Question

I was trying to rename all files using find but after i ran this…

find . -name '*tablet*' -exec sh -c "new=$(echo {} | sed 's/tablet/mobile/') && mv {} $new" \;

i found that my files where gone, changed it to echo the value of $new and found that it always kept the name of the first file so it basically renamed all files to have the same name

$ find . -name '*tablet*' -exec sh -c "new=$(echo {} | sed 's/tablet/mobile/') && echo $new" \;
_prev_page.tablet.erb
_prev_page.tablet.erb
_prev_page.tablet.erb
_prev_page.tablet.erb
_prev_page.tablet.erb
_prev_page.tablet.erb
_prev_page.tablet.erb

also tried to change to export new=..., same result

Why doesn’t the value of new change?

Answer 1

The problem I believe is that the command substitution is expanded by bash once then find uses the result in each invocation. I could be wrong with the reason.

When I have similar stuff before I write out a shell script eg

#! /bin/bash
old="$1"
new="${1/tablet/mobile}"
if [[ "${old}" != "${new}" ]]; then
    mv "${old}" "${new}"
fi

that takes care of renaming the file then I can call that script from the find command

find . -name "*tablet*" -exec /path/to/script '{}' \;

makes things much simpler to sort out.

EDIT:

HAHA after some messing around with the quoting you can sort this out by changing the double quotes to single quotes encapsulating the command. As is the $() is expanded by the shell command. if done as below the command substitution is done by the shell invoked by the exec.

find . -name "*tablet*" -exec sh -c 'new=$( echo {} | sed "s/tablet/mobile/" ) && mv {} $new' \;

SO the issue is to do with when the command substitution is expanded, by puting it in single quotes we force the expansion in each invokation of sh.