Mandatory file locking in Mac OS X

Question

According to a man pages the following approaches supports only advisory locking: flock , lockf and fcntl . Is there any way to mandatory lock a some file by a single process, for example with a write lock, so that other process will not able to open this file with the write permissions?

Answer 1

No. Operating systems in the Unix family do not generally support mandatory file locking ¹ . This includes Linux, BSD, and OS X.

On some Unixes, you are prevented from opening files for writing if they are executable images that are currently running; open() will fail with ETXTBSY . However, you can always just unlink (delete) the file and create a new one instead, and nothing will prevent that.

Footnotes

¹ : This is not entirely true, but mandatory file locks require a bit of work, mandatory locks are platform-specific, and OS X has no support for them.