2 pidfile.c - interact with pidfiles
3 Copyright (c) 1995 Martin Schulze <Martin.Schulze@Linux.DE>
5 This file is part of the sysklogd package, a kernel and system log daemon.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License along
18 with this program; if not, write to the Free Software Foundation, Inc.,
19 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22 /* left unaltered for tinc -- Ivo Timmermans */
24 * Sat Aug 19 13:24:33 MET DST 1995: Martin Schulze
25 * First version (v0.2) released
35 * Reads the specified pidfile and returns the read pid.
36 * 0 is returned if either there's no pidfile, it's empty
37 * or no pid can be read.
39 pid_t read_pid (const char *pidfile)
44 if (!(f=fopen(pidfile,"r")))
46 if(fscanf(f,"%20ld", &pid) != 1)
54 * Reads the pid using read_pid and looks up the pid in the process
55 * table (using /proc) to determine if the process already exists. If
56 * so the pid is returned, otherwise 0.
58 pid_t check_pid (const char *pidfile)
60 pid_t pid = read_pid(pidfile);
62 /* Amazing ! _I_ am already holding the pid file... */
63 if ((!pid) || (pid == getpid ()))
67 * The 'standard' method of doing this is to try and do a 'fake' kill
68 * of the process. If an ESRCH error is returned the process cannot
71 /* But... errno is usually changed only on error.. */
73 if (kill(pid, 0) && errno == ESRCH)
81 * Writes the pid to the specified file. If that fails 0 is
82 * returned, otherwise the pid.
84 pid_t write_pid (const char *pidfile)
90 if ((fd = open(pidfile, O_RDWR|O_CREAT, 0644)) == -1) {
94 if ((f = fdopen(fd, "r+")) == NULL) {
100 if (flock(fd, LOCK_EX|LOCK_NB) == -1) {
107 if (!fprintf(f,"%ld\n", (long)pid)) {
114 if (flock(fd, LOCK_UN) == -1) {
126 * Remove the the specified file. The result from unlink(2)
129 int remove_pid (const char *pidfile)
131 return unlink (pidfile);