Exit codes

Code	Meaning
0	Projects changed and/or are affected. Output files were written.
166	Nothing changed and nothing is affected. No output files were written.
other	An error occurred. The message is printed to stderr.

Nothing changed: 166

When the diff produces no changed projects and no affected projects, the tool prints No affected projects where found for the current changes and exits with 166. Since no affected.proj is written, running dotnet build affected.proj afterwards would fail on a missing file — so guard it:

dotnet affected # ...other args
if [ "$?" -eq 0 ]; then
    dotnet build affected.proj
fi

Caution

166 means nothing changed, which is not the same as nothing is affected. If projects changed but no other project depends on them, the exit code is 0 — those changed projects still need to be built.

GitHub Actions

With the dotnet-affected action, the same idea is expressed as a step condition:

- name: Install dependencies
  if: success() && steps.affected.outputs.affected != ''
  run: dotnet restore affected.proj