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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();
- +}
|
