Replacing new lines with nulls in bash

If you have a list of file names separated by new lines, and you want to turn it into a list of file names separated by null characters, for instance for use as input to xargs, then you can use the tr command, like this:

  $ cat /path/to/new-lines | tr '\n' '\0' > /path/to/null-separated

I found a whole article on various ways to replace text on *nix: rmnl — remove new line characters with tr, awk, perl, sed or c/c++.


I learned about the ‘tr’ Unix command today. It’s for translating text in streams. The particular example was:

  echo | tr '012' '001'

And I didn’t really understand what that did, but now I do. Basically the ‘echo’ part will echo a new line character, which is octal 012. Then tr will read its input stream and read that new line. It then has a rule to translate 012 (new line) to 001 (Ctrl+A), which it does. So basically it’s just a way of getting a Ctrl+A character in a stream. If you use Ctrl+A as your regular expression delimiter you’re unlikely to have a collision in the expression itself.