Command `docker` can not work with pipeline. Do not work with `|`, `>`, `>>`

Question

I want to search some text output by command docker, but it seems not work with pipeline.

My expected result of docker > a should write all output in the terminal to file a. And expected result of docker | grep info should print something that contains info Display system-wide information.

I added myself to the group docker. The following is test cases.

lala@ubu:~/projects/docker 14:19:42
$ grep docker /etc/group
docker:x:999:lala
lala@ubu:~/projects/docker 14:19:47
$ ls -al 
总用量 8
drwxr-xr-x  2 lala lala 4096 1月  10 14:15 .
drwxr-xr-x 10 lala lala 4096 1月  10 10:21 ..
lala@ubu:~/projects/docker 14:19:57
$ ls -al | grep x
drwxr-xr-x  2 lala lala 4096 1月  10 14:15 .
drwxr-xr-x 10 lala lala 4096 1月  10 10:21 ..
lala@ubu:~/projects/docker 14:20:01
$ docker

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:

...... unnecessary output

Run 'docker COMMAND --help' for more information on a command.
lala@ubu:~/projects/docker 14:20:03
$ docker | grep x

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:

...... the same as above. unnecessary output

Run 'docker COMMAND --help' for more information on a command.
lala@ubu:~/projects/docker 14:20:15
$ docker > a

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:

...... the same as above again. unnecessary output

Run 'docker COMMAND --help' for more information on a command.
lala@ubu:~/projects/docker 14:21:26
$ cat a
lala@ubu:~/projects/docker 14:21:28
$ file a
a: empty
lala@ubu:~/projects/docker 14:21:30
$

docker >> a did not work, either.

I want to read the specific command help, such as `docker | grep info` to see how to use `docker info` — tteng little, Jan 10 '20 at 06:43
You may need to edit your post to define what you want to do and possibly what did you expect as result — PhoenixBlue, Jan 10 '20 at 06:52

LinPy · Accepted Answer · 2020-01-10T06:54:42.230

that is because , docker command need some arguments that is it returing errors, you can use this:

docker 2>&1| grep info

output:

 -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
  -v, --version            Print version information and quit
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  version     Show the Docker version information
Run 'docker COMMAND --help' for more information on a command.

anyway the correct way is just to type:

docker info --help

output:

Usage:  docker info [OPTIONS]

Display system-wide information

Options:
  -f, --format string   Format the output using the given Go template

got it. I have not encountered such situation and do not know what to google. Thanks! — tteng little, Jan 10 '20 at 06:49

Command `docker` can not work with pipeline. Do not work with `|`, `>`, `>>`

1 Answers1