stdout

The channel on which a program writes its ordinary result. When you run a command, it’s what you see in the terminal. In hooks, what the hook writes here is read by Claude Code (at session start, for example, it reaches Claude).

How it appears in the course

For finer control, the hook can write a JSON answer on stdout (“standard output”, where a program writes its normal result). For example, "decision": "block" with a "reason" (the reason for blocking). Or additionalContext, to give Claude extra information.
What does a hook receive, and what does it answer? · Module 07, Hooks: automatic actions
Everything this hook writes on stdout goes straight into the information that Claude sees.
Ready-to-use recipes · Module 07, Hooks: automatic actions

Where you learn it

In module 07 · Hooks: automatic actions, in the Claude Code for Beginners course.

Related terms

Exit codeFormatterHookjqLockfilestderr

Learn Claude Code from zero, in plain English

12 modules with 1–2 minute lessons, which you can also do on your phone. The first two modules are free.

Start with the first lessonAll terms