TIL - How to Escape Single Quotes in Nix Indented Strings

Recently I was moving my pi sessions to XDG directories and hit an issue putting a Bash script inside a Nix indented string. The script used read -r -d '' to read file paths separated by a null character.

The Bash was valid, but the '' ended the surrounding Nix string, so this didn’t parse:

pkgs.writeShellScript "list-files" ''
  while IFS= read -r -d '' file; do
    printf '%s\n' "$file"
  done < <(find . -type f -print0)
''

To fix this, add another single quote ¹:

pkgs.writeShellScript "list-files" ''
  while IFS= read -r -d ''' file; do
    printf '%s\n' "$file"
  done < <(find . -type f -print0)
''

The ''' in the Nix string becomes '' in the generated Bash script. So the empty quotes are preserved without ending the Nix string.

That’s it!