if xx or xx, else... condition in dockerfile - dockerfile

Question

I would need to provide an if or..., else condition inside a dockerfile.
I found a solution for an if, else... But I am not able to include an or condition inside the if
This solution works:
RUN if [ condition 1 ] ; then \
command 1; \
else; then \
condition 2; fi
I have tried something like this, unsuccessfully:
RUN if [ condition 1 | condition 2 ] ; then \
command 1; \
else; then \
condition 2; fi
How can I add the or inside the conditional?

Answer 1

Within a single Docker RUN instruction, you're running a shell command, and any Bourne shell syntax is allowed. If you're using [ ... ] that's actually running test(1) which has a -o operator for "or".
RUN if [ condition1 -o condition 2 ]; then \
command1; \
else \
command2; \
fi
The POSIX spec suggests the -o option is obsolete, and recommends using the shell || operator instead.
RUN if [ condition1 ] || [ condition2 ]; then ...; fi
RUN if test condition1 || test condition2 ; then ...; fi
More generally, Dockerfiles don't support conditionals; you can't conditionally COPY a file in, for example. Conversely, if you are writing complex installation logic, you can write and test an ordinary shell script on the host, COPY it into the image, and RUN it, which can be easier than trying to remember to backslash-escape every line ending.