bash regular expressions to get docker container port number

Question

So I'm trying to get a specific port number from my docker cluster, this is done because I need the port later on.

When I do docker-compose ps I get the following output

contaimer_db_1            docker-entrypoint.sh mysqld      Up      3306/tcp
container_node_1          /usr/bin/supervisord -n          Up      0.0.0.0:3902->3902/tcp
container_php_1           docker-php-entrypoint php-fpm    Up      9000/tcp
container_redis_1         docker-entrypoint.sh redis ...   Up      6379/tcp

What I would like to get is the port number just from the container_node_1 3902

So far I got

docker-compose ps | grep "[ :]\?[[:digit:]]\{4\}"

But this will get all ports since they have 4 numbers in a row. How would I change this to make sure it will only get the node port?

If it's any help, the node container will always show up as 0.0.0.0:1234->1234

Answer 1

Using Awk alone and calling split() function twice,

docker-compose ps | awk '$1=="container_node_1"{n=split($NF,arr1,"->"); split(arr1[n],arr2,"/"); print arr2[1]}'

will give you the port number as intended. This will work on any POSIX compliant Awk installed.

If you have GNU Awk installed, you can use its gensub() function to do the regex match and extract the port number,

docker-compose ps | awk '$1=="container_node_1"{print gensub(/.*->([[:digit:]]+)\/(.+)$/,"\\1","g",$NF)}'

RegEx Demo for the regex used inside.

Answer 2

I would rather use docker inspect

example

docker-compose ps

Name Command State Ports

dockerpartkeepr_database_1 docker-entrypoint.sh mysqld Up 3306/tcp
dockerpartkeepr_partkeepr_1 docker-php-entrypoint apac ... Up 0.0.0.0:80->80/tcp

So I will try to get the port linked to 80

docker inspect --format '{{ (index (index .NetworkSettings.Ports "80/tcp") 0).HostPort }}' dockerpartkeepr_partkeepr_1

which will show

80

see my answer How to get ENV variable when doing Docker Inspect

for more explanations