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>

5 files changed, 105 insertions, 0 deletions

diff --git a/include/applets.h b/include/applets.h
index 2d784bd84..83c1792ac 100644
--- a/include/applets.h
+++ b/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))
diff --git a/include/usage.h b/include/usage.h
index f4259a11d..0aea010c7 100644
--- a/include/usage.h
+++ b/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" \
diff --git a/util-linux/Config.in b/util-linux/Config.in
index f04511bb1..d0d8df339 100644
--- a/util-linux/Config.in
+++ b/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
diff --git a/util-linux/Kbuild b/util-linux/Kbuild
index 72a2ef1cd..99e3efea3 100644
--- a/util-linux/Kbuild
+++ b/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
diff --git a/util-linux/flock.c b/util-linux/flock.c
new file mode 100644
index 000000000..78b1e4ba3
--- /dev/null
+++ b/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;
+}