Exit Codes

Horn uses exit codes to communicate validation results to scripts and CI/CD pipelines.

Code	Meaning
0	All files are compliant — no findings at or above the --fail-on threshold
1	One or more files have findings at or above the --fail-on severity
2	Runtime or CLI error (invalid arguments, unreadable files, etc.)

Usage in scripts

horn validate document.pdf --fail-on error
if [ $? -eq 0 ]; then
  echo "PDF is accessible"
elif [ $? -eq 1 ]; then
  echo "Accessibility issues found"
else
  echo "Validation error"
fi

CI/CD behavior

Most CI systems treat any non-zero exit as a failure. Use --fail-on to control when Horn triggers a pipeline failure:

# Strict: fail on any finding
horn validate ./pdfs/ --recurse --fail-on info

# Moderate: fail on warnings and errors
horn validate ./pdfs/ --recurse --fail-on warning

# Lenient: only fail on errors (default)
horn validate ./pdfs/ --recurse --fail-on error