· shell-scripting-2

Sed across multiple files

Pankhuri and I needed to rename a method and change all the places where it was used and decided to see if we could work out how to do it using sed.

We needed to change a method call roughly like this:


home_link(current_user)

To instead read:


homepage_path

For which we need the following sed expression:


sed -i 's/home_link([^)]*)/homepage_path/' [file_name]

Which works pretty well if you know which file you want to change but we wanted to run it over the whole code base.

A bit of googling led us to this thread on devshed which suggested we’d need to get a list of the files and then run sed through the list:


for file in `find .  -type f`; do sed -i 's/home_link([^)]*)/homepage_path/' $file; done

That pretty much works but it doesn’t play nicely if the file has a space in the name since sed thinks the file name has ended before it actually has.

I was pretty sure that we should be able to pipe the output of the find into xargs and a bit more googling led us to the following solution:


find . -type f -print0 | xargs -0 sed -i 's/home_link([^)]*)/homepage_path/'

The ‘print0’ flag is described like so:


This primary always evaluates to true.  It prints the pathname of the current file to standard output, followed by an ASCII NUL character (character code 0).

While ‘-0’ in ‘xargs’ is described like this:


  -0      Change xargs to expect NUL (``\0'') characters as separators, instead of spaces and newlines.  This is expected to be used in concert with the -print0 function in find(1).

It also runs amazingly fast!

If anyone knows a better way feel free to point it out in the comments.

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