Let's say I want to rename all the files inside all the subfolders of a folder from foo.txt to bar.txt using zmv.
I've tried zmv '**/foo.txt' 'bar.txt' but this creates bar.txt in the root folder. How can I keep the files in their corresponding subfolder?
You need to reference the directory part in the target. You can do that by putting the wildcards in parentheses and using $1 to refer to the part matched by the parenthetical group. The ** wildcard is a little special and requires that the parentheses are around **/, no more, no less.
zmv '(**/)foo.txt' '${1}bar.txt'
You can use the -w flag to have each wildcard automatically made into a parenthetical group.
zmv -w '**/foo.txt' '${1}bar.txt'
Or you can use the -W flag and use wildcards in the replacement text — with this flag, the wildcards in the replacement text are turned into $1, $2, etc.
zmv -W '**/foo.txt' '**/bar.txt'
Alternatively, you can use $f to refer to the source path.
zmv '**/foo.txt' '$f:r.txt'