--- a/include/applets.h +++ b/include/applets.h @@ -220,6 +220,7 @@ USE_LN(APPLET_NOEXEC(ln, ln, _BB_DIR_BIN USE_LOAD_POLICY(APPLET(load_policy, _BB_DIR_USR_SBIN, _BB_SUID_NEVER)) USE_LOADFONT(APPLET(loadfont, _BB_DIR_USR_BIN, _BB_SUID_NEVER)) USE_LOADKMAP(APPLET(loadkmap, _BB_DIR_SBIN, _BB_SUID_NEVER)) +USE_LOCK(APPLET(lock, _BB_DIR_BIN, _BB_SUID_NEVER)) USE_LOGGER(APPLET(logger, _BB_DIR_USR_BIN, _BB_SUID_NEVER)) USE_LOGIN(APPLET(login, _BB_DIR_BIN, _BB_SUID_ALWAYS)) USE_LOGNAME(APPLET_NOFORK(logname, logname, _BB_DIR_USR_BIN, _BB_SUID_NEVER, logname)) --- a/include/usage.h +++ b/include/usage.h @@ -2138,6 +2138,9 @@ #define loadkmap_example_usage \ "$ loadkmap < /etc/i18n/lang-keymap\n" +#define lock_trivial_usage NOUSAGE_STR +#define lock_full_usage "" + #define logger_trivial_usage \ "[OPTION]... [MESSAGE]" #define logger_full_usage "\n\n" \ --- a/miscutils/Config.in +++ b/miscutils/Config.in @@ -364,6 +364,12 @@ config FEATURE_HDPARM_HDIO_GETSET_DMA Enables the 'hdparm -d' option to get/set using_dma flag. This is dangerous stuff, so you should probably say N. +config LOCK + bool "lock" + default y + help + Small utility for using locks in scripts + config MAKEDEVS bool "makedevs" default n --- a/miscutils/Kbuild +++ b/miscutils/Kbuild @@ -20,6 +20,7 @@ lib-$(CONFIG_INOTIFYD) += inotifyd.o lib-$(CONFIG_FEATURE_LAST_SMALL)+= last.o lib-$(CONFIG_FEATURE_LAST_FANCY)+= last_fancy.o lib-$(CONFIG_LESS) += less.o +lib-$(CONFIG_LOCK) += lock.o lib-$(CONFIG_MAKEDEVS) += makedevs.o lib-$(CONFIG_MAN) += man.o lib-$(CONFIG_MICROCOM) += microcom.o --- /dev/null +++ b/miscutils/lock.c @@ -0,0 +1,132 @@ +/* + * Copyright (C) 2006 Felix Fietkau <nbd@openwrt.org> + * + * This is free software, licensed under the GNU General Public License v2. + */ +#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 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", 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; + 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; + } + } + + if (flock(fd, (shared ? LOCK_SH : LOCK_EX)) < 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; + } + } + c--; + args++; + } + + if (c != 1) + usage(argv[0]); + + file = *args; + if (unlock) + return do_unlock(); + else + return do_lock(); +}