safe-script-execution

Safe Script Execution Fallback

When to Use This Skill

Use this pattern when execute_code_sandbox or shell_agent repeatedly fails to produce expected outputs. This manual fallback provides explicit control over script creation and execution with built-in verification.

Step-by-Step Instructions

Step 1: Verify Working Directory

Before creating any scripts, confirm your current location and permissions:

pwd
ls -la

Document the absolute path. All subsequent file operations should use explicit paths from this point.

Step 2: Create Script via Heredoc

Use shell heredoc syntax to create scripts. This avoids issues with multi-line string escaping:

cat > /full/path/to/script.py << 'HEREDOC_END'
#!/usr/bin/env python3
# Your script content here
# Single quotes around delimiter prevent variable expansion
print("Hello from script")
HEREDOC_END

Key escaping rules:

• Use single quotes around heredoc delimiter ('EOF') to prevent shell variable expansion
• If script contains the delimiter string, choose a different unique delimiter
• For bash scripts containing special characters, escape $, backticks, and !

Step 3: Make Executable and Run with Explicit Path

chmod +x /full/path/to/script.py
/full/path/to/script.py

Always use the full absolute path, never rely on . or relative paths.

Step 4: Verify Output

Confirm files were created and inspect their properties:

# Check file exists with size
ls -lh /full/path/to/output.file

# For PDFs, inspect metadata
pdfinfo /full/path/to/output.pdf 2>/dev/null || file /full/path/to/output.pdf

# For Word docs, check file type
file /full/path/to/output.docx

Step 5: Error Handling

If execution fails:

1. Check script syntax: python3 -m py_compile /path/to/script.py
2. Check permissions: ls -l /path/to/script.py
3. Check available disk space: df -h .
4. Review stderr output carefully

Example: PDF Generation Fallback

# Step 1: Verify directory
pwd
ls -la

# Step 2: Create Python script
cat > /workspace/generate_pdf.py << 'SCRIPT_END'
from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas

c = canvas.Canvas("/workspace/output.pdf", pagesize=letter)
c.drawString(100, 750, "Generated PDF")
c.save()
SCRIPT_END

# Step 3: Execute
chmod +x /workspace/generate_pdf.py
python3 /workspace/generate_pdf.py

# Step 4: Verify
ls -lh /workspace/output.pdf
pdfinfo /workspace/output.pdf 2>/dev/null || echo "PDF created, pdfinfo unavailable"

Anti-Patterns to Avoid

• ❌ Don't use relative paths like ./script.py - always use absolute paths
• ❌ Don't rely on unquoted heredoc delimiters if script contains variables
• ❌ Don't skip verification steps - always confirm output exists and has expected size
• ❌ Don't assume working directory - always pwd first

Troubleshooting Checklist

• [ ] Working directory confirmed with pwd
• [ ] Script file exists after heredoc creation (ls -l)
• [ ] Script has execute permissions (chmod +x)
• [ ] Output file exists with non-zero size (ls -lh)
• [ ] File type verified (file command or type-specific inspection)