[SOLVED] Echo dynamic sed to file inside Dockerfile

Issue

I am working on a Dockerfile, inside of which I want to dynamically create a sed expression based on the input argument variable, and write this expression to a file.

Here's part of the Dockerfile:

FROM ubuntu
ARG VERSION

RUN echo $VERSION > /usr/local/testfile

RUN echo '#!/bin/sh \n\
sed -i "s/\"version\"/\${VERSION}/g" file' > /usr/local/foo.sh

the image builds fine. When I start a container from that image, and inspect the files:

# cat /usr/local/testfile
0.0.1

# cat /usr/local/foo.sh
#!/bin/sh
sed -i "s/\"version\"/\${VERSION}/g" file

I notice that the $VERSION was not replaced correctly in the sed command. What am I missing here? I've tried a few different things (e.g. "$VERSION") but none of them worked.

Solution

I ended up breaking down the command. I created a variable for the sed command by using string concatenation and then I echoed that to the file separately:

FROM ubuntu
ARG VERSION

ENV command="sed -i s/\"version\"/""$VERSION""/g"

RUN echo '#!/bin/sh' > /usr/local/foo.sh
RUN echo $command >> usr/local/foo.sh

# cat /usr/local/foo.sh
#!/bin/sh
sed -i s/"version"/0.0.1/g

Answered By - Paolo

Answer Checked By - Katrina (WPSolving Volunteer)