Question

In one of my bash scripts I have this variable, containing a list of directories to be excluded from tar, plus their parent directory to be processed:

EXLIST="\
 --exclude='/data/sub1/*' \
 --exclude='/data/sub2/*' \
 --exclude='/data/sub3/*' \
 /data \
 "

echo ${EXLIST} | /usr/bin/xargs -0 tar -cf _data.tar

However, tar cowardly refuses to create an empty archive because what it really receives after substituting ${EXLIST} is:

echo --exclude='/data/sub1/*' | /usr/bin/xargs -0 tar -cf /home/_data.tar

Which tells me that newlines are getting in the way?

I could of course define EXLIST as one long line but I prefer not to, as this makes the list less readable.

Is there a way, in bash, to “flatten” the lines to a string, so that tar can process it?

Answer 1

You should use an array in this case, without xargs.

EXLIST=("--exclude='/data/sub1/*'" \
        "--exclude='/data/sub2/*'" \
        "--exclude='/data/sub3/*'" \
        "/data")

tar -cf _data.tar "${EXLIST[@]}"

Using this method, each element of the array is a separate argument for tar.