run-one-constantly (1)

NAME

run-one - run just one instance at a time of some command and unique set of arguments (useful for cronjobs, eg)

SYNOPSIS

run-one COMMAND [ARGS]
run-this-one COMMAND [ARGS]
run-one-constantly COMMAND [ARGS]
keep-one-running COMMAND [ARGS]
run-one-until-success COMMAND [ARGS]
run-one-until-failure COMMAND [ARGS]

DESCRIPTION

run-one is a wrapper script that runs no more than one unique instance of some command with a unique set of arguments.
This is often useful with cronjobs, when you want no more than one copy running at a time.
run-this-one is exactly like run-one, except that it will use pgrep(1) and kill(1) to find and kill any running processes owned by the user and matching the target commands and arguments. Note that run-this-one will block while trying to kill matching processes, until all matching processes are dead.
run-one-constantly operates exactly like run-one except that it respawns "COMMAND [ARGS]" any time COMMAND exits (zero or non-zero).
keep-one-running is an alias for run-one-constantly.
run-one-until-success operates exactly like run-one-constantly except that it respawns "COMMAND [ARGS]" until COMMAND exits successfully (ie, exits zero).
run-one-until-failure operates exactly like run-one-constantly except that it respawns "COMMAND [ARGS]" until COMMAND exits with failure (ie, exits non-zero).

EXAMPLE

In one shell:

 $ run-one rsync -azP $HOME $USER@example.com:/srv/backup
 foouser/
 foouser/.bash_history
       40298 100%   37.13MB/s    0:00:00 (xfer#1, to-check=3509/3516)
 foouser/.viminfo
       20352 100%   98.39kB/s    0:00:00 (xfer#3, to-check=3478/3516)
 ...
 sent 746228 bytes  received 413059 bytes  36802.76 bytes/sec
 total size is 3732890955  speedup is 3219.99
In another shell, while the first is still running:

 $ run-one rsync -azP $HOME $USER@example.com:/srv/backup
 $ echo $?
 1
Another example... In one shell:

 $ run-one top
In another shell:

 $ run-one top
 $ echo $?
 1
 $ run-this-one top
 top - 17:15:36 up  1:43,  3 users,  load average: 1.05, 1.04, 1.00
 Tasks: 170 total,   1 running, 169 sleeping,   0 stopped,   0 zombie
 ...
And note that the process in the first shell was killed.
You might want to keep one ssh connection up and running all the time, with:

 $ run-one-constantly ssh -N -C -L 3128:localhost:3128 -L 7778:localhost:7778 example.com &

SEE ALSO

flock(1), kill(1), pgrep(1)

AUTHOR

This manpage and the utility was written by Dustin Kirkland <kirkland@ubuntu.com> for Ubuntu systems (but may be used by others). Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 3 published by the Free Software Foundation.
On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL, or on the web at www.gnu.org/licenses/gpl.txt.