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/*++
/* NAME
/* dot_lockfile 3
/* SUMMARY
/* dotlock file management
/* SYNOPSIS
/* #include <dot_lockfile.h>
/*
/* int dot_lockfile(path, why)
/* const char *path;
/* VSTRING *why;
/*
/* void dot_unlockfile(path)
/* const char *path;
/* DESCRIPTION
/* dot_lockfile() constructs a lock file name by appending ".lock" to
/* \fIpath\fR and creates the named file exclusively. It tries several
/* times and attempts to break stale locks. A negative result value
/* means no lock file could be created.
/*
/* dot_unlockfile() attempts to remove the lock file created by
/* dot_lockfile().
/*
/* Arguments:
/* .IP path
/* Name of the file to be locked or unlocked.
/* .IP why
/* A null pointer, or storage for the reason why a lock file could
/* not be created.
/* CONFIGURATION PARAMETERS
/* deliver_lock_attempts, how many times to try to create a lock
/* deliver_lock_delay, how long to wait between attempts
/* stale_lock_time, when to break a stale lock
/* 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 <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <time.h>
/* Utility library. */
#include <vstring.h>
#include <stringops.h>
#include <mymalloc.h>
/* Global library. */
#include "mail_params.h"
#include "dot_lockfile.h"
/* dot_lockfile - create user.lock file */
int dot_lockfile(const char *path, VSTRING *why)
{
char *lock_file;
int count;
struct stat st;
int fd;
int status = -1;
lock_file = concatenate(path, ".lock", (char *) 0);
for (count = 0; /* void */ ; count++) {
if (count >= var_flock_tries)
break;
if (count > 0)
sleep(var_flock_delay);
/*
* Attempt to create the lock. This code relies on O_EXCL | O_CREAT
* to not follow symlinks.
*/
if ((fd = open(lock_file, O_WRONLY | O_EXCL | O_CREAT, 0)) >= 0) {
close(fd);
status = 0;
break;
}
/*
* We can deal only with "file exists" errors. Any other error means
* we better give up trying.
*/
if (errno != EEXIST)
break;
/*
* Break the lock when it is too old. Give up when we are unable to
* remove a stale lock.
*/
if (stat(lock_file, &st) == 0)
if (time((time_t *) 0) > st.st_ctime + var_flock_stale)
if (unlink(lock_file) < 0)
if (errno != ENOENT)
break;
errno = EEXIST;
}
if (status && why)
vstring_sprintf(why, "unable to create lock file %s: %m", lock_file);
myfree(lock_file);
return (status);
}
/* dot_unlockfile - remove .lock file */
void dot_unlockfile(const char *path)
{
char *lock_file;
lock_file = concatenate(path, ".lock", (char *) 0);
(void) unlink(lock_file);
myfree(lock_file);
}
#ifdef TEST
/*
* Test program for setting a .lock file.
*
* Usage: dot_lockfile filename
*
* Creates filename.lock and removes it.
*/
#include <msg.h>
#include <vstream.h>
#include <msg_vstream.h>
#include <mail_conf.h>
main(int argc, char **argv)
{
VSTRING *why = vstring_alloc(100);
msg_vstream_init(argv[0], VSTREAM_ERR);
if (argc != 2)
msg_fatal("usage: %s file-to-be-locked", argv[0]);
mail_conf_read();
if (dot_lockfile(argv[1], why) < 0)
msg_fatal("%s", vstring_str(why));
dot_unlockfile(argv[1]);
vstring_free(why);
return (0);
}
#endif
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