packages supply macros for starting chapters and appendicies.

Headers and Footers
-------------------

Every macro packages gives you some way to manipulate the headers and footers (or titles on each page.  Some packages will allow you to have different ones on the even and odd pages (for material printed in a book form). The titles are called three-part titles, that is, there is a left-justified part, a centered part, and a right-justified part. An automatically generated page number may be put in any of these fields with the % character.

Page Layout
-----------

Most macro packages let you specify top and bottom margins and other details about the appearance of the printed pages.

Displays
--------

Displays are sections of text to be set off from the body of the paper.  Major quotes, tables, and figures are types of displays, as are all the examples used in this document.

Major quotes are quotes which are several lines long, and hence are set in from the rest of the text without quote marks around them.

A list is an indented, single spaced, unfilled display.  Lists should be used when the material to be printed should not be filled and justified like normal text, such as columns of figures or the examples used in this paper.

A keep is a display of lines which are kept on a single page if possible.  An example of where you would use a keep might be a diagram.  Keeps differ from lists in that lists may be broken over a page boundary whereas keeps will not.

Floating keeps move relative to the text.  Hence, they are good for things which will be referred to by name, such as ``See figure 3''.  A floating keep will appear at the bottom of the current page if it will fit; otherwise, it will appear at the top of the next page.  Meanwhile, the surrounding text will `flow' around the keep, thus leaving now blank areas.

Footnotes and annotations
-------------------------

There are a number of requests to save text for later printing.  Footnotes are printed at the bottom of the current page.  Delayed text is intended to be a variant form of foot- note; the text is printed only when explicitly called for, such as at the end of each chapter.

Delayed text is very similar to a footnote except that it is printed when called for explicitly.  This allows a list of references to appear (for example) at the end of each chapter, as is the convention in some disciplines.

Most macro packages which supply this functionality also supply a means of automatically numbering either type of annotation.

Table of Contents
-----------------

Tables of contents are a type of delayed text having a tag (usually the page number) attached to each entry after a row of dots.  The table accumulates throughought the paper until printed, usually after the paper has ended.  Many macro packages will provide the abilitly to have several tables of contents (i.e. one standard one, one for tables, &c.)

Indexes
-------

While some macro packages will use the term index, none actually provide that functionality.  The facilities they call indexes are actually more appropriate for tables of contents.

Paper formats
-------------

Some macro packages provide stock formats for various kinds of documents.  Many of them provide a common format for the title and opening pages of a technical paper.  The -mm macros in particular provide formats for letters and memorandums.

Multiple Columns
----------------

Some macro packages (except -man) provide the ability to have two or more columns on a page.

Font and Size changes
---------------------

The builtin font and size functions are not always intuitive, so all macro packages provide macros to make these operations simpler.

Predefined Strings
------------------

Most macro packages provide various predefined strings for a variety of uses, examples are sub- and super-scripts, printable dates, quotes and various special characters.

Preprocessor Support
--------------------

All macro packages provide support for the various preprocessors.

Configuration and Customization
-------------------------------

Some macro packages provide means of customizing many of details of how the package behaves.  This ranges from setting the default type size to changing the appearance of section headers.

-man
****

-ms
***

-me
***

-mm
***

Programming Tutorial
********************

This chapter covers all of the facilities of groff. If you are intending to use a macro package, you probably do not want to read this chapter.

Text
====

groff input files contain text with control commands interspersed throughout.  But, even without control codes, groff will still do several things with your text: filling and adjusting, adding additional space after sentences, hyphenating and inserting implicit line breaks.

Filling and Adjusting
---------------------

When troff reads in text it collects words from input and fits as many of them together on one output line as it can.  This is known as filling.

Once troff has a filled line it will try to adjust it. which means it will widen the spacing between words until the text reaches the right margin (in the default adjustment mode). Extra spaces between words are preserved, but spaces at the end of lines are ignored. Spaces at the front of a line will cause a break (breaks will be explained in Implicit Line Breaks)

See Manipulating Filling and Adjusting

Hyphenation
-----------

Since the odds of finding a set of words, for every output line, which will fit nicely on a line without inserting excessive amounts of space between words is not great, troff will hyphenate words so that lines can be justified without there being too much space between words. It uses an internal hyphenation algorithm, to indicate which words can be hyphenated and how to do so. When a word is hyphenated the first part of the word will be added to the current filled line being output (with an attached hyphen), and the other portion will be added to the next line to be filled.

See Manipulating Hyphenation

Sentences
---------

Although it is often debated, some typesetting rules say there should be different amounts of space after various puctuation marks. For example, a period at the end of a sentence should have twice as much space following it as would a comma or a period as part of an abbreviation.

Troff does this by flagging certain characters (normally !,  ? and .) as end of sentence characters. When troff encounters one of these characters at the end of a line it will append two sentence spaces in the formatted output. (thus, one of the conventions mentioned in Input Conventions).

Tab Stops
---------

Groff translates tabs in the input into movements to the next tab stop.  These tab stops are initially located every half inch across the page. Using this you can make simple tables.  However, this can often be deceptive as the appearance (and width) of your text on a terminal and the results from groff can vary greatly.

Also, a possible sticking point is that lines beginning with tab characters will still be filled, again producing unexpected results. For example, the following input

     	1	2	3
     		4	5

will produce

     	1	2	3		4	5

See Tabs and Fields

Implicit Line Breaks
--------------------

An important concept in troff is the break.  When a break occurs, troff will output the partially filled line (unadjusted), and resume collecting and filling text on the next output line.

There are several ways to cause a break in troff. A blank line will not only cause a break, but it will also cause a one line vertical space (effectively a blank line) to be output.

A line which begins with a space will cause a break and the space will be output at the beginning of the next line. Note that this space isn't adjusted, even in fill mode.

The end of file will also cause a break (otherwise the last line of your document may vanish!)

Certain requests also cause breaks, implicitly or explicity. This will be discussed later.

See Manipulating Filling and Adjusting

Input Conventions
=================

Since groff does filling automatically, it is traditional in groff not to try and type things in as nicely formatted paragraphs.  These are some conventions commonly used when typing groff text:

  * Break lines after punctuation, particularily at the ends of sentences, and in other logical places.  Keep separate phrases on lines by themselves, as entire phrases are often added or deleted when editing.

  * Try to keep lines less than 40-60 characters, to allow space for inserting more text.

  * Do not try to do any formatting in a WYSIWYG manner (i.e. don't try and use spaces to get proper indentation).

Measurements
============

Troff (like any other programs) requires numeric parameters to specify various measurements.  Most numeric parameters (those that specify vertical or horizontal motion or a type size) may have a measurement unit attached. These units are specified as a single character which immediately follows the number or expression. Each of these units are understood, by troff, to be a multiple of its basic unit.  So, whenever a different measurement unit is specified troff converts this into its basic units. This basic unit, represented by a u is a device dependent measurement which is quite small, ranging from 1/75th to 1/72000th of an inch.

Some of the measurement units are compleatly independent of any of the current settings (e.g. type size) of groff.

i
     Inches.  An antiquated measurement unit still in use in certain backwards countries.

c
     Centimeters.

p
     Points.  This is a typesetter's measurement used for measure type size. It is 72 points to an inch.

P
     Pica.  Another typesetting measurement.  6 Picas to an inch.

s

z

The other measurements understood by troff are dependent on settings currently in effect in troff.  These are very useful for specifying measurements which should look proper with any size of text.

m
     Ems.  This unit is equal to the current font size in points. So called because it is approximately the width of the letter m in the current font.

n
     Ens.  This is half of an em.

v
     Vertical space.  This is equivalent to the current line spacing. See Sizes, for more information about this.

M
     100ths of an em.

See Fractional Type Sizes

Default Units
-------------

Many requests take a default unit.  While this can be helpful at times, it can cause strange errors in some expressions. For example, the line  length  request  expects  em's. Here are several attempts to get 3.5 inches and the results:

     3.5i      =>   3.5i
     7/2       =>   0i
     7/2i      =>   0i
     7i/2      =>   .1i
     7i/2u     =>   3.5i

As you can see, the safest way to specify measurements is to always attach a scaling indicator.

Expressions
===========

Troff has most of operators common to other languages:

  * Arithmetic: +, -, /, *, %

  * Comparison: <, >, >=, <=, =, ==  (the last two are the same)

  * Logical: &, :

  * Unary operators: -, +, ! (if/while only??)

  * Maximum and minimum: >?, <?

  * Scaling: (C;E) Evaluate E using C as the default scaling indicator. If C is missing, ignore scaling indicators in the evaluation of E.

Parenthesis may be used as in any other language. However, in groff they are necessary to ensure order of evaluation. Groff has no operator precedence, expressions are evaluated left to right. This means that 3+5*4 is evaluated as if it were parenthesized like (3+5)*4, not as 3+(5*4), like you may expect.

For many requests which cause a motion on the page, the unary operators work differently. The + and - operators indicate a motion relative to the current position (down or up, respectively).  The | operator indicates an absolute position on the page or input line. (????) + and - are also treated differently by nr (?)

Due to the way arguments are parsed, spaces are not allowed in expressions, unless the entire expression is surrounded by parenthesis.

See Request Arguments see Conditionals and Loops

Identifiers
===========

Like any other language troff, has rules for properly formed identifiers. In troff an identifier can be made up of most any printable character. The only exception is characters which are interpreted by troff (backslash, square bracket and ?).  So, for example, any of the following are valid.

     br
     PP
     (l
     end-list
     @_

You can test whether an identifier is valid in groff with the \A escape.  It expands to 1 or 0 according whether its argument (given in quotes) is or is not acceptable as the name of a string, macro, diversion, number register, environment or font. It will return 0 if no argument is given. This is useful if you want to lookup user input in some sort of associative table.

Identifiers in groff can be any length, but, in some contexts, groff needs to told where identifiers end and text begins (and in different ways depending on their length)

  * Single character

  * Two characters Must be prefixed with ( in some situations.

  * Arbitrary length (groff only) Must be bracketed with [, ] in some situations. Any length identifier can be put in brackets.

Unlike many other programming languages, undefined identifiers are silently ignored or expanded to nothing.

See Interpolating Registers see Strings

Embedded Commands
=================

With most documents you need more funtionality beyond filling, adjusting and implicit line breaking. In order to gain further functionality, groff allows commands to be embeded into your text, in two ways.

The first is a request which takes up an entire line, and does some large scale operation (e.g. break lines, start new pages).

The other is an escape which can be embedded anywhere in your text, or even as an argument to a request. (Not always?) Escapes generally do more minor operations like sub- and super- scripts, print a symbol, &c.

Requests
--------

A request line begins with a control character, which is either a single quote (') or a period (.). These can be changed see Character Translations, for details. After this there may be optional tabs or spaces followed by an identifier which is the name of the request. This may be followed by any number of space separated arguments.

If you want to begin a line with a control character without it being interpreted, precede it with a \&.  This represents a zero width space, which means it will not affect you output.

In most cases you will use the period as a control character. Several requests will cause a break, using the single quote control character will prevent this.

Request Arguments
.................

Argument to requests (and macros) are processed much like the shell: The line is split into arguments according to spaces. An argument which is intended to contain spaces can either be enclosed in quotes (single or double), or have the spaces escaped with backslashes.

So, for example:

     .uh The Mouse Problem
     .uh "The Mouse Problem"
     .uh The\ Mouse\ Problem

The first line is the .uh macro being called with 3 arguments, The, Mouse, and Problem. The latter two have the same effect or calling the .uh macro with one argument The Mouse Problem.

Note, however, that the .ds request works differently.

See Strings

Macros
------

Troff has a macro facility for defining a series of lines which can be invoked by name. They are called in the same manner as requests and arguments may be passed in the same manner.

See Writing Macros see Request Arguments

Escapes
-------

Escapes may occur anywhere in the input to groff. They begin with a backslash and are followed by a single character which indicates the function to be performed. If you want to have a backslash appear in your document, you should use the escape sequence \e.  Merely escaping the backslash with another backslash will work in some curcumstances.

Many escapes have no parameters, those that do, do so in one of two ways.  For escapes which require an identifier there must be a way for groff to tell where the identifier ends and the text begins. It assumes that the next single character is the identifier, but if that character is an open parenthesis, it takes the next two characters as the identifier; and if the next character is an open bracket, all characters until a close bracket are taken as the identifier.  Note that in the second case there is no closing parenthesis.  For example:

     \fB
     \n(XX
     \*[TeX]

Other escapes may require several arguments and/or some special format.  In these cases the argument is enclosed in single quotes (not required??) and the enclosing text is decoded according to what that escape expects.

     \l'1.5i\(bu'

If you want to have a backslash appear in your output, you can use several escapes: \\, \e or \E. These are very similar, and only differ with respect to being used in macros or diversions (see Copy-in Mode, and Diversions, for more information)

See Identifiers

Comments
........

Probably one of the most (Unfortunately, this is a lie.  But hopefully future troff hackers will believe it :-)) common forms of escapes is the comment. They begin with the \" escape and end at the end of the input line.

This may sound simple, but it can be tricky to keep the comments from interfering with the apperarance of your final outupt.

If the escape is to the right of some text or a request, that portion of the line will be ignored, but the space leading up to it will be noticed by groff.  This only affects the .ds request (any others?).

One possibly irritating idiosyncracy is that you mustn't use tabs to line up your comments. Tabs are not treated as white space between request and macro arguments.

If you have a comment on a line by itself, it will be treated as a blank line, because after eliminating the comment, that is all that remains.  So, it is common to start the line with .\" which will cause the line to be treated as an undefined request.

Another commenting scheme seen sometimes is three consecutive single quotes (''') at the begining of a line.  This works, but groff will give a warning about an undefined macro, which is harmless, but irritating.

Now to avoid all this groff has a new comment mechanism using the \# escape.  This escape works the same as \" except that the newline is also ignored.

For large blocks of text, the ig request may be useful. See Strings

Registers
=========

Registers are groff's numeric variables.  groff has a number of builtin registers, supplying anything from the date to details of formatting parameters.

See Identifiers

Setting Registers
-----------------

Registers are defined/set via the nr request or the \R escape, for example, the following two lines are equivalent:

     .nr a 1
     \R'a 1'

The rr request will remove the register specified by the argument.

The rnn request will rename a number register. The format is .rnn X Y, which will rename number register  X to Y.

Aliases can be created for a number register.  The format is .aln XX YY, which will create an alias XX for number register object named YY.  The new name and the old name will be exactly equivalent.  If YY is undefined, a warning of type reg will be generated, and the request will be ignored. See Debugging, for information about warnings.

Interpolating Registers
-----------------------

Numeric registers are interpolated via the \n escape.

     .nr as \na+\na
     \n(as

Auto-increment
--------------

Number registers can also be auto incremented/decremented.  You can specify the increment/decrement factor with third argument to the nr request.  The default value is 0.  For example:

     .nr a 0 1
     .nr xx 0 5
     \n+a, \n+a, \n+a, \n+a, \n+a
     .br
     \n+(xx, \n+(xx, \n+(xx, \n+(xx, \n+(xx

Produces:

     1, 2, 3, 4, 5
     5, 10, 15, 20, 25

If you want to change the increment factor without changing the value of a register, the following can be used.

     .nr a \na 10

Assigning Formats
-----------------

When a register is used in the text of an input file (as opposed to part of an expression) it is textually replaced (or interpolated) with a representation of that number. This output format can be changed to a variety of formats (numbers, roman numerals, etc) This is done using the af request. The first argument to af is the name of the number register to be changed, and the second argument is the output format. The following output formats are available:

1
     This is the default format, decimal numbers: 1, 2, 3, ...

001
     Decimal numbers with as many leading zeros as specified. So, 001 would result in 001, 002, 003, ...

I
     Upper-case roman numerals: 0, I, II, III, IV, ...

i
     Lower-case roman numerals: 0, i, ii, iii, iv, ...

A
     Upper-case letters: A, B, C, ..., Z, AA, AB, ...

a
     Lower-case letters: a, b, c, ..., z, aa, ab, ...

The following example will produce 10, X, j, 010.

     .nr a 10
     .af a 1           \" the default format
     \na,
     .af a I
     \na,
     .af a a
     \na,
     .af a 001
     \na

The \g escape returns the current format of the specified register.  For example, \ga after the following example would produce 001.

Builtin Registers
-----------------

The following are some builtin registers, which are not listed elsewhere in this manual.  Any registers which begin with a . are read-only.  A compleat listing of all builtin registers can be found in Register Index.

.H
     Horizontal resolution in basic units.

.V
     Vertical resolution in basic units.

dw
     Day of the week (1-7).

dy
     Day of the year (1-31).

mo
     Current month (1-12).

yr
     Last two digits of the current year (see you in 7 years :-)

.c
c.
     The current input line number.

ln
     The current output line number.

.x
     The  major  version  number.  For example, if the version number is 1.03 then .x will contain 1.

.y
     The minor version number.  For example, if the version number is 1.03 then .y will contain 03.

.g
     Always 1. Macros should use this to determine whether they are running under GNU troff.

.A
     If the current output device is ascii, this is set to 1, zero otherwise.

.P
     This register indicates whether the current page is actualy being printed, i.e. if the -o option is being used to only print selected pages. See Options, for more information.

Manipulating Filling and Adjusting
==================================

Several ways of causing breaks were given in Implicit Line Breaks. The br request will likewise cause a break. Several other requests will also cause breaks, implicitly. They are bp, ce, fi, fl, in, nf, sp and ti.

Initially, groff will fill and ajust text to both margins. Filling can be disabled via the nf request and re-enabled with the fi request. These implicitly disable and re-enable adjusting. Both of these will cause break in text currently being filled. The number register .u is equal to 1 in fill mode and 0 in no-fill mode.

Adjusting can be disabled with the ad request and re-enabled with the na request. The ad request takes a single argument to indicate how to adjust text. The current adjustment mode is available in the number register .j.

l
     Adjust text to the left margin.  This produces what is traditionally called ragged-right text.

r
     Adjust text to the right margin.

c
     Center filled text.

b
n
     Justify to both margins.  This is groff's default.

With no argument to ad, troff will adjust lines the same way it was the last time it was filling.  For example:

     text
     .ad r
     text
     .ad c
     text
     .na
     text
     .ad  \" back to centering
     text

The escape \p will cause a break and cause the remaining text to be adjusted.

The ss request allows you to change the minimum size of a space between filled words. This request takes it's units as one twelfth of the spacewidth parameter for the current font.  Initially both the word space size and the sentence space size are 12.

When two arguments are given to the ss request, the second argument gives the sentence space size. If the second argument is not given, the sentence space size will be the same as the word space size. The sentence space size is used in two circumstances: if the end of a sentence occurs at the end of a line in fill mode, then both an inter-word space and a sentence space will be added; if two spaces follow the end of a sentence in the middle of a line, then the second space will be a sentence space. Note that the behaviour of UNIX troff will be exactly that exhibited by GNU troff if a second argument is never given to the ss request. In GNU troff, as in UNIX troff, you should always follow a sentence with either a newline or two spaces.

The number registers .ss and .sss are the values of the parameters set by the first and second arguments of the ss request.

The ce request will center text. While the ad c request will also center text, it has the side effect of filling the text.  The .ce request will not fill the text it affects. This request causes a break.

With no arguments, ce will fill the next line of text. The single argument ce takes is a number indicating the number of lines to be centered.  With no argument centering is disabled.

A common idiom is to turn on centering for a large number of lines, and then turn off centering when you are done with the centered text. This is useful for any request which takes a number of lines as an argument.

     .ce 1000
     replace this
     with
     something
     more interesting
     ...
     .ce 0

The .ce number register contains the number of lines remaining to be centered, as set by the ce request.

A similar request is rj request which will justify unfilled text to the right margin.  Its arguments are identical to the ce request. The .rj number register is the number of lines to be right-justified as set by the rj request.

Manipulating Hyphenation
========================

As discussed in Hyphenation, groff will hyphenate words. There are a number of ways to modify the how hyphenation is done.

This hyphenation can be turned off with the nh request, and turned back on with the hy request.  However, troff's hyphenation facilities are far more flexible than this.  The hy request can be used to tell troff to restrict hypenation to certain cases.  The request takes a single numeric argument. The current hyphenation restrictions can be found in the number register .hy

1
     The default argument, which indicates to hyphenate without restrictions.

2
     Do not hyphenate the last word on a page or column.

4
     Do not hyphenate the last two characters of a word.

8
     Do not hyphenate the first two characters of a word.

The hlm request will set the maximum number of consecutive hyphenated lines to the value given as the first argument. If this number is negative, there is no maximum.  The default value is -1. This value is associated with the current environment.  Only lines output from an environment count towards the maximum associated with that environment. Hyphens resulting from \% are counted; explicit hyphens are not. The current setting of this is available in the .hlm request. Also the number of immediately preceding consecutive hyphenated lines are available in the number register .hlc.

The hw request allows you to specify how a specific word is to be hyphenated.  It takes only one argument which is the word with hyphens at the hyphenation points.  For example: .hw in-sa-lub-rious.

You can also tell troff how to hyphenate words on the fly with the use of the \% escape, also known as the hyphenation character.  Preceding a word with this character will prevent it from being hyphenated, putting it in a word will indicate to troff that the word may be hyphenated at that point.  Note that this mechanism will only affect one word, if you want to change the hyphenation of a word for the entire document, use the hw request.

The hc request allows you to change the hyphenation character. The character specified as an argument will then work the same as the \% escape, and, thus, no longer appear in the output.  Without an argument it will return the hyphenation character to \%.

To further customize hyphenation the hpf request will read in a file of hyphenation patterns. This file will be searched for in the same way that tmac.NAME is searched for when the -mNAME option is specified.

It should have the same format as the argument to the \patterns primitive in TeX; the letters appearing in this file are interpreted as hyphenation codes. A % character in the patterns file introduces a comment that continues to the end of the line.

The set of hyphenation patterns is associated with the current language set by the hla request.  The hpf request is usually invoked by the troffrc file.

.hcode C1 CODE1 C2 CODE2... Set the hyphenation code of character C1 to code1 and that of C2 to CODE2. A hyphenation code must be a single input character (not a special character) other than a digit or a space.  Initially each lower-case letter has a hyphenation code, which is itself, and each upper-case letter has a hyphenation code which is the lower case version of itself.

The hym request will set the hyphenation margin to the value given as the first argument: when the current adjustment mode is not b, the line will not be hyphenated if the line is no more than that amount short. The default hyphenation margin is 0.  The default scaling indicator for this request is m.  The hyphenation margin is associated with the current environment.  The current hyphenation margin is available in the .hym register.

The hys request set the hyphenation space to the value given as the first argument: when the current adjustment mode is b, don't hyphenate the line if the line can be justified by adding no more than that amount of extra space to each word space.  The default hyphenation space is 0.  The default scaling indicator for this request is m.  The hyphenation space is associated with the current environment.  The current hyphenation space is available in the .hys register.

The shc request will set the soft hyphen character to the argument given as an argument.  If the argument is omitted, the soft hyphen character will be set to the default \(hy. The soft hyphen character is the character which will be inserted when a word is hyphenated at a line break.  If the soft hyphen character does not exist in the font of the character immediately preceding a potential break point, then the line will not be broken at that point.  Neither definitions (specified with the char request) nor translations (specified with the tr request) are considered when finding the soft hyphen character.

The hla request will set the current hyphenation language to that given by the first argument.  Hyphenation exceptions specified with the hw request and hyphenation patterns specified with the hpf request are both associated with the current hyphenation language.  The hla request is usually invoked by the troffrc file.  The current hyphenation language is available in the number register .hla.

Manipulating Spacing
====================

The sp request will cause troff to space downwards the distance specified as the first argument.  With no argument it will advance 1 line. A negative argument will cause troff to move up the page the specified distance. If the argument is preceded by a | troff will move that distance from the top of the page.

Often you may want your output to be double or triple spaced. The ls request will cause troff to output N-1 blank lines after each line of text, where N is the argument given to the ls request.  With no argument troff will go back to single spacing.  The number register .L contains the current line spacing setting.

Sometimes, extra vertical spacing is only needed occasionaly, i.e. to allow space for a tall construct (like an equation). The \x escape will do this. The escape is given a numerical argument (like \x'3p'). If this number is positive extra vertical space will be inserted below the current line.  A negative number will add space above. If this escape is used multiple times on the same line, the maximum values are used. The .a number register contains the most recent extra vertical emph line space.

     ... example of inline equation ...

Spacing (via either sp or via blank lines) can be disabled with the ns request.  This will enable no-space mode. This mode will end when actual text is output or the rs request is encountered.  No-space mode will also prevent requests to advance to the next page unless they are accompanied by a page number (see Page Control, for more information.)

Tabs and Fields
===============

Tab stops are much like those on a typewriter: a tab character (or the \t escape) on input will cause horizontal motion to the next tab stop.

Tab stops can be changed with the ta request. This request takes a series of numbers as arguments which indicate where each tab stop is to be (overriding any previous settings). These can be specified absolutely, i.e. as the distance from the left margin. For example, the following wil set tab stops every one inch.

     .ta 1i 2i 3i 4i 5i 6i

Tab stops can also be specified relatively (using a leading +) which means that the specified tab stop will be set that distance from the previous tab stop.  For example the following is equivalent to the previous example.

     .ta 1i +1i +1i +1i +1i +1i

After the specified tab stops repeat values may be set for tabs beyond the last one specified.  This is most commonly used to specify tabs set at equal intervals.  The compleat syntax for setting tabs is ta N1 N2 ... NN T R1 R2 ... RN This will set tabs at positions N1, N2, ..., NN and then set tabs at NN+R1, NN+R2, ..., NN+RN and then at NN+RN+R1, NN+RN+R2, ..., NN+RN+RN, and so on.  For example the following is, yet again, the same as the previous examples.

     .ta T 1i

The material in each tab column may be justified to the right or left or centered in the column.  This is specified by appending an R, L or C to the number specifying that tab stop. The default justification is L.

     .ta 1i 2iC 2iR

The number register .tabs contains a string representation of the current tab settings suitable for use as an argument to the ta request.

Normally troff will fill the space to the next tab stop with spaces. In some cases you may wish to change this.  The tc request will do this.  With no argument troff will revert to using spaces.

Leaders
-------

Sometimes you may wish to use the tc request to fill a tab stop with a given character, but also, you want to use normal tab stops on the rest of the line.  For this groff provides an alternate tab mechanism, called leaders which will do just that. They are used exclusively to produce a repeated run of characters to the next tab stop.

You can declare what character will be repeated with the lc request.  If you do not give it an argument, the leaders will act the same as tabs.

The difference is that a leader is invoked by using the \a escape.

So for a table of contents you may want to have tab stops defined so that the section number is one tab stop, the title is the second with the remaining space being filled with a line of dots and then the page number slightly separated from the dots.

     .lc .
     .ta .5iR 5i +.25i
     1.1\tFoo\a\t12

Fields
------

Fields are a more general way of laying out tabular data. fc

Character Translations
======================

The control character (.) and the no-break control character (') can be changed with the cc and c2 requests, respectively. The single argument is the new character to be used, with no argument the normal control character is restored.

The eo request will compleatly disable the escape mechanism. The ec request can be used to change the escape character from the default \ to what is specified as an argument.

The tr request will translate characters.

trnt This is the same as the tr request except that the translations do not apply to text that is transparently throughput into a diversion with \!.  See Diversions, for more information. For example,

     .tr ab
     .di x
     \!.tm a
     .di
     .x

will print b; if trnt is used instead of tr it will print a.

Line Layout
===========

The following drawing shows the dimensions which troff uses for placing a line of output onto the page.  They are labeled with the request which manipulates that dimension.

                   | -->| in |<--                   |
                -->| po |<-----------ll------------>|
                   +----+----+----------------------+----+
                   |    :    :                      :    |
                   +----+----+----------------------+----+

These dimensions are:

po
     Page offset--This is the leftmost postition of text on the final output.  This can be adjusted with the po request, and the current setting can be found in the builtin number register .o Note, that this request does not cause a break, so changing the page offset in the middle of text being filled may not do what you expect.

in
     Indentation--This is the distance from the left margin where text will be printed.  This can be adjusted with the in request, and the current setting can be found in the builtin number register. .i This request causes a break.

     There is also the request ti which will cause one output line to be indented, after which the indentation returns to 0. This request causes a break. The number register .in is the indent that applies to the current output line.

ll
     Line length--This is the distance from the left margin to right margin.  This can be adjusted with the .ll request, and the current setting can be found in the builtin number register .l Note, as the figure implies, line length is not affected by the current indentation. The number register .ll is the line length that applies to the current output line.

     .in +.5i
     .ll -.5i
     A bunch of really boring text which should
     be indented from both margins.
     replace me with a better (and more) example!
     .in -.5i
     .ll +.5i

Page Layout
===========

Troff provides some very primitive operations for controlling page layout.

Troff lets you specify the page length via the pl request. This is the length of the physical output page. The current setting can be found in the builtin number register .p.  Note that this only specifies the size of the page, not the not the top and bottom margins. Those are not done by groff directly, see Traps, for further information on how to do this.

Troff provides several operations which help in setting up top and bottom titles (or headers and footers)

The tl request will print a title line, which consists of three parts: a left justified portion, a centered portion and a right justified portion.  The argument to tl is specified as 'LEFT'CENTER'RIGHT' The % character is replaced with the current page number.

The title line is printed using its own line length, which is specified with the lt request.  The current setting of this is available in the .lt number register.

The pn request will change the page number of the next page.  The only argument is the page number.

The current page number is stored in the number register %. The number register .pn contains the number of the next page: either the value set by a pn request, or the number of the current page plus 1.

The pc request will change the page number character (used by the tl request) to a different character.  With no argument, this mechanism is disabled.

See Traps

Page Control
============

To stop processing the current page, and move to the next page, you can invoke the bp request.  This request will also cause a break.  This request can also take an argument of what the next page should be numbered. The only difference between bp and pn is that pn does not cause a break or actually eject a page.

     .de newpage
     'bp
     'sp .5i
     .tl 'left top'center top'right top'
     'sp .3i
     ..

Often you may want to make sure that you have a certain amount of space before a new page occurs.  This is most useful to make sure that there is not a single orphan line left at the bottom of a page.  The ne request will ensure that there is a certain distance, specified by the first argument, before the next page is triggered (see Traps, for further information). The default unit for ne is v's and the default argument is 1v.

For example, to make sure that no fewer than 2 lines get orphaned, you can do the following before each paragraph.

     .ne 2
     .ti +5n
     text

The sv is similar to the ne request, it reserves the specified amount of vertical space.  If the desired amount of space exists before the next trap (bottom page boundary), the space will be output immediately.  If there is not enough space, it is stored for later output via the os request. The default argument is 1v and the default units are v's.

Fonts
=====

Groff gives you the ability to switch fonts at any point in your text.  There are two ways to do this, via the ft request and the \f escape.

Fonts are generaly specified as uppercase strings, which are usually 1 to 4 characters representing an abreviation of acronym of the font name.

The basic set of fonts are R, I, B, and BI.  These are Times Roman, Italic, Bold, and Bold Italic.  There is also at least one symbol font which contains various special symbols (greek, mathematics). These latter fonts cannot be used directly, but should be used via an escape.

Changing Fonts
--------------

You can change fonts with both the ft request. With no arguments it will switch to the previous font (also known as P).

     eggs, bacon,
     .ft B
     spam
     .ft
     and sausage.

The \f escape is useful for changing fonts in the middle of words

     eggs, bacon, \fBspam\fP and sausage.

Both of the above examples will produce the same output.

Sometimes when putting letters of different fonts, you need more or less space at such boundaries.  There are two escapes to help with this.

The \/ escape increases the width of the preceding character so that the spacing between that character and the following character will be correct if the following character is a roman character.  For example, if an italic f is immediately followed by a roman right parenthesis,  then in many fonts the top right portion of the f will overlap the top left of the right parenthesis. It is a good idea to use this escape sequence whenever an italic character is immediately followed by a roman character without any intervening space.

The \, escape modifies the spacing of the following character so that the spacing between that character and the preceding character will correct if the preceding character is a roman character. It is a good idea to use this escape sequence whenever a roman character is immediately followed by an italic character without any intervening space.

The ftr request will translate fonts, it is called as .ftr F G, which Translate font F to G. Whenever a font named F is referred to in \f escape sequence, or in the ft, UL, BD, CS, TKF, SPECIAL, FSPECIAL, FP, or STY requests, font G will be used.  If G is missing, or equal to F then font F will not be translated.

Font Families
-------------

Due to the variety of fonts available, groff has added the concept of font families.  Each of these families has four styles (R, I, B and BI),

The fonts are specified as the concatenation of the font family and style.  Specifying a font without the family part will cause groff to use that style of the current family. By default, groff uses the Times family.

This way, you can just use the basic four fonts and select a different font family on the command line.

You can also switch font families with the fam request The current font family is available in the number register .fam. This is a string-valued register.

     spam,
     .fam H
     spam,
     .ft B
     spam,
     .fam T
     spam,
     .ft AR
     baked beans,
     .ft R
     and spam.

Font Positions
--------------

For the sake of old phototypesetters and compatability with old versions of troff, groff has the concept of font positions, on which various fonts are mounted. The last one or two are reserved for the symbol font(s).

New fonts can be mounted with the fp request. These numeric positions can then be referred to with font changing commands. When groff starts it is using font number one.

     .fp 1 H
     .fp 2 HI
     .fp 3 HB
     wink, wink,
     .ft 2
     nudge, nudge,
     .ft
     .ft 3
     say no more!
     .ft

(note that after these font changes have taken place the original font is restored.)

The current font in use, as a font position. This can be useful to remember the current font, for later recall.

     .nr save-font \n(.f
     ... lots 'o text ...
     .ft \n[save-font]

The number of the next free font position is available in the number register .fp.  This is useful when mounting a new font, like so:

     .fp \n[.fp] NEATOFONT

Fonts not listed in the DESC file are automatically mounted on the next available font position when they are referenced. If a font is to be mountfed explicitly with the fp request on an unused font position, it should be mounted on the first unused font position, which can be found in the .fp register; although troff does not enforce this strictly, it will not allow a font to be mounted at a position whose number is much greater than that of any currently used position.

The fp request has an optional third argument. This argument gives the external name of the font, which is used for finding the font description file.  The second argument gives the internal name of the font which is used to refer to the font in troff after it has been mounted.  If there is no third argument then the internal name will be used as the external name.  This feature allows you to use fonts with long names in compatibility mode.

Using Symbols
-------------

Symbols can be inserted by using a special escape sequence. This escape is simply the escape character (a backslash) followed by an identifier.  The symbol identifiers have to be two or more characters, since single characters conflict with all the other escapes.  The identifier can be either preceded by a parenthesis if it is two character, or surrounded by square brackets. So, the symbol for pi can be produced either by \(*p or \[*p].

     area = \(*p\fIr\fP\u2\d

The escape \C'XXX' will typeset character named XXX.  Normally it is more convenient to use \[XXX]. But \C has the advantage that it is compatible with recent versions of ditroff and is available in compatibility mode.

The escape \N'N' will typeset the character with code N in the current font.  N can be any integer.  Most devices only have characters with codes between 0 and 255.  If the current font does not contain a character with that code, special fonts will not be searched.  The \N escape sequence can be conveniently used on conjunction with the char request:

     .char \[phone] \f(ZD\N'37'

The code of each character is given in the fourth column in the font description file after the charset command.  It is possible to include unnamed characters in the font description file by using a name of ---; the \N escape sequence is the only way to use these.

Each character has certain properties associated with it. These properties can be modified with the cflags request. The first argument is the the sum of the desired flags and the remaining arguments are the characters to have those properties.

1
     the character ends sentences (initially characters .?! have this property);

2
     lines can be broken before the character (initially no characters have this property);

4
     lines can be broken after the character (initially characters -\(hy\(em have this property);

8
     the character overlaps horizontally (initially characters \(ul\(rn\(ru have this property);

16
     the character overlaps vertically (initially character \(br has this property);

32
     an end of sentence character followed by any number of characters with this property will be treated as the end of a sentence if followed by a newline or two spaces; in other words the character is transparent for the purposes of end of sentence recognition; this is the same as having a zero space factor in TeX (initially characters "')]*\(dg\(rq have this property).

You can create new characters with the char request.  It is called as .char C STRING Define character C to be STRING. Every time character C needs to be printed, STRING will be processed in a temporary environment and the result will be wrapped up into a single object.  Compatibility mode will be turned off and the escape character will be set to \ while STRING is being processed.  Any emboldening, constant spacing or track kerning will be applied to this object rather than to individual characters in STRING.  A character defined by this request can be used just like a normal character provided by the output device. In particular other characters can be translated to it with the tr request; it can be made the leader character by the lc request; repeated patterns can be drawn with the character using the \l and \L escape sequences;  words containing the character can be hyphenated correctly, if the hcode request is used to give the character a hyphenation code. There is a special anti-recursion feature: use of character within the character's definition will be handled like normal characters not defined with char.

A character definition can be removed with the rchar request.  Its arguments are the characters to be removed.  This undoes the effect of a char request.

See Special Characters

Artificial Fonts
----------------

There are a number of requests for artificially creating fonts. These are largely vestigal remains from the days when output devices did not have a wide variety of fonts, and when nroff and troff were separate programs. These are no longer necessary in GNU Troff.

The ul request will print subsequent lines in italics on a device capable of it, or underline the text on an ascii output device. The single argument is the number of lines to be ``underlined,'' with no argument, the next line will be underlined.

The cu request is similar to ul ...

The uf request will set the underline font used by ul and cu.

The bd request artificially creates a bold font by printing each character twice, slightly offset. The first argument specifies the font to embolden, and the second is the number of basic units, minus one, by which the two characters will be offset.  If the second argument is missing, emboldening will be turned off.

Ligatures and Kerning
---------------------

lg .lg The current ligature mode.

What is kerning??

If the font description file contains pairwise kerning information, characters from that font will be kerned.  Kerning between two characters can be inhibited by placing a \& between them.

kern If n is non-zero or missing, enable pairwise kerning, otherwise disable it. .kern 1 if pairwise kerning is enabled, 0 otherwise.

.tkf f s1 n1 s2 n2 Enable track kerning for font f.  When the current font is f the width of every character will be increased by an amount between n1 and n2; when the current point size is less than or equal to s1 the width will be increased by n1; when it is greater than or equal to s2 the width will be increased by n2; when the point size is greater than or equal to s1 and less than or equal to s2 the increase in width is a linear function of the point size.

Sizes
=====

Groff uses two dimensions with each line of text, type size and vertical spacing.  The type size is the height from the text baseline to the top of the tallest character (decenders may drop below this baseline).  Vertical spacing is the amount of space groff allows for a line of text, normally, this is about 20% larger than the current type size.  Ratios smaller than this can result in hard-to-read text, larger that this, it will spread your text out more vertically (useful for term papers).  By default, troff uses 10 point type on 12 point spacing.

The difference between type size and vertical spacing is known, by typesetters, as leading.

Changing Type Sizes
-------------------

Using the ps request and the \s escape you can change the type size.  The vs request will change the vertical spacing. The default unit for the ps and vs requests are points. The number registers .s and .v contain the current type size and vertical spacing.

These requests take parameters in units of points.  You can specify sizes as an absolute size, or as a relative change from the current size.  The size 0 means go back to the previous size.  With no argument it will revert to the previous size.

     snap, snap,
     .ps +2
     grin, grin,
     .ps +2
     wink, wink, \s+2nudge, nudge,\s+8 say no more!
     .ps 10

The \s escape may be called in a variety of ways. Much like other escapes there must be a way to determine where the argument ends and the text begins. Any of the following forms are valid: \sN, \s+N, \s-N, \s(NN, \s+(NN, \s-(NN, \s[+NNN], \s[-NNN], \s+[NNN], \s-[NNN].

Some devices may only have certain permissible sizes, in which case groff will round to the nearest permissible size.

     ... .sz macro example?? ...

Fractional Type Sizes
---------------------

A scaled point is equal to 1/SIZESCALE points, where SIZESCALE is specified in the DESC file (1 by default.) There is a new scale indicator z which has the effect of multiplying by SIZESCALE.  Requests and escape sequences in troff interpret arguments that represent a pointsize as being in units of scaled points, but they evaluate each such argument using a default scale indicator of z.  Arguments treated in this way are the argument to the ps request, the third argument to the cs request, the second and fourth arguments to the tkf request, the argument to the \H escape sequence, and those variants of the \s escape sequence that take a numeric expression as their argument.

For example, suppose SIZESCALE is 1000; then a scaled point will be equivalent to a millipoint; the request .ps 10.25 is equivalent to .ps 10.25z and so sets the pointsize to 10250 scaled points, which is equal to 10.25 points.

The number register \n(.s returns the pointsize in points as decimal fraction.  There is also a new number register \n[.ps] that returns the pointsize in scaled points.

It would make no sense to use the z scale indicator in a numeric expression whose default scale indicator was neither u nor z, and so troff disallows this.  Similarily it would make no sense to use a scaling indicator other than z or u in a numeric expression whose default scale indicator was z, and so troff disallows this as well.

There is also new scale indicator s which multiplies by the number of units in a scaled point.  So, for example, \n[.ps]s is equal to 1m.  Be sure not to confuse the s and z scale indicators.

\s'+N' \s'-N' \s+'N' \s-'N' Set the point size to N scaled points; N is a numeric expression with a default scale indicator of z.

\n[.ps] The current pointsize in scaled points.

\n[.psr] The last-requested pointsize in scaled points.

\n[.sr] The last requested pointsize in points as a decimal fraction.  This is a string-valued register.

See Font Files

Strings
=======

Groff has string variables, which are entirely for user convenience (i.e. there are no builtin strings) They are defined via the ds request.

     .ds UX \s-1UNIX\s0\u\s-3tm\s0\d

The are interpolated, or expanded in-place, via the \* escape:

     The \*(UX Operating System

Will produce:

     The UNIXtm Operating System

If the string named by the \* does not exist, the escape will be replaced by nothing.

NOTE:  Unlike other requests the third argument takes up the entire line including trailing spaces.  This means that comments on a line with such a request can introduce unwanted space into a string.

     .ds UX \s-1UNIX\s0\u\s-3tm\s0\d \" trademark of you-know-who

Instead you should either put the comment on another line or have the comment escape adjacent with the end of the string.

     .ds UX \s-1UNIX\s0\u\s-3tm\s0\d\"  trademark of you-know-who

If you need leading space you can start the string with a double quote.  No trailing quote is needed, in fact any trailing quote is included in your string.

     .ds sign "           Yours in a white wine sauce,

You can also append onto a string with the as request. It works the same as the ds request except that it appends the second argument onto the string named by the first argument.

     .as sign " with shallots, onions and garlic,

Strings are not limited to a sigle line of text.  A string can span several lines by escaping the newlines with a backslash.  The resulting string will be stored without the newlines.

     .ds foo lots and lots \
     of text are on these \
     next several lines

rn

rm

als

chop

See Identifiers see Comments

Conditionals and Loops
======================

In if and while requests, there are several more operators available:

e
o
     True if the current page is even or odd numbered (respectively)

n
t
     True if the document is being processed by nroff (or an ascii device) or troff.

'XXX'YYY'
     True if the string XXX is equal to the string YYY. Other characters can be used in place of the single quotes. (Which?) The strings are `formatted' before being compared. (?)

rXXX
     True if there is a number register named XXX.

dXXX
     True if there is a string, macro, diversion, or request named XXX.

cCH
     True if there is a character CH available;  CH is either an ASCII character or a special character \(CH or \[CH]; the condition will also be true if CH has been defined by the char request.

if-else
-------

Troff has if-then-else constructs like other languages, although the formatting can be painful.

The if request is troff's if statement, it is called as .if EXPR ANYTHING, where EXPR is the expression to be evaluated, and ANYTHING (the remainder of the line) which will be executed if the EXPR evaluates to non-zero (true). ANYTHING will be interpreted as though it was on a line by itself. See Expressions, for more info.

Here are some examples:

     .if t .ls 2				\" double spacing in troff
     .if 0 .ab how'd this happen??

An if-then-else is written using two requests ie and el the first request is the if part and the latter is the else part.

     .ie
     .el

In many cases you will want more than one request to be executed as a result of any of these requests, this can be done using the \{ and \} escapes. The following example shows the possible ways to use these escapes.

     .ie t \{\
     .    ds lq ``
     .    ds rq ''
     .\}
     .el \
     .\{\
     .    ds lq "
     .    ds rq "\}
     .ds qq "

See Expressions

while
-----

Groff provides a looping construct using the while request, which is used much like the if (and related) requests. The first argument is an expression which will be evaluated. The while request will interpret the remainder of the line until the expression evaluates to 0 or false.

     .nr a 0 1
     .while (\na<9) \&\n+a,
     \&\n+a

The preceding example produces:

     1, 2, 3, 4, 5, 6, 7, 8, 9, 10

The break request will break out of a while loop. Be sure not to confuse this with the .br request. The continue request will finish the current iteration of a while loop.

See Expressions

Writing Macros
==============

A macro is a collection of text and embedded commands which can be invoked multiple times.  Macros are used for defining common operations. Macros are defined using the de request.  This request takes a name for the macro as the first argument.  Subsequent lines are copied into an internal buffer until the line .. is encountered.  The optional second argument to de can change this ending token.

For example, suppose at the beginning of each paragraph, you want cause a break, move down a partial line and indent the first line. Such a macro could be defined as follows:

     .de P
     .br
     .sp .8v
     ..

The am request works similarily to de except it appends onto the macro named by the first argument.  So, if we decide we want our previously P macro to actually do indented instead of block paragraphs we can add the necessary code to our existing macro.

     .am P
     .ti +5n
     ..

Macros can be aliased with the als request.

rn

rm

chop

Copy-in Mode
------------

When troff reads in the test for a macro or diversion it copies the text (including request lines) into an internal buffer, except for escapes.  Escapes will be converted into an internal form, except for \n, \$, \*, \\ and \RET which are evaluated and inserted into the text where the escape was located. This is known as copy-in mode.

What this means is that you can specify when these escapes are to be evaluated (copy-in time or time of use) by insulating the escapes with an extra backslash.

For example, the following will result in the numbers 20 and 10 being printed.

     .nr x 20
     .de y
     .nr x 10
     \&\nx
     \&\\nx
     ..
     .y

Parameters
----------

The arguments to a macro can be examined using a variety of escapes. The number of arguments is available in the .$ number register. Any individual argument can be retrieved with one of the following escapes:

The escapes \$N, \$(NN and \$[NNN] will result in the Nth, NNth or NNNth argument.  Macros can have a unlimited number of arguments. Note that due to copy-in mode, you will want to have two backslashes on these in actual use, since you do not want them interpolated until the macro is actually invoked.

The request shift will shift the arguments 1 position, or as many positions as specified by the first argument. After executing this request, argument I will become argument I-N; arguments 1 to N will no longer be available. Shifting by negative amounts is currently undefined.

In some cases you will want to just use all of the arguments at once. For example if you pass the arguments along to another macro. The \$* escape is the concatenation of all the arguments separated by spaces. A similar escape is \$@, which is the concatenation of all the arguments with each surrounded by double quotes, and separated by spaces.

The \$0 escape is the name by which the current macro was invoked.  The als request can make a macro have more than one name.

     .de vl
     .ie \\n(.$=1 .ds Vl Pre-Release Version
     .el          .ds Vl Version \\$3, \\$4.
     ..

This would be called as

     .vl $Id: groff.texinfo,v 1.1.1.1 2000/05/06 00:04:56 wsanchez Exp $

See Request Arguments

Page Motions
============

Motions up and down the page can be done with the sp request. However, this causes a break so that the actual effect is to move to the left margin and then to the specified location.

The request mk can be used to mark a location on a page, for movement to later.  This request takes a register name as an argument in which to store the current page location, with no argument it will store the location in an internal register. The results of this can be used later by the rt or the sp request.  The rt request will return upwards to the location given in the register name given as an argument, with no argument it will return to the location marked with the mk request

     ... dual column example ...

There are escapes which will give you much finer control of movements about the page.

The \v'E' will let you do arbitrary vertical motion from the current location on the page.  The argument E specifies the distance to move, positive is downwards and negative upwards.  The default unit for this escape is vertical spaces, v's.  Beware, however, that troff will leave text processing to continue wherever the motion ends, so if you don't want to interfere with text processing, make sure your motions are balanced.

There are some special case escapes for vertical motion.

\r
     move upwards 1v.

\u
     move upwards .5v.

\d
     move down .5v.

Horizontal motions can be done via the \h'E' escape. The expression E indicates how far to move: positive is rightwards and negative leftwards.

There are a number of special case escapes for horizontal motion:

\SP
     An unbreakable and unpadable (i.e. not expanded during filling) space. (Note: it is a backslash followed by a space.)

\~
     This produces an unbreakable space that stretches like a normal interword space when a line is adjusted.

\|
     a 1/6th em space.

\^
     a 1/12th em space.

\0
     a space the size of a digit.

\&
     A zero width space.

\)
     Like \& except that it behaves like a character declared with the cflags request to be transparent for the purposes of end of sentence recognition.

     ... tex logo example ...

Often you will want to do horizontal movement based on the width of some arbitrary text (e.g. given as an argument to a macro). For that, there is the escape \w'TEXT' which will interpolate to the width of the given TEXT in basic units.

     ... strlen example ...

Font changes may occur in TEXT and not affect current settings.

Also after use, \w sets several registers:

st
sb
     The highest and lowest point, respectively, in TEXT.

rst
rsb
     Like the st and sb registers, but takes account of the heights and depths of characters.

ct
     is set according to what kinds of characters occur in TEXT.

     0
          all short characters, no decenders or tall characters.

     1
          decender

     2
          tall character

     3
          both a decender and a tall character

ssc
     The amount of horizontal space (possibly negative) that should be added to the last character before a subscript.

skw
     How far to right of the center of the last character in the \w argument, the center of an accent from a roman font should  be placed over that character.

\k .k

Drawing Functions
=================

Groff provides a number of ways to draw lines, and other figures on the page.  Used in combination with the page motion commands (see Page Motions, for more info) you can draw a wide variety of figures.  However, for complex drawings these operations can be quite cumbersome, and it may be wise to use the pic preprocessor. See gpic, for more information.

All drawing is done via escapes.

The \l will draw a line rightwards from the current location. The full syntax for this escape is \l'LC', where L is the length of the line to be drawn, starting at the current location, positive numbers will draw to the right, and negative will draw towards the left.  This can also be specified absolutely (i.e. with a leading |) which will draw back to the begining of the line.

The optional second parameter C is a character to draw the line with.  If this second argument is not specified, troff will use the underscore character.

If you need to separate the two arguments (to prevent troff from interpreting a drawing character as a scaling indicator), you can separate them with \&.

And now, for a useful example:

     .de box
     \(br\\$*\(br\l'|0\(rn'\l'|0\(ul'
     ..

Note that this works by outputing a box rule (a vertical line), then the text given as an argument and then another box rule. Then the line drawing escapes both draw from the current location to the beginning of the input line.

Vertical lines are drawn using the \L escape.  It's parameters are specified the same as the \l escape.  If the length is positive, the movement will be downwards, and upwards for negative. The default character is the box rule character. As with the vertical motion escapes, text processing will blindly continue where the line ends.

     ...box macro...

More flexible drawing functions are available via the \D escape.  While the previous escapes will work on an ascii device, these escapes will not.

\D'l X Y'
     Draw a line from the current location to the relative point specified by X, Y.

          ...revised box macro...

\D'c D'
     Draw a circle with a diameter of D with the leftmost point at the current position.

\D'C D'
     Draw a solid circle with the same parameters as an outlined circle.

\D'e DX DY'
     Draw an ellipse with a horizontal diameter of DX and a vertical diameter of DY with the leftmost point at the current position.

\D'E DX DY'
     Draw a solid elipse with the same parameters as an outlined elipse.

\D'a DX1 DY1 DX2 DY2'
     Draw an arc clockwise from the current location through the two specified locations.

\D'~ DX1 DY1 DX2 DY2 ...'
     Draw a spline from the current location to DX1, DY1 and then to DX2, DY2, and so on.

\D'f N'
     Set the shade of gray to be used for filling solid objects to N; N must be an integer between 0 and 1000, where 0 corresponds solid white and 1000 to solid black, and values in between correspond to intermediate shades of gray.  This applies only to solid circles, solid ellipses and solid polygons.  By default, a level of 1000 will be used.

\D'p DX1 DY1 DX2 DY2 ...'
     Draw a polygon from the current location to DX1, DY1 and then to DX2, DY2 and so on.  When the specified data points are exhausted, a line is drawn back to the starting point.

          ... box example (yes, again)...

\D'P DX1 DY1 DX2 DY2 ...'
     Draw a solid polygon with the same parameters as an outlined polygon.

          ... shaded box example ...

\D't N'
     Set the current line thickness to N machine units. A value of zero selects the smallest available line thickness.

Current position

The \b escape will pile a sequence of characters vertically, and center it vertically on the current line. This can be used to build large brackets and braces.

     \b'\(lt\(bv\(lk\(bv\(lb'

Traps
=====

Traps are locations, which, when reached, will call a specified macro. These traps can occur at a given location on the page, at a given location in the current diversion, after a certain number of input lines or at the end of input.

Any of these traps can be changed after they have been set with the ch request.  The first arguemnt is the name of the trap or macro, and the second is the new value for that trap.

Page Location Traps
-------------------

Page location traps are frequently used for page headers and footers.  The following is a simple example of this.

     .de hd                          \" Page header
     'sp .5i
     .tl 'Title''date'
     'sp .3i
     ..
     .de fo                          \" Page footer
     'sp 1v
     .tl ''%''
     'bp
     ..
     .wh 0   hd                      \" top of the page
     .wh -1i fo                      \" one inch from bottom

The number register .t is the distance to the next trap.

The location of a trap can be changed later on with the ch request. The first argument is the name of the macro to be invoked at the trap and the second argument is the new location for the trap. This is useful when you are building up footnotes in a diversion, and you need to allow more space at the bottom of the page for them.

     ... (simplified) footnote example ...

The vpt request will enable vertical position traps if the argment is non-zero, disable them otherwise.  Vertical position traps are traps set by the wh or dt requests.  Traps set by the it request are not vertical position traps.  The parameter that controls whether vertical position traps are enabled is global. Initially vertical position traps are enabled.  The current setting of this is available in the number register .vpt.

The number register .trunc contains the amount of vertical space truncated by the most recently sprung vertical position trap, or, if the trap was sprung by a ne request, minus the amount of vertical motion produced by the ne request.  In other words, at the point a trap is sprung, it represents the difference of what the vertical position would have been but for the trap, and what the vertical position actually is.

The number register .ne contains the amount of space that was needed in the last ne request that caused a trap to be sprung.  Useful in conjunction with the .trunc register.  See Page Control, for more information.

Diversion Traps
---------------

Traps can also be set within a diversion using the dt request.  Like wh the first argument is the location of the trap and the second argument is the name of the macro to be invoked. The number register .t will still work within diversions. See Diversions, for more information.

Input Line Traps
----------------

The it request will set an input line trap.  The format for calling this is .it N NAME, where N is the number of lines of input which may be read before springing the trap, NAME is the macro to be invoked.  Request lines are not counted as input lines.

For example, one possible use is to have a macro which will print the next N lines in a bold font.

     .de B
     .it B-end \\$1
     .ft B
     ..
     .de B-end
     .ft R
     ..

End-of-input Traps
------------------

The em request will set a trap at the end of input. The macro specified as an arguement will be executed after the last line of the input file has been processed.

For example, if your document had to have a section at the bottom of the last page for someone to approve you document, you could set it up with em.

     .de approval
     .ne 5v
     .sp |(\\n(.t-6v)
     .in +4i
     .lc _
     .br
     Approved:\t\a
     .sp
     Date:\t\t\a
     ..
     .em approval

Diversions
==========

In Troff you can divert text into a named storage area, due to the similarity to defining macros it is sometimes said to be stored in a macro.  This is used for saving text for output at a later time, which is useful for keeping blocks of text on the same page, footnotes, tables of contents and indexes.

Diversion is initiated by the di request, like the de request it takes an argument of a macro name to divert subsequent text to into.  The da macro will append to an existing diversion.

     ... end-note example ...

Diversions may be nested. The number register .z contains the name of the current diversion. The number register .d contains the current vertical place in the diversion.  If not in a diversion it is the same as the register nl. .h

After compleating a diversion, the builtin number registers dn and dl contain the vertical and horizontal size of the diversion.

     .\" Center text both horizontally & vertically
     .de (c
     .br
     .nf
     .di @c
     ..
     .de )c
     .br
     .di
     .nr @s (((\\n(.tu-\\n(dnu)/2u)-1v)
     .sp \\n(@su
     .ce 1000
     .nf
     .
     .br
     .ce 0
     .sp \\n(@su
     .br
     .fi
     .rr @s
     ..

Requests, macros and escapes are interpreted when read into a diversion. There are two ways to prevent this, either way will take the given text and transparently embed it into the diversion. The first method is to prefix the line with \!.  This will cause the entire line to be transparently inserted into the diversion. This is useful for macros you do not want invoked until the diverted text is actually output.

The other way is to surround the text by the \? escape, i.e. \?ANYTHING\?. ANYTHING may not  contain newlines; use \! if you want to embed newlines in a diversion.  The escape sequence \? is also recognised in copy mode and turned into a single internal code; it is this code that terminates anything.  Thus the followin example will print 4.

     .nr x 1
     .nf
     .di d
     \?\\?\\\\?\\\\\\\\nx\\\\?\\?\?
     .di
     .nr x 2
     .di e
     .d
     .di
     .nr x 3
     .di f
     .e
     .di
     .nr x 4
     .f

rn

rm

als

chop

asciify This request only exists in order to make it possible to make certain gross hacks work with GNU troff.  It unformats the diversion specified as an argument in such a way that ASCII characters that were formatted and diverted will be treated like ordinary input characters when the diversion is reread.  For example, the following will set register n to 1.

     .tr  @.
     .di  x
     @nr\  n\  1
     .br
     .di
     .tr  @@
     .asciify  x
     .x

See Copy-in Mode

Environments
============

Often you will need to print some text in a certain format regardless of what may be in effect at the time, for example, in a trap invoked macro to print headers and footers. To solve this groff has environments in which text is processed. An environment contains most of the parameters that control text processing.  You can switch amongst these environments, by default groff processes text in environment 0. The following is the information kept in an environment.

  * Type size

  * Font (family and style)

  * Page parameters

  * Fill/adjust mode

  * Tab stops

  * Partially collected lines

These environments may be given arbitrary names (see Identifiers, for more info.) Old versions of troff only had environments named 0, 1 and 2.

The ev request will switch among these environments. The single argument is the name of the environment to switch to, with no argument groff will switch back to the previous enviroment. There is no limit on the number of named environments; they will be created the first time that they are referenced. The .ev number register contains the name or number of the current environment.  This is a string-valued register.

     ... page break macro, revised ...

     .ev footnote-env
     .fam N
     .ps 6
     .vs 8
     .ll -.5i
     .ev
     ...
     .ev footnote-env
     \(dg Note the large, friendly letters.
     .ev

I/O
===

The so request will read in the file given as an argument and include it in place of the so request.  This is quite useful for large documents, i.e. keeping each chapter in a separate file. See gsoelim, for more information.

The mso request is the same as the so request except that file is searched for in the same way that tmac.NAME is searched for when the -mNAME option is specified.

The cf and trf requests are to include a file. It will transparently output the contents of file filename.  Each line is output as it would be were it preceded by \!; however, the lines are not subject to copy-mode interpretation.  If the file does not end with a newline, then a newline will be added.  For example, you can define a macro x containing the contents of file f, using

     .di x
     .trf f
     .di

.cf filename When  used  in  a  diversion, this will embed in the diversion an object which,  when  reread,  will  cause  the  contents  of  filename  to   be transparently copied through to the output.  In UNIX troff, the contents of filename is immediately copied through to the  output  regardless  of whether  there  is  a  current diversion; this behaviour is so anomalous that it must be considered a bug.

With trf, unlike cf, the file cannot contain characters such as NUL that are not legal troff input characters.

The nx request will force groff to continue processing of the file specified as an argument.

The rd request will read from standard input, and include what is read as though it were part of the input file.  Text is read until a blank line is encountered.

Using these two requests you can set up form letters. The form letter template is constructed like this:

     .ce
     \*(td
     .sp 2
     .nf
     .rd
     .sp
     .rd
     .fi
     Body of letter.
     .bp
     .nx repeat.let

When this is run, the following file should be redirected in. Note that requests included in this file are executed as though they were part of the form letter.  The last block of input is the ex requests which tells groff to stop processing.  If this was not there, groff would not know when to stop.

     Trent A. Fisher
     708 NW 19th Av., #202
     Portland, OR  97209

     Dear Trent,

     Len Adollar
     4315 Sierra Vista
     San Diego, CA  92103

     Dear Mr. Adollar,

     .ex

pi

The sy request will allow arbitrary system commands to be executed from within a groff document.  The output is not saved anyplace, so it is up to you to do so.

For example, the following example will introduce the current time into your document:

     .sy perl -e 'printf ".nr H %d\\n.nr M %d\\n.nr S %d\\n",\
     	     (localtime(time))[2,1,0]' > /tmp/x\n[$$]
     .so /tmp/x\n[$$]
     .sy rm /tmp/x\n[$$]
     \nH:\nM:\nS

Note that this works by having the perl script (run by sy) print out the nr requests which will set the number registers H, M and S, and then reads those commands in with the so request.

The systat number register contains The return value of the system() function executed by the last sy request.

The open request will open a file (specified as the second argument) for writing and associate the stream (specified as the first argument) with it.

The opena is like open, but if filename exists, append to it instead of truncating it.

The write request will write to the file associated with the stream specified by the first argument.  The stream must previously have been the subject of an open request.  The remainder of the line in interpreted as the ds request reads its second argument: a leading " will be stripped, and it will be read in copy-in mode.

The close request will close the stream specified by the first argument; stream will no longer be an acceptable argument to the write request.

     ... example of open write &c...

The \V escape will interpolate the contents of the specified environment variable, as returned by getenv(3). The argument to \V is specified as an identifier, i.e. \VX, \V(XX or \V[XXX]. \V is interpreted in copy-in mode.

Postprocessor Access
====================

There are two escapes which will allow you to give information directly to the postprocessor.  This is particularly useful for embedding PostScript into your final document.

The \X escape will embed its argument into the gtroff output preceded with x X.

The \Y escape is called with an identifier (i.e. \YX, \Y(XX or \Y[XXX]). This is approximately equivalent to \X'\*[XXX]'. However the contents of the string or macro XXX are not interpreted; also it is permitted for XXX to have been defined as a macro and thus contain newlines (it is not permitted for the argument to \X to contain newlines). The inclusion of newlines requires an extetension to the UNIX troff output format, and will confuse drivers that do not know about this extension.

See Devices

Miscellany
==========

This section contains parts of troff which cannot (yet) be categorized elsewhere in this manual.

Line numbers can be printed in the left margin using the nm request. The first argument is the line number of the next output line, this defaults to 1. The second argument indicates on which lines numbers will be printed, i.e. 5 means put line numbers on every 5 lines, this defaults to 1. The third argument is the space to be left between the number and your text, this defaults to 1. The fourth argument is the indentation of the line numbers. Without arguments, line numbers are turned off.

The nn request will temporarily turn off line numbering. The first argument is the number of lines not to be numbered, this defaults to 1. (does this disable incrementing or display?)

     ... line numbering example ...

margin characters can be automatically printed to the right of your text with the mc request. The first argument is the character to be printed and the second argument is the distance away from your text. With no arguments the margin characters are turned off. If this occurs before a break, no margin character will be printed.

This is quite useful for indicating text that has changed, and, in fact, there are programs available for doing this (they are called nrchbar and changebar and can be found in any comp.sources.unix archive.

     ... margin char example ...

The lf primary reason for existence is to make debugging documents which are split into many files, which are then put together with soelim and other preprocessors. The first argument is the name of the file and the second argument is the input line number in that file. This way troff can produce error messages which are intelligible to the user.

     ... example of soelim'ed doc ...

Debugging
=========

Troff is not easy to debug, but there are some useful features and strategies for debugging.

  * The tm request will send output to stderr, this is very useful for printing debugging output.

  * When doing something involved it is useful to leave the debugging statements in the code and have them turned on by a command line flag.

          .if \n(DB .tm debugging output

     Then you can activate these statements with:

          groff -rDB=1 file

  * The ab request is similar to the tm request, except that it will cause groff to stop processing. With no argument it will print User Abort.

  * The ex request will also cause groff to stop processing.

  * If you know you are going to get many errors and no useful output, you can tell groff to suppress formatted output with the -z flag.

  * The pm request will dump out the entire symbol table.

  * The pnr request will print the names and contents of all currently defined number registers on stderr.

  * The ptr request will print the names and positions of all traps (not including input line traps and diversion traps) on stderr.  Empty slots in the page trap list are printed as well, because they can affect the priority of subsequently planted traps.

  * The fl request instructs groff to flush its output immediately. The intention is that this be used when using troff interactively. There is little other use for it.

  * The backtrace request will print a backtrace of the input stack on stderr.

  * Groff has command line options for printing out more warnings (-w) and for printing backtraces (-b) when a warning or an error occurs.  The most verbose level of warnings is -ww.

  * The warn request controls the level of warnings checked for. The one argument is the sum of the numbers associated with each warning that is to be enabled; all other warnings will be disabled. The number associated with each warning is listed below. For example, .warn 0 will disable all warnings, and .warn 1 will disable all warnings except that about missing characters.  If an argument is not given, all warnings will be enabled. The number register .warn contains the current warning level.

Warnings
--------

The warnings that can be given by troff are divided into the following categories.  The name associated with each warning is used by the -w and -W options; the number is used by the warn request, and by the .warn register.

char
1
     Non-existent characters.  This is enabled by default.

number
2
     Invalid numeric expressions.  This is enabled by default.

break
4
     In fill mode, lines which could not be broken so that their length was less than the line length.  This is enabled by default.

delim
8
     Missing or mismatched closing delimiters.

el
16
     Use of the el request with no matching ie request. See if-else, for more information.

scale
32
     Meaningless scaling indicators.

range
64
     Out of range arguments.

syntax
128
     Dubious syntax in numeric expressions.

di
256
     Use of di or da without an argument when there is no current diversion.

mac
512
     Use of undefined strings, macros and diversions. When an undefined string, macro or diversion is used, that string is automatically defined as empty.  So, in most cases, at most one warning will be given for each name.

reg
1024
     Use of undefined number registers.  When an undefined number register is used, that register is automatically defined to have a value of 0.  a definition is automatically made with a value of 0. So, in most cases, at most one warning will be given for use of a particular name.

tab
2048
     Use of a tab character where a number was expected.

right-brace
4096
     Use of \} where a number was expected.

missing
8192
     Requests that are missing non-optional arguments.

input
16384
     Illegal input characters.

escape
32768
     Unrecognized escape sequences.  When an unrecognized escape sequence is encountered, the escape character is ignored.

space
65536
     Missing space between a request or macro and its argument.  This warning will be given when  an undefined name longer than two characters is encountered, and the first two characters of the name make a defined name.  The request or macro will not be invoked. When this warning is given, no macro is automatically defined.  This is enabled by default. This warning will never occur in compatibility mode.

font
131072
     Non-existent fonts. This is enabled by default.

all
     All warnings except di, mac and reg. It is intended that this covers all warnings that are useful with traditional macro packages.

w
     All warnings.

Implementation Differences
==========================

GNU troff has a number of features which cause incompatibilites with documents written with old versions of troff.

Long names cause some incompatibilities.  UNIX troff will interpret

     .dsabcd

as defining a string ab with contents cd. Normally, GNU troff will interpret this as a call of a macro named dsabcd.  Also UNIX troff will interpret \*[ or \n[ as references to a string or number register called [.  In GNU troff, however, this will normally be interpreted as the start of a long name.  In compatibility mode GNU troff will interpret these things in the traditional way.  In compatibility mode, however, long names are not recognised.  Compatibility mode can be turned on with the -C command line option, and turned on or off with the cp request. The number register .C is 1 if compatibility mode is on, 0 otherwise.

GNU troff does not allow the use of the escape sequences \| \^ \& \} \{ \SP \' \` \- \_ \! \% \c in names of strings, macros, diversions, number registers, fonts or environments; UNIX troff does. The \A escape sequence may be helpful in avoiding use of these escape sequences in names.

Fractional pointsizes cause one noteworthy incompatibility.  In UNIX troff the ps request ignores scale indicators and so

     .ps 10u

will set the pointsize to 10 points, whereas in GNU troff it will set the pointsize to 10 scaled points. See Fractional Type Sizes, for more information.

In GNU troff there is a fundamental difference between unformatted, input characters, and formatted, output characters.  Everything that affects how an output character will be output is stored with the character; once an output character has been constructed it  is unaffected by any subsequent requests that are executed, including bd, cs, tkf, tr, or fp requests.  Normally output characters are constructed from input characters at the moment immediately before the character is added to the current output line.  Macros, diversions and strings are all, in fact, the same type of object; they contain lists of input characters and output characters in any combination.  An  output character does not behave like an input character for the purposes of macro processing; it does not inherit any of the special properties that the input character from which it was constructed might have had. For example,

     .di x
     \\\\
     .br
     .di
     .x

will print \\ in GNU troff; each pair of input backslashes is turned into one output backslash and the resulting output backslashes are not interpreted as escape characters when they are reread. UNIX troff would interpret them as escape characters when they were reread and would end up printing one \. The correct way to obtain a printable backslash is to use the \e escape sequence: this will always print a single instance of the current escape character, regardless of whether or not it is used in a diversion; it will also work in both GNU troff and UNIX troff. If you wish for some reason to store in a diversion an escape sequence that will be interpreted when the diversion is reread, you can either use the traditional \! transparent output facility, or, if this is unsuitable, the new \? escape sequence.  See Diversions, for more information.

Summary
=======

geqn
****

Invoking geqn
=============

gtbl
****

Invoking gtbl
=============

gpic
****

Invoking gpic
=============

grap
****

grefer
******

Invoking grefer
===============

gsoelim
*******

Invoking gsoelim
================

Devices
*******

Special Characters
==================

See Font Files

grotty
======

Invoking grotty
---------------

grops
=====

Invoking grops
--------------

Embedding PostScript
--------------------

grodvi
======

Invoking grodvi
---------------

grolj4
======

Invoking grolj4
---------------

grohtml
=======

Invoking grohtml
----------------

gxditview
=========

Invoking gxditview
------------------

File formats
************

gtroff Output
=============

This section describes the format output by GNU troff.  The output format used by GNU troff is very similar to that used by UNIX device-independent troff.

The output format is ascii based, as opposed to a binary format (like TeX dvi). The output format is 8 bit clean, thus single characters can have the eighth bit set, as can the names of fonts and special characters.

The output format consists of single command characters with attached parameters which are separated from subsequent text by whitespace, or a newline.

The names of characters and fonts an be of arbitrary length; drivers should not assume that they will be only two characters long (as device-independent troff did).

When a character is to be printed, that character will always be in the current font. Unlike device-independent troff, it is not necessary for drivers to search special fonts to find a character.

HN

VN

hN

vN

cN

CN

NNC

tXXX
     XXX is any sequence of characters terminated by a space or a newline; the first character should be printed at the current position, the the current horizontal position should be increased by the width of the first character, and so on for each character. The width of the character is that given in the font file, appropriately scaled for the current point size, and rounded so that it is a multiple of the horizontal resolution. Special characters cannot be printed using this command.

     This command is only allowed if the tcommand line is present in the DESC file.

uN XXX
     This is same as the t command except that after printing each character, the current horizontal position is increased by the sum of the width of that character and n.

     This command is only allowed if the tcommand line is present in the DESC file.

nAB

pN

sN
     The argument to the s command is in scaled points (units of points/n, where n is the argument to the sizescale command  in the DESC file.)

fN

x ... \n
     Device control.

DC X...\n

Device Control
--------------

The x command is normally followed by a letter or word indicating the function to perform, followed by white space separated arguments.

The first argument can be abreviated to the first letter.

x init

x T

x res N H V

x H
     The argument to the x Height command is also in scaled points.

The first three output commands are guaranteed to be:

     x T device
     x res n h v
     x init

For example, the input crunchy \fH\s+2frog\s0\fP!? will produce:

     ... sample output here ...

Drawing Functions
-----------------

The D drawing command has been extended.  These extensions will only be used by GNU pic if the -x option is given.

     ...

Df n\n
     Set the shade of gray to be used for filling solid objects to n; n must be an integer between 0 and 1000, where 0 corresponds solid white and 1000 to solid black, and values in between correspond to intermediate shades of gray.  This applies only to solid circles, solid ellipses and solid polygons.  By default, a level of 1000 will be used.  Whatever color a solid object has, it should completely obscure everything beneath it. A value greater than 1000 or less than 0 can also be used: this means fill with the shade of gray that is currently being used for lines and text.  Normally this will be black, but some drivers may provide a way of changing this.

DC d\n
     Draw a solid circle with a diameter of d with the leftmost point at the current position.

DE dx dy\n
     Draw a solid ellipse with a horizontal diameter of dx and a vertical diameter of dy with the leftmost point at the current position.

Dp $dx sub 1$ $dy sub 1$ $dx sub 2$ $dy sub 2$ $...$ $dx sub n$ $dy sub
     n$\n Draw a polygon with, for $i = 1 ,..., n+1$, the i-th vertex at the current position $+ sum from j=1 to i-1 ( dx sub j , dy sub j )$. At the moment, GNU pic only uses this command to generate triangles and rectangles.

DP $dx sub 1$ $dy sub 1$ $dx sub 2$ $dy sub 2$ $...$ $dx sub n$ $dy sub
     n$\n Like Dp but draw a solid rather than outlined polygon.

Dt n\n
     Set the current line thickness to n machine units.  Traditionally UNIX troff drivers use a line thickness proportional to the current point size; drivers should continue to do this if no Dt command has been given, or if a Dt command has been given with a negative value of n.  A zero value of n selects the smallest available line thickness.

A difficulty arises in how the current position should be changed after the execution of these commands. This is not of great importance since the code generated by GNU pic does not depend on this. Given a drawing command of the form

\D'c $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$'

where c is not one of c, e, l, a or ~, UNIX troff will treat each of the $x sub i$ as a horizontal quantity, and each of the $y sub i$ as a vertical quantity and will assume that the width of the drawn object is $sum from i=1 to n x sub i$, and that the height is $sum from i=1 to n y sub i$.  (The assumption about the height can be seen by examining the st and sb registers after using such a D command in a \w escape sequence.)  This rule also holds for all the original drawing commands with the exception of De.  For the sake of compatibility GNU troff also follows this rule, even though it produces an ugly result in the case of the Df, Dt, and, to a lesser extent, DE commands.  Thus after executing a D command of the form

Dc $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$\n

the current position should be increased by $( sum from i=1 to n x sub i , sum from i=1 to n y sub i )$.

Line Continuation
-----------------

There is a continuation convention which permits the argument to the x X command to contain newlines: when outputting the argument to the x X command,  GNU troff will follow each newline in the argument with a + character (as usual, it will terminate the entire argument with a newline); thus if the line after the line containing the x X command starts with +, then the newline ending the line containing the x X command should be treated as part of the argument to the x X command, the + should be ignored, and the part of the line following the + should be treated like the part of the line following the x X command.

Font Files
==========

The groff font format is roughly a superset of the ditroff font format.  Unlike the ditroff font format, there is no associated binary format.  The font files for device name are stored in a directory devNAME.  There are two types of file: a device description file called DESC and for each font F a font file called F.  These are text files; there is no associated binary format.

DESC file format
----------------

The DESC file can contain the following types of line:

res N
     There are N machine units per inch.

hor N
     The horizontal resolution is N machine units.

vert N
     The vertical resolution is N machine units.

sizescale N
     The scale factor for pointsizes.  By default this has a value of 1.  One scaled point is equal to one point/N.  The arguments to the unitwidth and sizes commands are given in scaled points. See Fractional Type Sizes, for more information.

unitwidth N
     Quantities in the font files are given in machine units for fonts  whose point size is N scaled points.

tcommand
     This means that the postprocessor can handle the t and u output commands.

sizes S1 S2...SN 0
     This means that the device has fonts at S1, S2, ...SN scaled points.  The list of sizes must be terminated by a 0.  Each SI can also be a range of sizes M-N.  The list can extend over more than one line.

styles S1 S2...SM
     The first M font positions will be associated with styles S1...SM.

fonts N F1 F2 F3...FN
     Fonts F1...FN will be mounted in the font positions M+1, ..., M+N where M is the number of styles.  This command may extend over more than one line. A font name of 0 will cause no font to be mounted on the corresponding font position.

family FAM
     The default font family is FAM.

charset
     This line and everything following in the file are ignored.  It is allowed for the sake of backwards compatibility.

The res, unitwidth, fonts and sizes lines are compulsory.  Other commands are ignored by troff but may be used by postprocessors to store arbitrary information about the device in the DESC file.

Font file format
----------------

A font file has two sections.  The first section is a sequence of lines each containing a sequence of blank delimited words; the first word in the line is a key, and subsequent words give a value for that key.

name F
     The name of the font is F.

spacewidth N
     The normal width of a space is N.

slant N
     The characters of the font have a slant of N degrees. (Positive means forward.)

ligatures LIG1 LIG2...LIGN [0]
     Characters LIG1, LIG2, ..., LIGN are ligatures; possible ligatures are ff, fi, fl and ffl.  For backwards compatibiliy, the list of ligatures may be terminated with a 0.  The list of ligatures may not extend over more than one line.

special
     The font is special; this means that when a character is requested that is not present in the current font, it will be searched for in any special fonts that are mounted.

Other commands are ignored by troff but may be used by postprocessors to store arbitrary information about the font in the font file.

The first section can contain comments which start with the # character and extend to the end of a line.

The second section contains one or two subsections.  It must contain a charset subsection and it may also contain a kernpairs subsection.  These subsections can appear in any order.  Each subsection starts with a word on a line by itself.

The word charset starts the charset subsection. The charset line is followed by a sequence of lines. Each line gives information for one character.  A line comprises a number of fields separated by blanks or tabs. The format is

     NAME METRICS TYPE CODE COMMENT

NAME identifies the character: if NAME is a single character C then it corresponds to the groff input character C; if it is of the form \C where C is a single character, then it corresponds to the groff input character \C; otherwise it corresponds to the groff input character \[NAME] (if it is exactly two characters XX it can be entered as \(XX.) Groff supports eight bit characters; however some utilities has difficulties with eight bit characters. For this reason, there is a convention that the NAME charN is equivalent to the single character whose code is N. For example, char163 would be equivalent to the character with CODE 163 which is the pounds sterling sign in ISO Latin-1 character set.  The name --- is special and indicates that the character is unnamed; such characters can only be used by means of the \N escape sequence in troff.

The TYPE field gives the character type:

1
     means the character has an descender, for example, p;

2
     means the character has an ascender, for example, b;

3
     means the character has both an ascender and a descender, for example, (.

The CODE field gives the code which the postprocessor uses to print the character.  The character can also be input to groff using this code by means of the \N escape sequence. The code can be any integer.  If it starts with a 0 it will be interpreted as octal; if it starts with 0x or 0X it will be intepreted as hexdecimal.

Anything on the line after the CODE field will be ignored.

The METRICS field has the form:

     WIDTH[,HEIGHT[,DEPTH[,ITALIC_CORRECTION[,LEFT_ITALIC_CORRECTION[,SUBSCRIPT_CORRECTION]]]]]

There must not be any spaces between these subfields.  Missing subfields are assumed to be 0.  The subfields are all decimal integers.  Since there is no associated binary format, these values are not required to fit into a variable of type char as they are in ditroff.  The WIDTH subfields gives the width of the character.  The HEIGHT subfield gives the height of the character (upwards is positive); if a character does not extend above the baseline, it should be given a zero height, rather than a negative height.  The DEPTH subfield gives the depth of the character, that is, the distance below the lowest point below the baseline to which the character extends (downwards is positive); if a character does not extend below above the baseline, it should be given a zero depth, rather than a negative depth.  The ITALIC_CORRECTION subfield gives the amount of space that should be added after the character when it is immediately to be followed by a character from a roman font.  The LEFT_ITALIC_CORRECTION subfield gives the amount of space that should be added before the character when it is immediately to be preceded by a character from a roman font.  The SUBSCRIPT_CORRECTION gives the amount of space that should be added after a character before adding a subscript. This should be less than the italic correction.

A line in the charset section can also have the format

     NAME "

This indicates that NAME is just another name for the character mentioned in the preceding line.

The word kernpairs starts the kernpairs section.  This contains a sequence of lines of the form:

     C1 C2 N

This means that when character C1 appears next to character C2 the space between them should be increased by N.  Most entries in kernpairs section will have a negative value for N.

Installation
************

String Index
************

Macro Index
***********