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 <[email protected]>
---
package/utils/busybox/patches/220-add_lock_util.patch | 18 +++++++++++++++---
1 file changed, 15 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..08f489a 100644
--- a/package/utils/busybox/patches/220-add_lock_util.patch
+++ b/package/utils/busybox/patches/220-add_lock_util.patch
@@ -33,9 +33,11 @@
lib-$(CONFIG_MAKEDEVS) += makedevs.o
lib-$(CONFIG_MAN) += man.o
lib-$(CONFIG_MICROCOM) += microcom.o
+Index: busybox-1.23.2/miscutils/lock.c
+===================================================================
--- /dev/null
-+++ b/miscutils/lock.c
-@@ -0,0 +1,135 @@
++++ busybox-1.23.2/miscutils/lock.c
+@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2006 Felix Fietkau <[email protected]>
+ *
@@ -56,6 +58,7 @@
+static int unlock = 0;
+static int shared = 0;
+static int waitonly = 0;
++static int failinsteadwait = 0;
+static int fd;
+static char *file;
+
@@ -65,6 +68,7 @@
+ " -s Use shared locking\n"
+ " -u Unlock\n"
+ " -w Wait for the lock to become free, don't
acquire lock\n"
++ " -n Fail rather than wait\n"
+ "\n", name);
+ exit(1);
+}
@@ -95,6 +99,8 @@
+static int do_lock(void)
+{
+ int pid;
++ int ret;
++ int flags;
+ char pidstr[8];
+
+ if ((fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0700)) < 0) {
@@ -104,7 +110,10 @@
+ }
+ }
+
-+ if (flock(fd, (shared ? LOCK_SH : LOCK_EX)) < 0) {
++ flags = shared ? LOCK_SH : LOCK_EX;
++ flags |= failinsteadwait ? LOCK_NB : 0;
++
++ if ((ret = flock(fd, flags)) < 0) {
+ fprintf(stderr, "Can't lock %s\n", file);
+ return 1;
+ }
@@ -156,6 +165,9 @@
+ case 'u':
+ unlock = 1;
+ break;
++ case 'n':
++ failinsteadwait = 1;
++ break;
+ }
+ }
+ c--;
--
2.5.0
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