Performing a sed -i on a list of files in stdin
ack, bash, django-1.5, django-urls, sed
Solution
ack -l "{% url" | xargs sed -i "s/{% url \([A-Za-z0-9_]*\) /{% url '\1' /g"
`-l` lists matching files from `ack` (a simpler version of your `cut`/`uniq`). `xargs` performs the operation on each argument acquired from the pipe (i.e. each file). What you were trying to do would be `sed` on the actual string of the list of files from stdin which of course can't be updated in place.
Problem
So I recently upgraded Django from 1.4 to 1.5. I found out I need to update all my template codes to add single quotes like from ``` {% url user_detail pk=user.pk %} ``` to ``` {% url 'user_detail' pk=user.pk %} ``` I'm kind of new to bash commands like `sed`, but I approached my issue in 2 parts. The 1st part was to get a list of all the files that needs updating. I did that with ``` ack "{% url" | cut -d ":" -f1 | uniq ``` this will give me an ouput like ``` templates/some_file.html templates/admin/another_file.html ``` The 2nd part was playing around with sed ``` cat templates/some_file.html | sed "s/{% url \([A-Za-z0-9_]*\) /{% url '\1' /g" ``` Both of those commands work fine. Now the question is how do I combine those two commands so that `sed` will add single-quotes around the url name in every file found by `ack`? If I try ``` ack "{% url" | cut -d ":" -f1 | uniq | sed -i "s/{% url \([A-Za-z0-9_]*\) /{% url '\1' /g" ``` it gives me the error ``` sed: -i may not be used with stdin ``` EDIT I'm running OS X (BSD variant) so I needed to use `sed -i "" "s/{% url \([A-Za-z0-9_]*\) /{% url '\1' /g"`.