locking files

[Christopher Lee]

>>>>> "Christopher" == Christopher Lee <clee at gnwy100.wuh.wustl.edu> writes:

    >> chmod g+s tmp; chmod g-x tmp python
    >>> import fcntl, FCNTL fp = open("tmp", "rw") fd = fp.fileno()
    >>> fcntl.lockf(fd, FCNTL.F_LOCK) # secures the lock, prevents

Oops, FCNTL.F_LOCK is wrong here (although when I typed it in the example
worked by coincidence).  Looking at the python source of fcntlmodule.c,
it's actually asking for fcntl's LOCK_EX, LOCK_SH, LOCK_UN, or LOCK_NB.

-chris


#ifndef LOCK_SH
#define LOCK_SH		1	/* shared lock */
#define LOCK_EX		2	/* exclusive lock */
#define LOCK_NB		4	/* don't block when locking */
#define LOCK_UN		8	/* unlock */