How to copy a newest file from Docker container to local machine-CodePudding

How can I copy the newest file in docker directory to local directory? I know that I can use docker cp but I have to know what file I have to copy. I can figure it out inside docker container by sorting the files at taking the last one but I don't know how to extract this path outside the container so that I could use docker cp.

CodePudding user response：

Let's create a Docker image with 5 files with different timestamps

FROM debian
WORKDIR /app
RUN echo a > ahsgdfkjhagsdkf && sleep 1 && \
    echo b > hsagdkfjhasgdkf && sleep 1 && \
    echo c > ahsdgfkhjasgdfk && sleep 1 && \
    echo d > hasgdfkjhasgdkh && sleep 1 && \
    echo e > kasdflkjhasldfk
CMD ["tail", "-f", "/dev/null"]

Build and run it with

docker build -t test .
docker run -d --name mytest test

Then we can use ls -t | head -1 to find the newest file. Combine that with tar to compress it in the container, send it to stdout and then decompress it on the host, like this

docker exec mytest /bin/sh -c 'tar -czO $(ls -t | head -1)' | tar -zxf -

The newest file, kasdflkjhasldfk, has now been copied to the host.

We need to execute /bin/sh in the container and pass it the command in quotes. If we didn't have it in quotes, $(ls -t | head -1) would be evaluated on the host and we would pass a filename to tar that exists on the host, but not in the container.

By having the command that should be run in the container in quotes, $(ls -t | head -1) is evaluated in the container and we get the correct filename.