.\" $OpenBSD: ecvt.3,v 1.8 2007/05/31 19:19:31 jmc Exp $ .\" .\" Copyright (c) 2002 Todd C. Miller <Todd.Miller@courtesan.com> .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .\" Sponsored in part by the Defense Advanced Research Projects .\" Agency (DARPA) and Air Force Research Laboratory, Air Force .\" Materiel Command, USAF, under agreement number F39502-99-1-0512. .\" .Dd $Mdocdate: May 31 2007 $ .Dt ECVT 3 .Os .Sh NAME .Nm ecvt , .Nm fcvt , .Nm gcvt .Nd convert double to .Tn ASCII string .Sh SYNOPSIS .Fd #include <stdlib.h> .Ft char * .Fn ecvt "double value" "int ndigit" "int * restrict decpt" "int * restrict sign" .Ft char * .Fn fcvt "double value" "int ndigit" "int * restrict decpt" "int * restrict sign" .Ft char * .Fn gcvt "double value" "int ndigit" "char *buf" .Sh DESCRIPTION .Bf -symbolic These functions are provided for compatibility with legacy code. New code should use the .Xr snprintf 3 function for improved safety and portability. .Ef .Pp The .Fn ecvt , .Fn fcvt and .Fn gcvt functions convert the double precision floating-point number .Fa value to a NUL-terminated .Tn ASCII string. .Pp The .Fn ecvt function converts .Fa value to a NUL-terminated string of exactly .Fa ndigit digits and returns a pointer to that string. The result is padded with zeroes from left to right as needed. There are no leading zeroes unless .Fa value itself is 0. The least significant digit is rounded in an implementation-dependent manner. The position of the decimal point relative to the beginning of the string is stored in .Fa decpt . A negative value indicates that the decimal point is located to the left of the returned digits (this occurs when there is no whole number component to .Fa value ) . If .Fa value is zero, it is unspecified whether the integer pointed to by .Fa decpt will be 0 or 1. The decimal point itself is not included in the returned string. If the sign of the result is negative, the integer pointed to by .Fa sign is non-zero; otherwise, it is 0. .Pp If the converted value is out of range or is not representable, the contents of the returned string are unspecified. .Pp The .Fn fcvt function is identical to .Fn ecvt with the exception that .Fa ndigit specifies the number of digits after the decimal point (zero-padded as needed). .Pp The .Fn gcvt function converts .Fa value to a NUL-terminated string similar to the %g .Xr printf 3 format specifier and stores the result in .Fa buf . It produces .Fa ndigit significant digits similar to the %f .Xr printf 3 format specifier where possible. If .Fa ndigit does allow sufficient precision, the result is stored in exponential notation similar to the %e .Xr printf 3 format specifier. If .Fa value is less than zero, .Fa buf will be prefixed with a minus sign. A decimal point is included in the returned string if .Fa value is not a whole number. Unlike the .Fn ecvt and .Fn fcvt functions, .Fa buf is not zero-padded. .Sh RETURN VALUES The .Fn ecvt , .Fn fcvt and .Fn gcvt functions return a NUL-terminated string representation of .Fa value . .Sh WARNINGS The .Fn ecvt and .Fn fcvt functions return a pointer to internal storage space that will be overwritten by subsequent calls to either function. .Pp The maximum possible precision of the return value is limited by the precision of a double and may not be the same on all architectures. .Pp The .Xr snprintf 3 function is preferred over these functions for new code. .Sh SEE ALSO .Xr printf 3 , .Xr strtod 3 .Sh STANDARDS The .Fn ecvt , .Fn fcvt and .Fn gcvt functions conform to .St -p1003.1-2001 .