--- /dev/null
+// $Id$ --*- c -*--
+
+// Copyright (C) 2004 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
+//
+// 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; version 2 of the License.
+//
+// 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 02111-1307, USA.
+
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "util.h"
+
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <time.h>
+#include <sys/file.h>
+
+static void
+showHelp(int fd, char const *cmd, int res)
+{
+ WRITE_MSG(fd, "Usage: ");
+ WRITE_STR(fd, cmd);
+ WRITE_MSG(fd,
+ " [--] <lockfile> <syncpipe> [<timeout>]\n\n"
+ "Protocol:\n"
+ " 1. parent (shell) creates a named <syncpipe>\n"
+ " 2. 'lockfile' will be called\n"
+ " 3a. 'lockfile' waits until somebody opens the <syncpipe> for reading\n"
+ " 3b. parent (shell) opens the pipe for reading and blocks\n"
+ " 4. 'lockfile' calls flock() on the <lockfile>\n"
+ " 5. 'lockfile' closes the <syncpipe>\n"
+ " 6. parent (shell) unlocks since <syncpipe> is closed\n"
+ " 7. 'lockfile' goes into infinite loop\n"
+ " 8. parent sends SIGHUP (or other signal) to 'lockfile\n"
+ "\n"
+ "Sample code:\n"
+ " tmp=$(mktemp /tmp/lock.XXXXXX)\n"
+ " rm -f $tmp # safe since mknod(2) does not follow symlinks\n"
+ " mkfifo $tmp\n"
+ " lockfile $lock $tmp &\n"
+ " cat <$tmp/sync >/dev/null\n"
+ " ... <actions> ...\n"
+ " kill -HUP $! # (implicated by shell-exit)\n"
+ "\n"
+ "Please report bugs to " PACKAGE_BUGREPORT "\n");
+ exit(res);
+}
+
+static void
+showVersion()
+{
+ WRITE_MSG(1,
+ "lockfile " VERSION " -- locks a file"
+ "This program is part of " PACKAGE_STRING "\n\n"
+ "Copyright (C) 2004 Enrico Scholz\n"
+ VERSION_COPYRIGHT_DISCLAIMER);
+ exit(0);
+}
+
+static volatile int timeout_flag = 0;
+
+static void
+alarmFunc(int UNUSED sig)
+{
+ timeout_flag = 1;
+ signal(SIGALRM, alarmFunc);
+}
+
+static void
+quitFunc(int UNUSED sig)
+{
+ _exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+ int fd, sync_fd;
+ int idx = 1;
+ time_t end_time;
+
+ if (argc>=2) {
+ if (strcmp(argv[1], "--help") ==0) showHelp(1, argv[0], 0);
+ if (strcmp(argv[1], "--version")==0) showVersion();
+ if (strcmp(argv[1], "--") ==0) ++idx;
+ }
+
+ if (argc<idx+2) {
+ WRITE_MSG(2, "Not enough parameters; use '--help' for more information\n");
+ return EXIT_FAILURE;
+ }
+
+ end_time = time(0);
+ if (argc==idx+3) end_time += atoi(argv[idx+2]);
+ else end_time += 300;
+
+
+
+ if ((fd=open(argv[idx], O_CREAT|O_RDONLY|O_NOFOLLOW|O_NONBLOCK, 0644))==-1)
+ perror("lockfile: open(<lockfile>)");
+ else if ((sync_fd=open(argv[idx+1], O_WRONLY))==-1)
+ perror("lockfile: open(<syncpipe>)");
+ else if (unlink(argv[idx+1])==-1)
+ perror("lockfile: unlink(<syncpipe>)");
+ else if (siginterrupt(SIGALRM, 1)==-1)
+ perror("lockfile: siginterrupt()");
+ else if (signal(SIGALRM, alarmFunc)==SIG_ERR ||
+ signal(SIGHUP, quitFunc)==SIG_ERR)
+ perror("lockfile: signal()");
+ else while (time(0)<end_time && getppid()!=1) {
+ alarm(1);
+ if (flock(fd,LOCK_EX)==-1) {
+ if (errno==EINTR) continue;
+ perror("lockfile: flock()");
+ return EXIT_FAILURE;
+ }
+
+ close(sync_fd);
+
+ signal(SIGALRM, SIG_IGN);
+ while (getppid()!=1) sleep(1);
+
+ return EXIT_SUCCESS;
+ }
+
+ return EXIT_FAILURE;
+}
+