Reduce command length: Error: command too long; while reading crontab for user root

[LordMike]

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Hey,

I had a cron job that started failing, and I found out why. The error in crons logs was Error: command too long; while reading crontab for user root. Turns out cron has a length limit on commands that is 999 chars. My command is about 370 chars, but with error/stdout logging, the command in cron becomes 1.038 chars.

I'm thinking that crontabui should warn about this, refuse to write out the file, or maybe there is a way to limit the length of the command?

My command is this:

kopia snapshot create /var/lib/docker/volumes/web-nemligmbwarezdk_db/ /var/lib/docker/volumes/postgresql_pgadmin-data/ /var/lib/docker/volumes/queue_queue-data/ /var/lib/docker/volumes/homeassistant_node-red-data/ /var/lib/docker/volumes/webghmonitormbwarezdk_appdata/ && curl -fsS -m 10 --retry 5 -o /dev/null https://hc-ping.com/REDACTED;

Crontabui makes that this:

0 1 * * 0 ((({ kopia snapshot create /var/lib/docker/volumes/web-nemligmbwarezdk_db/ /var/lib/docker/volumes/postgresql_pgadmin-data/ /var/lib/docker/volumes/queue_queue-data/ /var/lib/docker/volumes/homeassistant_node-red-data/ /var/lib/docker/volumes/webghmonitormbwarezdk_appdata/ && curl -fsS -m 10 --retry 5 -o /dev/null https://hc-ping.com/REDACTED; } | tee /var/spool/cron/crontabs/32MimKQOvHpX1PwJ.stdout) 3>&1 1>&2 2>&3 | tee /var/spool/cron/crontabs/32MimKQOvHpX1PwJ.stderr) 3>&1 1>&2 2>&3); if test -f /var/spool/cron/crontabs/32MimKQOvHpX1PwJ.stderr; then date >> "/mnt/systems/crontabui/data/logs/32MimKQOvHpX1PwJ.log"; cat /var/spool/cron/crontabs/32MimKQOvHpX1PwJ.stderr >> "/mnt/systems/crontabui/data/logs/32MimKQOvHpX1PwJ.log"; fi; if test -f /var/spool/cron/crontabs/32MimKQOvHpX1PwJ.stdout; then date >> "/mnt/systems/crontabui/data/logs/32MimKQOvHpX1PwJ.stdout.log"; cat /var/spool/cron/crontabs/32MimKQOvHpX1PwJ.stdout >> "/mnt/systems/crontabui/data/logs/32MimKQOvHpX1PwJ.stdout.log"; fi

I have the following:

• I could of course move the command to a script, and run that, but I like having it all in one place :)
• I can also reduce my command by doing the below, but that's out of scope
• The following paths can be replaced with vars:
  • Your /var/spool/cron/crontabs, saves 24x6 chars (minus a var)
  • "Your" /mnt/systems/crontabui/data/logs, saves 32x4 chars (minus a var)
• Reduce the length of the unique id's.. This could simply be an incrementing number, as crontabui doesn't have a user system or a lot of jobs - in most cases I guess. If you base-64 encoded an incrementing number for each job, the first 64 jobs will all fit in a single char. stderr and stdout in the temp files can also be reduced, saving 2x 5 chars there.
• Maybe the logic can be reduced, simplifying the wrapping that needs to be done
  • I don't know how expressive cron is, but I think it could be possible to move all the logging logic into a function somehow, and call that with an id and a command.

Example command:

LOGT=/var/spool/cron/crontabs
LOGS=/mnt/systems/crontabui/data/logs
0 1 * * 0 ((({ kopia snapshot create /var/lib/docker/volumes/web-nemligmbwarezdk_db/ /var/lib/docker/volumes/postgresql_pgadmin-data/ /var/lib/docker/volumes/queue_queue-data/ /var/lib/docker/volumes/homeassistant_node-red-data/ /var/lib/docker/volumes/webghmonitormbwarezdk_appdata/ && curl -fsS -m 10 --retry 5 -o /dev/null https://hc-ping.com/REDACTED; } | tee $LOGT/32MimKQOvHpX1PwJ.stdout) 3>&1 1>&2 2>&3 | tee $LOGT/32MimKQOvHpX1PwJ.stderr) 3>&1 1>&2 2>&3); if test -f $LOGT/32MimKQOvHpX1PwJ.stderr; then date >> "$LOGS/32MimKQOvHpX1PwJ.log"; cat $LOGT/32MimKQOvHpX1PwJ.stderr >> "$LOGS/32MimKQOvHpX1PwJ.log"; fi; if test -f $LOGT/32MimKQOvHpX1PwJ.stdout; then date >> "$LOGS/32MimKQOvHpX1PwJ.stdout.log"; cat $LOGT/32MimKQOvHpX1PwJ.stdout >> "$LOGS/32MimKQOvHpX1PwJ.stdout.log"; fi

This command, where you put in the common paths, reduces the original 1.038 chars to 788 chars.

Mike.

[alseambusher]

Good idea.

[stale]

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