flock(2) is documented as “blocking if an incompatible lock is held by another process” and with “locks created by flock() are associated with an open file table entry”, so it should be expected that flock-ed locks by several threads of the same process don’t interact. (the flock documentation doesn’t mention threads). Hence, the solution should … Read more
Sorry if I reply to a dead question: After locking the file, open another copy of it, fstat both copies and check the inode number, like this: lockfile = “/tmp/some_name.lock”; while(1) { fd = open(lockfile, O_CREAT); flock(fd, LOCK_EX); fstat(fd, &st0); stat(lockfile, &st1); if(st0.st_ino == st1.st_ino) break; close(fd); } do_something(); unlink(lockfile); flock(fd, LOCK_UN); This prevents the … Read more
To lock the file: exec 3>filename # open a file handle; this part will always succeed flock -x 3 # lock the file handle; this part will block To release the lock: exec 3>&- # close the file handle You can also do it the way the flock man page describes: { flock -x 3 … Read more
Advisory locking has been used for ages and it can be used in bash scripts. I prefer simple flock (from util-linux[-ng]) over lockfile (from procmail). And always remember about a trap on exit (sigspec == EXIT or 0, trapping specific signals is superfluous) in those scripts. In 2009 I released my lockable script boilerplate (originally … Read more