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/* |
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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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|
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This file is part of the sysklogd package, a kernel and system log daemon. |
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|
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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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|
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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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|
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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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/* |
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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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|
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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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#include <sys/types.h> |
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#include <signal.h> |
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#include <fcntl.h> |
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|
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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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|
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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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|
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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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|
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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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/* |
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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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errno = 0; |
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if (kill(pid, 0) && errno == ESRCH) |
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return(0); |
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|
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return pid; |
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} |
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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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|
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if ( ((fd = open(pidfile, O_RDWR|O_CREAT, 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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|
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#ifdef HAVE_FLOCK |
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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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#endif |
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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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|
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#ifdef HAVE_FLOCK |
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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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#endif |
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close(fd); |
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|
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return pid; |
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} |
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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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|
