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--help and help are successful commands so output should not go to error. QE teams have requested this change, also users doing docker help | less or docker run --help | less would expect this to work. Usage statement should only be printed when the user asks for it. Errors should print error message and then suggest the docker COMMAND --help command to see usage information. The current behaviour causes the user to have to search for the error message and sometimes scrolls right off the screen. For example a error on a "docker run" command is very difficult to diagnose. Finally erros should always exit with a non 0 exit code, if the user makes a CLI error. Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan) Upstream-commit: 61b129d81802e3c988cc0e67e488b24968dd748a Component: engine
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% DOCKER(1) Docker User Manuals % Docker Community % JUNE 2014
NAME
docker-attach - Attach to a running container
SYNOPSIS
docker attach [--help]/ [--no-stdin[=false]] [--sig-proxy[=true]] CONTAINER
DESCRIPTION
If you docker run a container in detached mode (-d), you can reattach to the detached container with docker attach using the container's ID or name.
You can detach from the container again (and leave it running) with CTRL-p CTRL-q (for a quiet exit), or CTRL-c which will send a SIGKILL to the
container, or CTRL-\ to get a stacktrace of the Docker client when it quits.
When you detach from a container the exit code will be returned to
the client.
OPTIONS
--help Print usage statement
--no-stdin=true|false Do not attach STDIN. The default is false.
--sig-proxy=true|false Proxy all received signals to the process (even in non-TTY mode). SIGCHLD, SIGKILL, and SIGSTOP are not proxied. The default is true.
EXAMPLES
Attaching to a container
In this example the top command is run inside a container, from an image called fedora, in detached mode. The ID from the container is passed into the docker attach command:
# ID=$(sudo docker run -d fedora /usr/bin/top -b)
# sudo docker attach $ID
top - 02:05:52 up 3:05, 0 users, load average: 0.01, 0.02, 0.05
Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.1%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 373572k total, 355560k used, 18012k free, 27872k buffers
Swap: 786428k total, 0k used, 786428k free, 221740k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 17200 1116 912 R 0 0.3 0:00.03 top
top - 02:05:55 up 3:05, 0 users, load average: 0.01, 0.02, 0.05
Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 373572k total, 355244k used, 18328k free, 27872k buffers
Swap: 786428k total, 0k used, 786428k free, 221776k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 17208 1144 932 R 0 0.3 0:00.03 top
HISTORY
April 2014, Originally compiled by William Henry (whenry at redhat dot com) based on docker.com source material and internal work. June 2014, updated by Sven Dowideit SvenDowideit@home.org.au