The repeat command

repeat is a dirt simple Python script to repeat a command indefinitely, or for a fixed number of iterations. I wrote it because I got bored of writing (for example):

$ for ($i = 1; $i -le 100; $i++) { echo "Run $i"; do_stuff; echo "Run $i complete" }

repeatedly in PowerShell, while trying to provoke threading-related race conditions in test code. What I wanted to write instead was something like:

$ repeat 100 do_stuff

to repeat 100 times, or even just:

$ repeat do_stuff

to repeat indefinitely. repeat lets me do that. It also lets me use the same command regardless of environment, freeing me from having to remember whether I'm in GNU Bash, PowerShell, or a regular Windows CMD prompt.

Example usage:

$ repeat 3 python -c "print 2+2"
repeat: Repeating ['python', '-c', 'print 2+2'] 3 times.
repeat: Starting run 1 of 3.
4
repeat: Run 1 of 3 completed.
repeat: Starting run 2 of 3.
4
repeat: Run 2 of 3 completed.
repeat: Starting run 3 of 3.
4
repeat: Run 3 of 3 completed.
repeat: Exiting with return code 0.

The script will stop as soon as the command being executed exits with a nonzero return code, and will itself exit with that same return code. On successful completion it will exit with return code 0. To keep going even if some of the iterations of the command fail, use the -k option:

$ repeat -k 3 python -c "import sys; sys.exit(1)"
repeat: Repeating ['python', '-c', 'import sys; sys.exit(1)'] 3 times.
repeat: Starting run 1 of 3.
repeat: Run 1 of 3 failed with return code 1.
repeat: # of successes: 0, # of failures: 1 (100.00%).
repeat: Starting run 2 of 3.
repeat: Run 2 of 3 failed with return code 1.
repeat: # of successes: 0, # of failures: 2 (100.00%).
repeat: Starting run 3 of 3.
repeat: Run 3 of 3 failed with return code 1.
repeat: # of successes: 0, # of failures: 3 (100.00%).
repeat: Exiting with return code 1.

More simply, omit the count argument to repeat indefinitely:

$ repeat python -c "print 2+2"
repeat: Repeating ['python', '-c', 'print 2+2'] forever.
repeat: Starting run 1.
4
repeat: Run 1 completed.
repeat: Starting run 2.
4
repeat: Run 2 completed.
repeat: Starting run 3.
4
repeat: Run 3 completed.
repeat: Starting run 4.
4
repeat: Run 4 completed.
repeat: Starting run 5.
<and so on>

You can also explicitly request indefinite repetitions with a count of forever. In the unlikely case that your command starts with an integer, you'll need to use forever to avoid the beginning of the command being interpreted as a count:

$ repeat forever 999 ...

This of course also means that in the equally unlikely event that your command happens to start with forever, you'll also need to use forever:

$ repeat forever forever ....

To silence the progress output, use the -q option:

$ repeat -q 3 python -c "print 2+2"
4
4
4

Usage

Type repeat --help to see options:

$ repeat --help
usage: repeat [-h] [-q] count ...

Repeat a command forever or a fixed number of times.

positional arguments:
  count        number of iterations, or 'forever'
  cmd          command to execute

optional arguments:
  -h, --help        show this help message and exit
  -q, --quiet       suppress progress output
  -k, --keep-going  keep running even if some iterations fail

Installation

Clone this repository, enter the top-level directory, and do a "python setup.py install" (or "python setup.py develop" if you prefer):

git clone git@github.com:mdickinson/repeat.git repeat
cd repeat
python setup.py develop

repeat runs on Python 2 (version 2.6 or later) and on Python 3 (version 3.2 or later). It depends on the six package. For Python 2.6, it also depends on the PyPI version of argparse.

License

The repeat script is copyright (c) 2014 Mark Dickinson.

repeat is licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.