Copy build artifacts from insider docker to host

Jenkins has some standard support for Docker; this is described in Using Docker with Pipeline in the Jenkins documentation. In particular, Jenkins knows how to use a Docker image that contains just tools, combined with the project's workspace directory. I'd use that support instead of trying to script docker cp.

That might look roughly like so:

pipeline {  agent none  stages {    stage('Build') {      // Jenkins will run `docker build` for you      agent { dockerfile { args '--privileged' } }      steps {        // The current working directory is bind-mounted into the container;        // the image's `ENTRYPOINT`/`CMD` is ignored.        // Copy the file out of the container:        sh "cp /usr/src/myCppProject/build/*.hex ."      }    }    stage('Program') {      agent any // so not in Docker      steps {        sh 'openocd -d0 -f board/st_nucleo_f4.cfg -c "init;targets;halt;flash write_image erase Testbench.hex;shutdown"'      }    }  }}

If you use this approach, also consider whether you should run the main build sequence via Jenkins pipeline steps, or a sh invocation that runs a shell script, or a Makefile, or if a Dockerfile is actually right. It might make sense to build a Docker image out of your customized compiler, but then use the Jenkins pipeline support to build the image for the target board rather than trying to do it all in a Dockerfile.

In the invocation you show, you can't directly docker cp a file out of an image. When you start the container, use docker run --name to give it a name, then docker cp from that container name.

sh 'docker run --name builder ... my-gcc:1.0'sh 'docker cp builder:/usr/src/myCppProject/build/*.hex .'sh 'docker rm builder'