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