This includes both a bash function and Python class that implements exclusive locking via a filesystem file.
This is used to prevent multiple instances of a script from running at the same time.
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Uses trap to remove a lockfile on exit of script. This is one big advantage over using "lockfile(1)" within the script.
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Writes PID to lockfile and detects if locked process has exited.
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Provides atomic semantics via "ln"/os.link().
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Unit tests.
Copy the "bashlock" function into your code and then call it with a lockfile name, exit on failure:
Bash:
bashlock /var/run/${0##*/}.pid || exit 1
# [Remainder of script code here]or using an environment variable:
BASHLOCKFILE=/var/run/${0##*/}.pid
bashlock || exit 1
# [Remainder of script code here]Python:
from bashlock import Bashlock
if not Bashlock('/tmp/locktest').acquire():
print('Unable to obtain lock')
sys.exit(1)
# [Remainder of code here]Done!
To run the tests:
bash tests/bashtest
python3 -m pytest tests/*.pyThe following exit codes are used:
* 0: Lock successfully obtained
* 1: Lock is held by another process
* 2: Usage error
* 3: Failed to write temporary lockfile
Author: Sean Reifschneider [email protected]
Date: Wed Sep 18, 2013
License: 2-Clause BSD
Code/Bugs: https://github.com/realgo/bashlock