snaeil/makeWrapper_and_wrapProgram.md

## makeWrapper_and_wrapProgram.md

      
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              makeWrapper_and_wrapProgram.md
            
          
    makeWrapper and wrapProgram

Nix generally assumes run-time dependencies is a subset of the build-time dependencies.
This means many Nix builder functions try to automatically scan the output for runtime dependencies and "rewrite" them for runtime usage.
However shell scripts which are often exported by packages do not get this automatic scanning treatment.
This means you have to use the makeWrapper package and use either the makeWrapper or wrapProgram utility functions.
You may use them in the postFixup phase of a derivation:
postFixup = ''
  wrapProgram $out/bin/some-script \
    --set PATH ${lib.makeBinPath [
      coreutils
      findutils
      gnumake
      gnused
      gnugrep
    ]}
'';

We use the lib.makeBinPath to compose paths from a number of derivation outputs.
One should always try to use --set instead of --prefix because you shouldn't rely on the user profile environment variables.