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run−one

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 AT example DOT 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 AT example DOT 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 AT ubuntu DOT 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 http://www.gnu.org/licenses/gpl.txt.

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