DOTLOCKFILE(1) Cistron Utilities DOTLOCKFILE(1)
dotlockfile - Utility to manage lockfiles
/usr/bin/dotlockfile [-p] [-c] [-m] [-l|-u|-t] [-r retries] [lockfile]
Dotlockfile is a command line utility to safely create, test and remove
lockfiles. Lockfiles are created in an NFS-safe way. Dotlockfile can
can also be used to lock and unlock mailboxes even if the mailspool
directory is only writable by group mail.
The name dotlockfile comes from the way mailboxes are locked for
updates on a lot of UNIX systems. A lockfile is created with the same
filename as the mailbox but with the string ".lock" appended.
The names dotlock and lockfile were already taken - hence the name dot-
-l Create a lockfile. This is the default.
-u Remove a lockfile.
-c Check for the existence of a valid lockfile.
-t Touch an existing lockfile (update the timestamp).
-p Write the process-id of the calling process into the lockfile.
Also when testing for an existing lockfile, check the contents
for a process-id to find out if the lockfile is still valid.
The number of times dotlockfile retries to acquire the lock if
it failed the first time before giving up. The initial sleep
after failing to acquire the lock is 5 seconds. After each next
try, a sleep of 5 seconds extra occurs up to a maximum sleep of
60 seconds between tries. The default number of retries is 5.
-m Lock or unlock the current users mailbox. The path to the mail-
box is the default system mailspool directory (usually
/var/mail) with the username as gotten from getpwuid() appended.
If the environment variable $MAIL is set, that is used instead.
Then the string ".lock" is appended to get the name of the
The lockfile to be created/removed, unless the -m option is in
Zero on success, and non-zero on failure. For the -c option, sucess
means that a valid lockfile is already present. When locking (the
default, or the -l option) dotlockfile returns the same values as the
library function lockfile_create(3). Unlocking a non-existant lockfile
is not an error.
The lockfile is created exactly as named on the command line. The
extension .lock is not automatically added.
This utility is a lot like the lockfile(1) utility included with proc-
mail, and the mutt_dotlock(1) utility included with mutt. However the
command-line arguments differ, and so does the return status. It is
believed that dotlockfile is the most flexible implementation, since it
automatically detects when it needs to use priviliges to lock a mail-
box, and does it safely.
The above mentioned lockfile_create(3) manpage is present in the
Miquel van Smoorenburg, miquelsATcistron.nl
15 May 2003 DOTLOCKFILE(1)