/*++ /* NAME /* open_lock 3 /* SUMMARY /* open or create file and lock it for exclusive access /* SYNOPSIS /* #include <open_lock.h> /* /* VSTREAM *open_lock(path, flags, mode, why) /* const char *path; /* int flags; /* mode_t mode; /* VSTRING *why; /* DESCRIPTION /* This module opens or creates the named file and attempts to /* acquire an exclusive lock. The lock is lost when the last /* process closes the file. /* /* Arguments: /* .IP "path, flags, mode" /* These are passed on to safe_open(). /* .IP why /* storage for diagnostics. /* SEE ALSO /* safe_open(3) carefully open or create file /* myflock(3) get exclusive lock on file /* DIAGNOSTICS /* In case of problems the result is a null pointer and a problem /* description is returned via the global \fIerrno\fR variable. /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ /* System library. */ #include <sys_defs.h> #include <unistd.h> #include <fcntl.h> /* Utility library. */ #include <msg.h> #include <vstream.h> #include <vstring.h> #include <safe_open.h> #include <myflock.h> #include <open_lock.h> /* open_lock - open file and lock it for exclusive access */ VSTREAM *open_lock(const char *path, int flags, mode_t mode, VSTRING *why) { VSTREAM *fp; /* * Carefully create or open the file, and lock it down. Some systems * don't have the O_LOCK open() flag, or the flag does not do what we * want, so we roll our own lock. */ if ((fp = safe_open(path, flags, mode, (struct stat *) 0, -1, -1, why)) == 0) return (0); if (myflock(vstream_fileno(fp), INTERNAL_LOCK, MYFLOCK_OP_EXCLUSIVE | MYFLOCK_OP_NOWAIT) < 0) { vstring_sprintf(why, "unable to set exclusive lock: %m"); vstream_fclose(fp); return (0); } return (fp); }