Claude Code CLI Reference Manual

I. CLI Commands

II. CLI Flags

The following flags customize Claude Code runtime behavior:

Note：--output-format jsonFlags are ideal for scripting and automation; you can programmatically parse Claude response output.

III. Extended Notes

3.1 Agent Flag Format

--agentsThe flag accepts a JSON object to define one or more custom subagents. Each subagent requires a unique name as the key, and the value is an object containing the following fields:

Example

claude --agents '{
  "code-reviewer": {
    "description": "Expert code reviewer. Use proactively after code changes.",
    "prompt": "You are a senior code reviewer. Focus on code quality, security, and best practices.",
    "tools": ["Read", "Grep", "Glob", "Bash"],
    "model": "sonnet"
  },
  "debugger": {
    "description": "Debugging specialist for errors and test failures.",
    "prompt": "You are an expert debugger. Analyze errors, identify root causes, and provide fixes."
  }
}'

System Prompt Flag

Claude Code provides 3 ways to customize the system prompt to meet different usage needs:

Usage scenarios and examples

1. --system-prompt: Completely take over the system prompt and clear default instructions

   claude --system-prompt "You are a Python expert who only writes type-annotated code"

2. --system-prompt-file: Read prompt from file, suitable for standardized scenarios

   claude -p --system-prompt-file ./prompts/code-review.txt "Review this PR"

3. --append-system-prompt: Keep default functionality, append custom requirements (recommended for most scenarios)

   claude --append-system-prompt "Always use TypeScript and include JSDoc comments"

Note：--system-promptand--system-prompt-fileMutually exclusive, cannot be used at the same time.
Tip: Prioritize using--append-system-prompt, as it preserves Claude Code's built-in capabilities while meeting customization needs; only use the other two flags when full customization is required.

Print mode (-p) detailed usage (output format, streaming, programmatic integration, etc.), refer toSDK documentation。