dotlockfile(1) [centos man page]
DOTLOCKFILE(1) Cistron Utilities DOTLOCKFILE(1) NAME
dotlockfile - Utility to manage lockfiles SYNOPSIS
/usr/bin/dotlockfile [-p] [-c] [-m] [-l|-u|-t] [-r retries] [lockfile] DESCRIPTION
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 dotlockfile :). OPTIONS
-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. -r retries 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 mailbox 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 actual lockfile. lockfile The lockfile to be created/removed, unless the -m option is in effect. RETURN VALUE
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 lock- file is not an error. NOTES
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 procmail, 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 mailbox, and does it safely. The above mentioned lockfile_create(3) manpage is present in the liblockfile-dev package. BUGS
None known. SEE ALSO
lockfile_create(3), maillock(3) AUTHOR
Miquel van Smoorenburg, miquels@cistron.nl 15 May 2003 DOTLOCKFILE(1)
Check Out this Related Man Page
lockfile-progs(1) Lockfile programs lockfile-progs(1) NAME
lockfile-progs - command-line programs to safely lock and unlock files and mailboxes (via liblockfile). SYNOPSIS
mail-lock [--use-pid] [--retry retry-count] mail-unlock mail-touchlock [--oneshot] lockfile-create [--use-pid] [--retry retry-count] [--lock-name] filename lockfile-remove [--lock-name] filename lockfile-touch [--oneshot] [--lock-name] filename lockfile-check [--use-pid] [--lock-name] filename DESCRIPTION
Lockfile-progs provides a set a programs that can be used 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 lockfile-create - lock a given file lockfile-remove - remove the lock on a given file lockfile-touch - touch the lock on a given file lockfile-check - check the lock on a given file By default, the filename argument refers to the name of the file to be locked, and the name of the lockfile will be filename .lock. How- ever, if the --lock-name argument is specified, then filename will be taken as the name of the lockfile itself. Each of the mail locking commands attempts to lock /var/spool/mail/<user>, where <user> is the name associated with the effective user ID, as determined by via geteuid(2). Once a file is locked, the lock must be touched at least once every five minutes or the lock will be considered stale, and subsequent lock attempts will succeed. Also see the --use-pid option and the lockfile_create(3) manpage. The lockfile-check command tests whether or not a valid lock already exists. OPTIONS
-q, --quiet Suppress any output. Success or failure will only be indicated by the exit status. -v, --verbose Enable diagnostic output. -l, --lock-name Do not append .lock to the filename. This option applies to lockfile-create, lockfile-remove, lockfile-touch, or lockfile-check. -p, --use-pid Write the current process id (PID) to the lockfile whenever a lockfile is created, and use that pid when checking a lock's validity. See the lockfile_create(3) manpage for more information. This option applies to lockfile-create, lockfile-remove, lockfile-touch, and lockfile-check. -o, --oneshot Touch the lock and exit immediately. This option applies to lockfile-touch and mail-touchlock. When not provided, these commands will run forever, touching the lock once every minute until killed. -r retry-count, --retry retry-count Try to lock filename retry-count times before giving up. Each attempt will be delayed a bit longer than the last (in 5 second incre- ments) until reaching a maximum delay of one minute between retries. If retry-count is unspecified, the default is 9 which will give up after 180 seconds (3 minutes) if all 9 lock attempts fail. 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 For lockfile-check this indicates that a valid lock exists, otherwise it just indicates successful program execution. Not 0 For lockfile-check a non-zero exit status indicates that the specified lock does not exist or is not valid. For other programs it indicates that some problem was encountered. SEE ALSO
maillock(3) touchlock(3) mailunlock(3) lockfile_create(3) lockfile_remove(3) lockfile_touch(3) lockfile_check(3) AUTHOR
Written by Rob Browning <rlb@defaultvalue.org> 0.1.12 2008-02-10 lockfile-progs(1)