[SOLVED] How to detect if the current script is running in a docker build?

Issue

Suppose I have a Dockerfile which runs a script,

RUN ./myscript.sh

How could I write the myscript.sh so that it could detect if itself is launched by the RUN command during a docker build?

#! /bin/bash

# myscript.sh

if <What should I do here?>
then
  echo "I am in a docker build"
else
  echo "I am not in a docker build"
fi

Ideally, it should not require any changes in the Dockerfile, so that the caller of myscript.sh does not need specialized knowledge about myscript.sh.

Solution

Try this :

#!/bin/bash

# myscript.sh

isDocker(){
    local cgroup=/proc/1/cgroup
    test -f $cgroup && [[ "$(<$cgroup)" = *:cpuset:/docker/* ]]
}

isDockerBuildkit(){
    local cgroup=/proc/1/cgroup
    test -f $cgroup && [[ "$(<$cgroup)" = *:cpuset:/docker/buildkit/* ]]
}

isDockerContainer(){
    [ -e ./dockerenv ]
}

if isDockerBuildkit || (isDocker && ! isDockerContainer)
then
  echo "I am in a docker build"
else
  echo "I am not in a docker build"
fi

Answered By - Philippe

Answer Checked By - Marie Seifert (WPSolving Admin)