Claude/Code/How To/Use Essential Commands

• How To Use Essential Claude Code Commands

  • Goal

    • Quickly apply six Claude Code commands that automate tests, reuse docs, save tokens, deepen reasoning, and extend context access in any project.

  • Preconditions

    • Claude Code ≥ v1.0 installed and in PATH
    • MCP server linked to GitHub
    • Project open in Cursor or terminal with git initialized

  • Procedure

    • 1. Set Up Project Rules with claude.md

      • Run /init and confirm creation of claude.md.
      • Edit the file with rules such as:

        1. Write secure, best-practice Python code

        2. Generate & run tests for each function; iterate until tests pass

        3. Delete test scripts after success

        4. Commit after every new function

      • Commit claude.md to the repo so Claude Code enforces the rules automatically.

    • 2. Add Custom User Commands

      • Create claude-commands/claude-docs.md (or any .md) containing reference snippets.
      • Invoke it anywhere: /user claude-docs "Give me a Claude API example". Claude Code injects the file’s content for instant answers.

    • 3. Run One-Shot File-Scoped Queries with -p

      • Pipe a single file to Claude Code to cut token usage:
        bash

        cat src/utils.py | claude -p "What does the sanitize_input function do?"

      • Claude focuses only on the piped file, answers, then exits.

    • 4. Extract Context from Images

      • Drag-and-drop a screenshot (e.g., code from docs) into chat.
      • Prompt: “Extract the text” → Claude performs OCR; follow up with coding questions using the extracted text.

    • 5. Control Output & Encourage Deep Reasoning

      • Structured output:
        bash

        claude -p "List 10 currency pairs with rates" --output-format json

      • Extended thinking: prepend your query with "Think deeply about …" to trigger longer, more rigorous analysis.

    • 6. Access Additional Working Directories with --add-dir

      • Add additional working directories for Claude to access (validates each path exists as a directory):
        bash

        claude --add-dir ../apps ../lib

      • Useful for monorepos or when working with related projects that need to be accessible in the same session
      • Reference: CLI flags documentation

  • Troubleshooting

    • Command not found → confirm claude --version returns correctly.
    • Rules ignored → ensure claude.md is at project root and committed.
    • Token overrun → use -p or split context into smaller files.
    • Image OCR failed → use clear PNG/JPG < 5 MB and retry drag-drop.

  • References

    • Claude Code Official Documentation
    • Project Rules with claude.md