Assign results of globbing to a variable in Bash

Question

My colleague, Ryan, came to me with a bug in his Bash script, and I identified the problem with this test:

$ mkdir ryan $ mkdir ryan/smells-bad $ FOO=ryan/smells-* $ echo $FOO ryan/smells-bad $ touch $FOO/rotten_eggs touch: cannot touch `ryan/smells-*/rotten_eggs': No such file or directory 

From this I infer that the globbing happens during the echo command, not when the variable FOO is created.

We have a couple of workarounds, in descending order of ungracefulness:

touch `echo $FOO`/rotten_eggs 

Or:

pushd cd $FOO touch rotten_eggs popd 

But neither is satisfying. Am I missing a trick?

Answer 1

The problem is that the glob will only expand if the file "rotten_eggs" exists, because it is included in the glob pattern. You should use an array.

FOO=( ryan/smells-* ) touch "${FOO[@]/%//rotten_eggs}" 

The FOO array contains everything matched by the glob. The expansion using % appends /rotten_eggs to each element.

Answer 2

Consider

for dir in $FOO; do     touch "$dir/rotten_eggs" done 

Note that this will touch multiple files if the glob pattern matches more than one pathname.