lockfile-progs
NAME
lockfile-progs - command-line programs to safely lock and unlock
files and mailboxes (via liblockfile).
SYNOPSIS
mail-lock
[
--retry
R retry-count
]
mail-unlock
mail-touchlock
[
--oneshot ]
lockfile-create
[
--retry
R retry-count
]
R filename
lockfile-remove
R filename
lockfile-touch
[
--oneshot ]
R filename
DESCRIPTION
lockfile-progs
provide a method to lock and unlock mailboxes and files safely (via
liblockfile).
mail-lock:
lock the current user's mailbox.
mail-unlock:
unlock the current user's mailbox.
mail-touchlock:
touch the lock on the current user's mailbox.
Each of the mail locking commands is applied to the file
/var/spool/mail/<user>, if possible, where <user> is the name of the
current user (determined from the effective uid via geteuid(2)).
lockfile-create:
lock a given file.
lockfile-remove:
remove the lock on a given file.
lockfile-touch:
touch the lock on a given file.
Once a file is locked, the lock must be touched at least once every
five minutes, or it will be considered stale and a subsequent attempt
to lock the file will succeed. For both of the locking commands
(mail-touchlock
and
lockfile-touch),
the --oneshot argument causes the program to touch the lock and exit
immediately. Otherwise the program will loop forever, touching the
lock once every minute until it is killed.
For both of the locking commands
(mail-lock
and
lockfile-create),
the --retry argument specifies (as an integer) the maximum number of
times to retry locking the file before giving up if attempts are
failing. Each retry will be delayed a little longer than the last (in
5 second increments) until a maximum delay of one minute between
retries is reached. The default retry count is 9 which, if all 9
attempts to lock the file fail, will give up after 180 seconds (3
minutes). Note that the description above matches the one for the
underlying lockfile_create(3) call, but in fact, this option might be
better named --tries since --retry 0 will not try to lock at all.
EXAMPLES
Locking a file during a lengthy process:
lockfile-create /some/file
lockfile-touch /some/file &
# Save the PID of the lockfile-touch process
BADGER="$!"
do-something-important-with /some/file
kill "${BADGER}"
lockfile-remove /some/file
EXIT STATUS
0
Successful program execution.
NOT-0
Some problem was encountered.
SEE ALSO
HISTORY
1998 - Written by Rob Browning <rlb@defaultvalue.org>.