Expanding wildcard in echo to file

Question

Say I have the following in Bash:

FOO=/a/c*/d/
echo PATH=${FOO}:${PATH} >> .env

When I inspect the contents of the file .env the path still contains the wildcard. How can I ensure that the wildcard is expanded to the path, assuming there is only one match, so that the wildcard does not exist in the file when echoed?

Answer 1

Make it an array assignment, and then use the first element of the array (to hold with the "assuming only one match"):

foo=( /a/c*/d/ )
echo "PATH=${foo[0]}:$PATH" >>.env

By contrast, if you don't specifically want the assumption, you can use ${array[*]} after setting : as the first character in IFS to expand correctly even in the case where there were multiple matches:

foo=( /a/c*/d/ )
IFS=:
echo "PATH=${foo[*]}:$PATH" >>.env

You could avoid needing to change IFS or pay the efficiency cost of starting a subprocess by expanding the list of paths to a separate variable:

printf -v path_prefix '%s:' /a/c*/d/
echo "PATH=${path_prefix}$PATH" >>.env

Answer 2

Perhaps also

foo=( /a/c*/d/ )
echo "PATH=$(IFS=:; echo "${foo[*]}"):$PATH" >> .env

so you don't have to restore IFS