141 lines
3.3 KiB
C
141 lines
3.3 KiB
C
/*
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pidfile.c - interact with pidfiles
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Copyright (c) 1995 Martin Schulze <Martin.Schulze@Linux.DE>
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This file is part of the sysklogd package, a kernel and system log daemon.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA
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*/
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/*
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* Sat Aug 19 13:24:33 MET DST 1995: Martin Schulze
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* First version (v0.2) released
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/file.h>
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#include <string.h>
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#include <errno.h>
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#include <signal.h>
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/* read_pid
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*
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* Reads the specified pidfile and returns the read pid.
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* 0 is returned if either there's no pidfile, it's empty
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* or no pid can be read.
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*/
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int read_pid (char *pidfile)
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{
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FILE *f;
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int pid;
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if (!(f=fopen(pidfile,"r")))
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return 0;
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fscanf(f,"%d", &pid);
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fclose(f);
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return pid;
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}
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/* check_pid
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*
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* Reads the pid using read_pid and looks up the pid in the process
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* table (using /proc) to determine if the process already exists. If
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* so 1 is returned, otherwise 0.
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*/
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int check_pid (char *pidfile)
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{
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int pid = read_pid(pidfile);
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/* Amazing ! _I_ am already holding the pid file... */
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if ((!pid) || (pid == getpid ()))
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return 0;
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/*
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* The 'standard' method of doing this is to try and do a 'fake' kill
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* of the process. If an ESRCH error is returned the process cannot
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* be found -- GW
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*/
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/* But... errno is usually changed only on error.. */
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if (kill(pid, 0) && errno == ESRCH)
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return(0);
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return pid;
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}
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/* write_pid
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*
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* Writes the pid to the specified file. If that fails 0 is
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* returned, otherwise the pid.
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*/
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int write_pid (char *pidfile)
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{
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FILE *f;
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int fd;
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int pid;
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if ( ((fd = open(pidfile, O_RDWR|O_CREAT|O_TRUNC, 0644)) == -1)
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|| ((f = fdopen(fd, "r+")) == NULL) ) {
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fprintf(stderr, "Can't open or create %s.\n", pidfile);
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return 0;
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}
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if (flock(fd, LOCK_EX|LOCK_NB) == -1) {
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fscanf(f, "%d", &pid);
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fclose(f);
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printf("Can't lock, lock is held by pid %d.\n", pid);
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return 0;
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}
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pid = getpid();
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if (!fprintf(f,"%d\n", pid)) {
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printf("Can't write pid , %s.\n", strerror(errno));
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close(fd);
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return 0;
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}
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fflush(f);
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if (flock(fd, LOCK_UN) == -1) {
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printf("Can't unlock pidfile %s, %s.\n", pidfile, strerror(errno));
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close(fd);
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return 0;
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}
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close(fd);
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return pid;
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}
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/* touch_pid
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*
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* Touches the specified pidfile f.ex. when receiving a SIGHUP
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* The result from utimensat() is returned
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*/
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int touch_pid (char *pidfile)
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{
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return utimensat(0, pidfile, NULL, 0);
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}
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/* remove_pid
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*
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* Remove the the specified file. The result from unlink(2)
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* is returned
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*/
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int remove_pid (char *pidfile)
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{
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return unlink (pidfile);
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}
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