Can I alias a subcommand? (shortening the output of `docker ps`)

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Nathaniel Waisbrot

The docker command has a ps sub-command that emits very long lines:

$ docker ps -a
CONTAINER ID        IMAGE                             COMMAND                  CREATED             STATUS                      PORTS                                                                                                                                                                                                                                                                                                        NAMES
6e8ec8a16da4        waisbrot/wait:latest              "/wait"                  4 minutes ago       Exited (0) 4 minutes ago                                                                                                                                                                                                                                                                                                                 wait-for-janus-test
9dbf0739561f        whoop/downsampler:master          "./run.bash"             4 minutes ago       Up 4 minutes                0.0.0.0:32855->4369/tcp, 0.0.0.0:32854->9100/tcp, 0.0.0.0:32853->9101/tcp, 0.0.0.0:32852->9102/tcp, 0.0.0.0:32851->9103/tcp, 0.0.0.0:32850->9104/tcp, 0.0.0.0:32849->9105/tcp, 0.0.0.0:32848->9106/tcp, 0.0.0.0:32847->9107/tcp, 0.0.0.0:32846->9108/tcp, 0.0.0.0:32845->9109/tcp, 0.0.0.0:32844->9110/tcp   metrics-downsampler-test
6cf56623bb48        whoop/janus:master                "./start.bash"           4 minutes ago       Up 4 minutes                0.0.0.0:32843->80/tcp                                                                                                                                                                                                                                                                                        janus-test
882b50303d54        whoop/recalculator:master         "./run.bash"             4 minutes ago       Exited (1) 4 minutes ago                                                                                                                                                                                                                                                                                                                 internum-test

It can be instructed to output only specific columns:

docker ps --format "table {{.Image}}\t{{.Names}}\t{{.Ports}}\t{{.Status}}"

I'd like to be able to say docker ps and get the --format "table..." argument added on for me. Is there a nice way to do this?

I know I could say

alias dp='docker ps --format ...'

but I'd prefer to keep the sub-command.

I'm using zsh as my shell.

Using Docker Config

Since this is fundamentally a docker questions, not a bash question, you don't even need an alias. Docker CLI allows you to customize these commands in your own config file! From this great tip from Container 42:

  1. Create or find your docker config file (if you've ever used docker login it should already be created.

    ~/.docker/config.json

  2. Then add the default formatting for docker to use every time it runs the ps command as a top level property in the config:

    {
    "psFormat": "table {{.Image}}\t{{.Names}}\t{{.Ports}}\t{{.Status}}",
}

  3. Then just run docker ps like normal:

    docker ps

PS Format

Docker uses go templates and has a list of the valid placeholders:

| Command | Description | | ----------------- | ------------------------------------------------- | | .ID | Container ID | | .Image | Image ID | | .Command | Quoted command | | .CreatedAt | Time when the container was created. | | .RunningFor | Elapsed time since the container was started. | | .Ports | Exposed ports. | | .Status | Container status. | | .Size | Container disk size. | | .Names | Container names. | | .Labels | All labels assigned to the container. | | .Label | Value of a specific label for this container. | | .Mounts | Names of the volumes mounted in this container. | | .Networks | Names of the networks attached to this container. |

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