lock -n is similiar to flock -n. If the lock was already taken,
fail with exit code = 1 and write error message to stderr.
example:
if ! lock -n /tmp/foo ; then
echo lock exits.
else
echo lock was free. But is locked now.
fi
> lock was free. But is locked now.
> lock exists.
Signed-off-by: Alexander Couzens <lyn...@fe80.eu>
---
v1: implement feature
v2: rename variable failinsteadwait into try_lock
extend description of -n
run make package/utils/busybox/refresh
v3: drop changelog from commit message
remove ret variable
package/utils/busybox/patches/220-add_lock_util.patch | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/package/utils/busybox/patches/220-add_lock_util.patch
b/package/utils/busybox/patches/220-add_lock_util.patch
index f42edcb..9cac9e6 100644
--- a/package/utils/busybox/patches/220-add_lock_util.patch
+++ b/package/utils/busybox/patches/220-add_lock_util.patch
@@ -1,6 +1,6 @@
--- a/include/applets.src.h
+++ b/include/applets.src.h
-@@ -211,6 +211,7 @@ IF_LN(APPLET_NOEXEC(ln, ln, BB_DIR_BIN,
+@@ -211,6 +211,7 @@ IF_LN(APPLET_NOEXEC(ln, ln, BB_DIR_BIN,
IF_LOAD_POLICY(APPLET(load_policy, BB_DIR_USR_SBIN, BB_SUID_DROP))
IF_LOADFONT(APPLET(loadfont, BB_DIR_USR_SBIN, BB_SUID_DROP))
IF_LOADKMAP(APPLET(loadkmap, BB_DIR_SBIN, BB_SUID_DROP))
@@ -35,7 +35,7 @@
lib-$(CONFIG_MICROCOM) += microcom.o
--- /dev/null
+++ b/miscutils/lock.c
-@@ -0,0 +1,135 @@
+@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2006 Felix Fietkau <n...@openwrt.org>
+ *
@@ -56,6 +56,7 @@
+static int unlock = 0;
+static int shared = 0;
+static int waitonly = 0;
++static int try_lock = 0;
+static int fd;
+static char *file;
+
@@ -65,6 +66,7 @@
+ " -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);
+}
@@ -95,6 +97,7 @@
+static int do_lock(void)
+{
+ int pid;
++ int flags;
+ char pidstr[8];
+
+ if ((fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0700)) < 0) {
@@ -104,7 +107,10 @@
+ }
+ }
+
-+ if (flock(fd, (shared ? LOCK_SH : LOCK_EX)) < 0) {
++ 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;
+ }
@@ -156,6 +162,9 @@
+ case 'u':
+ unlock = 1;
+ break;
++ case 'n':
++ try_lock = 1;
++ break;
+ }
+ }
+ c--;
--
2.5.0
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