How to execute commands in docker container as part of bash shell script

Question

I would like to write a bash script that automates the following:

Get inside running container

docker exec -it CONTAINER_NAME /bin/bash

Execute some commands:

cat /dev/null > /usr/local/tomcat/logs/app.log
exit

The problematic part is when docker exec is executed. The new shell is created, but the other commands are not executed.

Is there a way to solve it?

anubhava · Accepted Answer · 2016-04-14 16:21:11Z

31

You can use heredoc with docker exec command:

docker exec -i CONTAINER_NAME bash <<'EOF'
cat /dev/null > /usr/local/tomcat/logs/app.log
exit
EOF

To use variables:

logname='/usr/local/tomcat/logs/app.log'

then use as:

docker exec -i CONTAINER_NAME bash <<EOF
cat /dev/null > "$logname"
exit
EOF

answered Apr 14, 2016 at 16:00

anubhava

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4 Comments

Thanks. This works. How can I pass parameters from outside to heredoc?

To pass parameters use EOF instead of 'EOF' at first line and then use variables inside heredoc

For those wondering, I successfully got this to work with the docker run command as well.

@ndmeiri how?? I am trying with docker run --detach-keys="ctrl-p" -it busybox and I can't make it work

user2915097 · Accepted Answer · 2016-04-15 06:15:26Z

-3

You can simply launch

docker exec -it container_id cat /dev/null > /usr/local/tomcat/logs/app.log

answered Apr 15, 2016 at 6:15

user2915097

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