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|
--- /dev/null
+++ b/miscutils/lock.c
@@ -0,0 +1,155 @@
+/*
+ * Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
+ *
+ * This is free software, licensed under the GNU General Public License v2.
+ */
+
+//config:config LOCK
+//config: bool "lock"
+//config: default n
+//config: help
+//config: Small utility for using locks in scripts
+
+//applet:IF_LOCK(APPLET(lock, BB_DIR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_LOCK) += lock.o
+
+//usage:#define lock_trivial_usage NOUSAGE_STR
+//usage:#define lock_full_usage ""
+
+#include <sys/types.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include "busybox.h"
+
+static int unlock = 0;
+static int shared = 0;
+static int waitonly = 0;
+static int try_lock = 0;
+static int fd;
+static char *file;
+
+static void usage(char *name)
+{
+ fprintf(stderr, "Usage: %s [-suw] <filename>\n"
+ " -s Use shared locking\n"
+ " -u Unlock\n"
+ " -w Wait for the lock to become free, don't acquire lock\n"
+ " -n Don't wait for the lock to become free. Fail with exit code\n"
+ "\n", name);
+ exit(1);
+}
+
+static void exit_unlock(int sig)
+{
+ flock(fd, LOCK_UN);
+ exit(0);
+}
+
+static int do_unlock(void)
+{
+ FILE *f;
+ int i;
+
+ if ((f = fopen(file, "r")) == NULL)
+ return 0;
+
+ fscanf(f, "%d", &i);
+ if (i > 0)
+ kill(i, SIGTERM);
+
+ fclose(f);
+
+ return 0;
+}
+
+static int do_lock(void)
+{
+ int pid;
+ int flags;
+ char pidstr[8];
+
+ if ((fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0700)) < 0) {
+ if ((fd = open(file, O_RDWR)) < 0) {
+ fprintf(stderr, "Can't open %s\n", file);
+ return 1;
+ }
+ }
+
+ flags = shared ? LOCK_SH : LOCK_EX;
+ flags |= try_lock ? LOCK_NB : 0;
+
+ if (flock(fd, flags) < 0) {
+ fprintf(stderr, "Can't lock %s\n", file);
+ return 1;
+ }
+
+ pid = fork();
+
+ if (pid < 0)
+ return -1;
+
+ if (pid == 0) {
+ signal(SIGKILL, exit_unlock);
+ signal(SIGTERM, exit_unlock);
+ signal(SIGINT, exit_unlock);
+ if (waitonly)
+ exit_unlock(0);
+ else
+ while (1)
+ sleep(1);
+ } else {
+ if (!waitonly) {
+ lseek(fd, 0, SEEK_SET);
+ ftruncate(fd, 0);
+ sprintf(pidstr, "%d\n", pid);
+ write(fd, pidstr, strlen(pidstr));
+ close(fd);
+ }
+
+ return 0;
+ }
+ return 0;
+}
+
+int lock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int lock_main(int argc, char **argv)
+{
+ char **args = &argv[1];
+ int c = argc - 1;
+
+ while ((*args != NULL) && (*args)[0] == '-') {
+ char *ch = *args;
+ while (*(++ch) > 0) {
+ switch(*ch) {
+ case 'w':
+ waitonly = 1;
+ break;
+ case 's':
+ shared = 1;
+ break;
+ case 'u':
+ unlock = 1;
+ break;
+ case 'n':
+ try_lock = 1;
+ break;
+ }
+ }
+ c--;
+ args++;
+ }
+
+ if (c != 1)
+ usage(argv[0]);
+
+ file = *args;
+ if (unlock)
+ return do_unlock();
+ else
+ return do_lock();
+}
|
