CODEWITHSUNDEEP
bash
Vincent Teyssier
Vincent Teyssier

Reputation: 2217

Bash script runs but no output on main commands and not executed

I'm setting a cron job that is a bash script containing the below:

#!/bin/bash
NUM_CONTAINERS=$(docker ps -q | wc -l)
if [ $NUM_CONTAINERS -lt 40 ]
then
  echo "Time: $(date). Restart containers." 
  cd /opt 
  pwd
  sudo docker kill $(docker ps -q)
  docker-compose up -d
  echo "Completed." 
else
  echo Nothing to do
fi

The output is appended to a log file:

>> cron.log

However the output in the cron file only shows:

Time: Sun Aug 15 10:50:01 UTC 2021. Restart containers. 
/opt
Completed.

Both command do not seem to execute as I don't see any change in my containers either. These 2 non working commands work well in a standalone .sh script without condition though. What am I doing wrong?

User running the cron has sudo privileges, and we can see the second echo printing.

Upvotes: 0

Views: 915

Answers (1)

paxdiablo
paxdiablo

Reputation: 881153

Lots of times, things that work outside of cron don't work within cron because the environment is not set up in the same way.

You should generally capture standard output and error, to see if something going wrong.

For example, use >> cron.log 2>&1 in your crontab file, this will capture both.

There's at least the possibility that docker is not in your path or, even if it is, the docker commands are not working for some other reason (that you're not seeing since you only capture standard output).

Capturing standard error should help out with that, if it is indeed the issue.

As an aside, I tend to use full path names inside cron scripts, or set up very limited environments at the start to ensure everything works correctly (once I've established why it's not working correctly).

Upvotes: 2

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