Documentation

Tries to perform some task if it can obtain the lock, Otherwise, just gives up without doing the task

withTemp safely creates an empty file (not open for writing) and returns its name.

The temp file operations are rather similar to the locking operations, in that they both should always try to clean up, so exitWith causes trouble.

withOpenTemp creates a temporary file, and opens it. Both of them run their argument and then delete the file. Also, both of them (to my knowledge) are not susceptible to race conditions on the temporary file (as long as you never delete the temporary file; that would reintroduce a race condition).

withTempDir creates a temporary directory, runs the action and then removes the directory. The location of that directory is determined by the contents of _darcsprefstmpdir, if it exists, otherwise by $DARCS_TMPDIR, and if that doesn't exist then whatever your operating system considers to be a a temporary directory (e.g. $TMPDIR under Unix, $TEMP under Windows).

If none of those exist it creates the temporary directory in the current directory, unless the current directory is under a _darcs directory, in which case the temporary directory in the parent of the highest _darcs directory to avoid accidentally corrupting darcs's internals. This should not fail, but if it does indeed fail, we go ahead and use the current directory anyway. If $DARCS_KEEP_TMPDIR variable is set temporary directory is not removed, this can be useful for debugging.

withPermDir is like withTempDir, except that it doesn't delete the directory afterwards.

Do an action in a newly created directory of the given name. If the directory is successfully created but the action raises an exception, the directory and all its content is deleted. Caught exceptions are re-thrown.