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Wrapper launching single process using its execution permission as concurrency semaphore
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| #!/bin/sh | |
| if [ -z "$1" ]; then | |
| echo "Usage: $0 <command> [args...]" | |
| exit | |
| fi | |
| trap ':' SIGINT SIGTERM | |
| chmod u-x "$0" | |
| "$@" | |
| status=$? | |
| chmod u+x "$0" | |
| exit $status |
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Protect cron from launching new jobs until the previous one has finished:
Even though the job is scheduled to run every 10 min, it will be executed every 20 min, because it takes 15 min (900 sec) to complete and every other launch attempt will fail with the
Permission deniederror protecting from undesirable concurrency.Note: Every job needs its own copy of
only.shas the script's execution permission bit is used as a semaphore; symlink won't work.