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-rw-r--r--pidfile.c130
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+/*
+ pidfile.c - interact with pidfiles
+ Copyright (c) 1995 Martin Schulze <Martin.Schulze@Linux.DE>
+
+ This file is part of the sysklogd package, a kernel and system log daemon.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA
+*/
+
+/*
+ * Sat Aug 19 13:24:33 MET DST 1995: Martin Schulze
+ * First version (v0.2) released
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/file.h>
+#include <string.h>
+#include <errno.h>
+#include <signal.h>
+
+/* read_pid
+ *
+ * Reads the specified pidfile and returns the read pid.
+ * 0 is returned if either there's no pidfile, it's empty
+ * or no pid can be read.
+ */
+int read_pid (char *pidfile)
+{
+ FILE *f;
+ int pid;
+
+ if (!(f=fopen(pidfile,"r")))
+ return 0;
+ fscanf(f,"%d", &pid);
+ fclose(f);
+ return pid;
+}
+
+/* check_pid
+ *
+ * Reads the pid using read_pid and looks up the pid in the process
+ * table (using /proc) to determine if the process already exists. If
+ * so 1 is returned, otherwise 0.
+ */
+int check_pid (char *pidfile)
+{
+ int pid = read_pid(pidfile);
+
+ /* Amazing ! _I_ am already holding the pid file... */
+ if ((!pid) || (pid == getpid ()))
+ return 0;
+
+ /*
+ * The 'standard' method of doing this is to try and do a 'fake' kill
+ * of the process. If an ESRCH error is returned the process cannot
+ * be found -- GW
+ */
+ /* But... errno is usually changed only on error.. */
+ if (kill(pid, 0) && errno == ESRCH)
+ return(0);
+
+ return pid;
+}
+
+/* write_pid
+ *
+ * Writes the pid to the specified file. If that fails 0 is
+ * returned, otherwise the pid.
+ */
+int write_pid (char *pidfile)
+{
+ FILE *f;
+ int fd;
+ int pid;
+
+ if ( ((fd = open(pidfile, O_RDWR|O_CREAT, 0644)) == -1)
+ || ((f = fdopen(fd, "r+")) == NULL) ) {
+ fprintf(stderr, "Can't open or create %s.\n", pidfile);
+ return 0;
+ }
+
+ if (flock(fd, LOCK_EX|LOCK_NB) == -1) {
+ fscanf(f, "%d", &pid);
+ fclose(f);
+ printf("Can't lock, lock is held by pid %d.\n", pid);
+ return 0;
+ }
+
+ pid = getpid();
+ if (!fprintf(f,"%d\n", pid)) {
+ printf("Can't write pid , %s.\n", strerror(errno));
+ close(fd);
+ return 0;
+ }
+ fflush(f);
+
+ if (flock(fd, LOCK_UN) == -1) {
+ printf("Can't unlock pidfile %s, %s.\n", pidfile, strerror(errno));
+ close(fd);
+ return 0;
+ }
+ close(fd);
+
+ return pid;
+}
+
+/* remove_pid
+ *
+ * Remove the the specified file. The result from unlink(2)
+ * is returned
+ */
+int remove_pid (char *pidfile)
+{
+ return unlink (pidfile);
+}
+