How to pass arguments to Shell Script through docker run

Question

I am new to the docker world  I have to invoke a shell script that takes command line arguments through a docker container  Ex  My shell script looks like     bin bash echo  1   Dockerfile looks like this   FROM ubuntu 14 04 COPY   file sh   CMD  bin bash file sh   I am not sure how to pass the arguments while running the container

User · Answer

What I have is a script file that actually runs things. This scrip file might be relatively complicated. Let's call it "run_container". This script takes arguments from the command line:

run_container p1 p2 p3

A simple run_container might be:

#!/bin/bash
echo "argc = ${#*}"
echo "argv = ${*}"

What I want to do is, after "dockering" this I would like to be able to startup this container with the parameters on the docker command line like this:

docker run image_name p1 p2 p3

and have the run_container script be run with p1 p2 p3 as the parameters.

This is my solution:

Dockerfile:

FROM docker.io/ubuntu
ADD run_container /
ENTRYPOINT ["/bin/bash", "-c", "/run_container \"$@\"", "--"]

User · Answer

With Docker  the proper way to pass this sort of information is through environment variables    So with the same Dockerfile  change the script to     bin bash echo  FOO   After building  use the following docker command   docker run -e FOO  hello world   test

User · Answer

There are a few things interacting here    docker run your image arg1 arg2 will replace the value of CMD with arg1 arg2  That s a full replacement of the CMD  not appending more values to it  This is why you often see docker run some image  bin bash to run a bash shell in the container  When you have both an ENTRYPOINT and a CMD value defined  docker starts the container by concatenating the two and running that concatenated command  So if you define your entrypoint to be file sh  you can now run the container with additional args that will be passed as args to file sh  Entrypoints and Commands in docker have two syntaxes  a string syntax that will launch a shell  and a json syntax that will perform an exec  The shell is useful to handle things like IO redirection  chaining multiple commands together  with things like  amp  amp    variable substitution  etc  However  that shell gets in the way with signal handling  if you ve ever seen a 10 second delay to stop a container  this is often the cause  and with concatenating an entrypoint and command together  If you define your entrypoint as a string  it would run  bin sh -c  file sh   which alone is fine  But if you have a command defined as a string too  you ll see something like  bin sh -c  file sh   bin sh -c  arg1 arg2  as the command being launched inside your container  not so good  See the table here for more on how these two options interact The shell -c option only takes a single argument  Everything after that would get passed as  1   2  etc  to that single argument  but not into an embedded shell script unless you explicitly passed the args  I e   bin sh -c  file sh  1  2   arg1   arg2  would work  but  bin sh -c  file sh   arg1   arg2  would not since file sh would be called with no args    Putting that all together  the common design is   FROM ubuntu 14 04 COPY   file sh   RUN chmod 755  file sh   Note the json syntax on this next line is strict  double quotes  and any syntax   error will result in a shell being used to run the line  ENTRYPOINT   file sh     And you then run that with   docker run your image arg1 arg2   There s a fair bit more detail on this at    https   docs docker com engine reference run  cmd-default-command-or-options https   docs docker com engine reference builder  exec-form-entrypoint-example

User · Answer

Another option     To make this works  docker run -d --rm  IMG NAME  bash command1 amp  amp command2 amp  amp command3    in dockerfile  ENTRYPOINT    entrypoint sh     in entrypoint sh     bin sh  entrypoint params  1 printf     gt  entrypoint sh   s n   entry point param is  entrypoint params   PARAM1   echo  entrypoint params   cut -d    -f1    output is 1 must be  bash  it     will be tested     PARAM2   echo  entrypoint params   cut -d    -f2    the real command separated by      amp  amp   printf     gt  entrypoint sh   s n   PARAM1  PARAM1  printf     gt  entrypoint sh   s n   PARAM2  PARAM2   if     PARAM1     bash     then     printf     gt  entrypoint sh   s n   about to running  PARAM2 command      echo  PARAM2   tr   amp  amp     n    while read cmd  do          cmd     done     fi

User · Answer

If you want to run it  build time    CMD  bin bash  file sh arg1   if you want to run it  run time    ENTRYPOINT    bin bash   CMD    file sh    arg1     Then in the host shell  docker build -t test   docker run -i -t test

User · Answer

with this script in file sh     bin bash echo Your container args are         and this Dockerfile  FROM ubuntu 14 04 COPY   file sh   ENTRYPOINT    file sh     you should be able to     docker build -t test     docker run test hello world Your container args are  hello world

User · Answer

Use the same file sh    bin bash echo  1  Build the image using the existing Dockerfile  docker build -t test    Run the image with arguments abc or xyz or something else  docker run -ti --rm test  file sh abc  docker run -ti --rm test  file sh xyz

[bash] How to pass arguments to Shell Script through docker run

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