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Filter the docker ps output with a Bash alias

I’m using Docker for many of our services and the command docker ps is essential for me but I hate the long and extensive output.

For example in this server:

[root@server docker-postgres]# docker ps
CONTAINER ID   IMAGE              COMMAND                  CREATED       STATUS                 PORTS     NAMES
020ec906a5ed   bitnami/pgpool:4   "/opt/bitnami/script…"   2 weeks ago   Up 2 weeks (healthy)             pgpool
d40dd0f76e19   postgres_img       "docker-entrypoint.s…"   2 weeks ago   Up 19 hours                      postgres

The only things that I look when run docker ps are these:

pgpool        Up   2  weeks  (healthy)
postgres      Up  19  hours

I’m able to get that output running this command:

docker ps | awk -F '[[:space:]][[:space:]]+' '{print $6,$5}' | column -t --table-right 2,3,4

But that command is very large and I tried to set an alias just like this:

alias dps="docker ps | awk -F '[[:space:]][[:space:]]+' '{print $6,$5}' | column -t --table-right 2,3,4"

But running the alias I get this result:

[root@server docker-postgres]# dps
awk: cmd. line:1: {print ,}
awk: cmd. line:1:        ^ syntax error
awk: cmd. line:1: {print ,}
awk: cmd. line:1:         ^ syntax error
awk: cmd. line:1: {print ,}
awk: cmd. line:1:          ^ unexpected newline or end of string

I don’t know what is happening, I have tried changing several things in the alias line but no success…

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4

Answers


  1. Chosen as BEST ANSWER
    0

    Thanks to the suggestion of @pmf this is what I was looking for:

    alias dps="docker container ls --format 'table {{.Names}}t{{.Status}}'"

    it gives me this result:

    NAMES      STATUS
pgpool     Up 2 weeks (healthy)
postgres   Up 19 hours

  2. 0

    Don’t use an alias; use a function.

    dps () {
  docker ps | awk -F '[[:space:]][[:space:]]+' '{print $6,$5}' | column -t --table-right 2,3,4
}

    The immediate problem is that $6 and $5 were being expanded immediately at alias-definition time, because you used double-quotes for the alias definition. Nothing inside the definition of the function is subject to shell evaluation until the function is called.

    Of course, the fact that docker ls is capable of producing the output you want without having to parse the output of docker ps means you should use that instead of this pipeline.

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  3. 0

    The reason your alias is failing is the incorrect quoting. You can nominally fix it by backslash-escaping any dollar signs (or double quotes, or backticks) in the alias definition:

    alias dps="docker ps | awk -F '[[:space:]][[:space:]]+' '{print $6,$5}' | column -t --table-right 2,3,4"

    But aliases suck anyway. Use a function instead.

    dps () {
    docker ps "$@" |
    awk -F '[[:space:]][[:space:]]+' '{print $6,$5}' |
    column -t --table-right 2,3,4
}

    Of course, in this particular case, using the --format option of docker ps or docker container ls is vastly superior, like you already discovered.

    dps() {
    docker container ls --format 'table {{.Names}}t{{.Status}}' "$@"
}

    Perhaps notice also the "$@" at the end which allows you to pass in additional options or arguments.

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  4. 0

    command is very large

    This

    [[:space:]][[:space:]]+

    means 2 or more white-space characters, in GNU AWK you might express that more concisely by writing

    [[:space:]]{2,}

    See interval expression in Regexp Operators in awk for details

    See

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