flock: new applet

function                                             old     new   delta
flock_main                                             -     253    +253
packed_usage                                       26466   26498     +32
applet_names                                        2170    2176      +6
applet_main                                         1280    1284      +4
applet_nameofs                                       640     642      +2
applet_install_loc                                   160     161      +1
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 5/0 up/down: 298/0)             Total: 298 bytes

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

include/applets.h

@@ -161,6 +161,7 @@ IF_FLASH_ERASEALL(APPLET(flash_eraseall, _BB_DIR_USR_SBIN, _BB_SUID_DROP))
 IF_FLASH_LOCK(APPLET_ODDNAME(flash_lock, flash_lock_unlock, _BB_DIR_USR_SBIN, _BB_SUID_DROP, flash_lock))
 IF_FLASH_UNLOCK(APPLET_ODDNAME(flash_unlock, flash_lock_unlock, _BB_DIR_USR_SBIN, _BB_SUID_DROP, flash_unlock))
 IF_FLASHCP(APPLET(flashcp, _BB_DIR_USR_SBIN, _BB_SUID_DROP))
+IF_FLOCK(APPLET(flock, _BB_DIR_USR_BIN, _BB_SUID_DROP))
 IF_FOLD(APPLET(fold, _BB_DIR_USR_BIN, _BB_SUID_DROP))
 IF_FREE(APPLET(free, _BB_DIR_USR_BIN, _BB_SUID_DROP))
 IF_FREERAMDISK(APPLET(freeramdisk, _BB_DIR_SBIN, _BB_SUID_DROP))

include/usage.h

@@ -1312,6 +1312,16 @@
      "\nOptions:" \
      "\n	-v	Verbose" \
 
+#define flock_trivial_usage \
+       "[-sxun] FD|FILE [[-c] PROG ARGS]"
+#define flock_full_usage "\n\n" \
+       "[Un]lock file descriptor or file, then run PROG\n" \
+     "\nOptions:" \
+     "\n	-s	Shared lock" \
+     "\n	-x	Exclusive lock (default)" \
+     "\n	-u	Remove a lock from FD" \
+     "\n	-n	Fail rather than wait" \
+
 #define fold_trivial_usage \
        "[-bs] [-w WIDTH] [FILE]..."
 #define fold_full_usage "\n\n" \

util-linux/Config.in

@@ -191,6 +191,12 @@ config FINDFS
 	  WARNING:
 	  With all submodules selected, it will add ~8k to busybox.
 
+config FLOCK
+	bool "flock"
+	default y
+	help
+	  Manage locks from shell scripts
+
 config FREERAMDISK
 	bool "freeramdisk"
 	default n

util-linux/Kbuild

@@ -13,6 +13,7 @@ lib-$(CONFIG_FDFLUSH)           += freeramdisk.o
 lib-$(CONFIG_FDFORMAT)          += fdformat.o
 lib-$(CONFIG_FDISK)             += fdisk.o
 lib-$(CONFIG_FINDFS)            += findfs.o
+lib-$(CONFIG_FLOCK)             += flock.o
 lib-$(CONFIG_FREERAMDISK)       += freeramdisk.o
 lib-$(CONFIG_FSCK_MINIX)        += fsck_minix.o
 lib-$(CONFIG_GETOPT)            += getopt.o

util-linux/flock.c

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2010 Timo Teras <timo.teras@iki.fi>
+ *
+ * This is free software, licensed under the GNU General Public License v2.
+ */
+#include <sys/file.h>
+#include "libbb.h"
+
+int flock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int flock_main(int argc UNUSED_PARAM, char **argv)
+{
+	int mode, opt, fd;
+	enum {
+		OPT_s = (1 << 0),
+		OPT_x = (1 << 1),
+		OPT_n = (1 << 2),
+		OPT_u = (1 << 3),
+		OPT_c = (1 << 4),
+	};
+
+#if ENABLE_LONG_OPTS
+        static const char getopt_longopts[] ALIGN1 =
+		"shared\0"      No_argument       "s"
+		"exclusive\0"   No_argument       "x"
+		"unlock\0"      No_argument       "u"
+		"nonblock\0"    No_argument       "n"
+		;
+	applet_long_options = getopt_longopts;
+#endif
+	opt_complementary = "-1";
+
+	opt = getopt32(argv, "+sxnu");
+	argv += optind;
+
+	if (argv[1]) {
+		fd = open(argv[0], O_RDONLY|O_NOCTTY|O_CREAT, 0666);
+		if (fd < 0 && errno == EISDIR)
+		        fd = open(argv[0], O_RDONLY|O_NOCTTY);
+		if (fd < 0)
+			bb_perror_msg_and_die("can't open '%s'", argv[0]);
+		//TODO? close_on_exec_on(fd);
+	} else {
+		fd = xatoi_u(argv[0]);
+	}
+	argv++;
+
+	/* If it is "flock FILE -c PROG", then -c isn't caught by getopt32:
+	 * we use "+" in order to support "flock -opt FILE PROG -with-opts",
+	 * we need to remove -c by hand.
+	 * TODO: in upstream, -c 'PROG ARGS' means "run sh -c 'PROG ARGS'"
+	 */
+	if (argv[0]
+	 && argv[0][0] == '-'
+	 && (  (argv[0][1] == 'c' && !argv[0][2])
+	    || (ENABLE_LONG_OPTS && strcmp(argv[0] + 1, "-command") == 0)
+	    )
+	) {
+		argv++;
+	}
+
+	if (OPT_s == LOCK_SH && OPT_x == LOCK_EX && OPT_n == LOCK_NB && OPT_u == LOCK_UN) {
+		/* With suitably matched constants, mode setting is much simpler */
+		mode = opt & (LOCK_SH + LOCK_EX + LOCK_NB + LOCK_UN);
+		if (!(mode & ~LOCK_NB))
+			mode |= LOCK_EX;
+	} else {
+		if (opt & OPT_u)
+			mode = LOCK_UN;
+		else if (opt & OPT_s)
+			mode = LOCK_SH;
+		else
+			mode = LOCK_EX;
+		if (opt & OPT_n)
+			mode |= LOCK_NB;
+	}
+
+	if (flock(fd, mode) != 0) {
+		if (errno == EWOULDBLOCK)
+			return EXIT_FAILURE;
+		bb_perror_nomsg_and_die();
+	}
+
+	if (argv[0])
+		return spawn_and_wait(argv);
+
+	return EXIT_SUCCESS;
+}