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    <p>A wee bit beyond the scope of your question... but here's what I do.</p> <p>The "how do I test a cron job?" question is closely connected to "how do I test scripts that run in non-interactive contexts launched by other programs?" In cron, the trigger is some time condition, but lots of other *nix facilities launch scripts or script fragments in non-interactive ways, and often the conditions in which those scripts run contain something unexpected and cause breakage until the bugs are sorted out.</p> <p>A general approach to this problem is helpful to have.</p> <p>One of my favorite techniques is to use a script I wrote called '<a href="https://github.com/Stabledog/crontest" rel="noreferrer">crontest</a>'. It launches the target command inside a GNU screen session from within cron, so that you can attach with a separate terminal to see what's going on, interact with the script, even use a debugger.</p> <p>To set this up, you would use "all stars" in your crontab entry, and specify crontest as the first command on the command line, e.g.:</p> <pre><code>* * * * * crontest /command/to/be/tested --param1 --param2 </code></pre> <p>So now cron will run your command every minute, but crontest will ensure that only one instance runs at a time. If the command takes time to run, you can do a "screen -x" to attach and watch it run. If the command is a script, you can put a "read" command at the top to make it stop and wait for the screen attachment to complete (hit enter after attaching)</p> <p>If your command is a bash script, you can do this instead:</p> <pre><code>* * * * * crontest --bashdb /command/to/be/tested --param1 --param2 </code></pre> <p>Now, if you attach with "screen -x", you'll be facing an interactive bashdb session, and you can step through the code, examine variables, etc.</p> <pre><code>#!/bin/bash # crontest # See https://github.com/Stabledog/crontest for canonical source. # Test wrapper for cron tasks. The suggested use is: # # 1. When adding your cron job, use all 5 stars to make it run every minute # 2. Wrap the command in crontest # # # Example: # # $ crontab -e # * * * * * /usr/local/bin/crontest $HOME/bin/my-new-script --myparams # # Now, cron will run your job every minute, but crontest will only allow one # instance to run at a time. # # crontest always wraps the command in "screen -d -m" if possible, so you can # use "screen -x" to attach and interact with the job. # # If --bashdb is used, the command line will be passed to bashdb. Thus you # can attach with "screen -x" and debug the remaining command in context. # # NOTES: # - crontest can be used in other contexts, it doesn't have to be a cron job. # Any place where commands are invoked without an interactive terminal and # may need to be debugged. # # - crontest writes its own stuff to /tmp/crontest.log # # - If GNU screen isn't available, neither is --bashdb # crontestLog=/tmp/crontest.log lockfile=$(if [[ -d /var/lock ]]; then echo /var/lock/crontest.lock; else echo /tmp/crontest.lock; fi ) useBashdb=false useScreen=$( if which screen &amp;&gt;/dev/null; then echo true; else echo false; fi ) innerArgs="$@" screenBin=$(which screen 2&gt;/dev/null) function errExit { echo "[-err-] $@" | tee -a $crontestLog &gt;&amp;2 } function log { echo "[-stat-] $@" &gt;&gt; $crontestLog } function parseArgs { while [[ ! -z $1 ]]; do case $1 in --bashdb) if ! $useScreen; then errExit "--bashdb invalid in crontest because GNU screen not installed" fi if ! which bashdb &amp;&gt;/dev/null; then errExit "--bashdb invalid in crontest: no bashdb on the PATH" fi useBashdb=true ;; --) shift innerArgs="$@" return 0 ;; *) innerArgs="$@" return 0 ;; esac shift done } if [[ -z $sourceMe ]]; then # Lock the lockfile (no, we do not wish to follow the standard # advice of wrapping this in a subshell!) exec 9&gt;$lockfile flock -n 9 || exit 1 # Zap any old log data: [[ -f $crontestLog ]] &amp;&amp; rm -f $crontestLog parseArgs "$@" log "crontest starting at $(date)" log "Raw command line: $@" log "Inner args: $@" log "screenBin: $screenBin" log "useBashdb: $( if $useBashdb; then echo YES; else echo no; fi )" log "useScreen: $( if $useScreen; then echo YES; else echo no; fi )" # Were building a command line. cmdline="" # If screen is available, put the task inside a pseudo-terminal # owned by screen. That allows the developer to do a "screen -x" to # interact with the running command: if $useScreen; then cmdline="$screenBin -D -m " fi # If bashdb is installed and --bashdb is specified on the command line, # pass the command to bashdb. This allows the developer to do a "screen -x" to # interactively debug a bash shell script: if $useBashdb; then cmdline="$cmdline $(which bashdb) " fi # Finally, append the target command and params: cmdline="$cmdline $innerArgs" log "cmdline: $cmdline" # And run the whole schlock: $cmdline res=$? log "Command result: $res" echo "[-result-] $(if [[ $res -eq 0 ]]; then echo ok; else echo fail; fi)" &gt;&gt; $crontestLog # Release the lock: 9&lt;&amp;- fi </code></pre>
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