claude -p: Claude Code in scripts

So far Claude Code has worked in a dialogue: you ask, it answers, you approve. But sometimes you need Claude with nobody on the other end — in a script, on a schedule, in CI. That is what non-interactive mode is for.

One request, one run

claude -p "In one sentence: what does this repository do?"

Claude Code runs the request, prints the answer and exits: with code 0 if everything went fine, non-zero on failure. It also reads stdin, so a script can feed it, for example, a diff:

git diff | claude -p "Find obvious mistakes in this diff" --permission-mode dontAsk

An answer you can parse

With the --output-format json flag you get a single JSON object instead of text:

{"type":"result","subtype":"success","is_error":false,"num_turns":2,"result":"…","session_id":"…","permission_denials":[]}

• result — the answer itself;
• is_error — whether there was an error;
• subtype — success or the reason for an early stop, such as error_max_turns;
• num_turns — how many turns it took;
• permission_denials — which actions were denied.

Important: if the run stopped at a limit, there is no result field at all. So check the exit code and is_error first, and only then take the answer.

Always set the mode explicitly

In a script, nobody can answer a permission prompt. So the mode is passed every time: without the flag, the run takes permissions.defaultMode from your settings files — which can be auto — and with no mode set anywhere it starts in Manual, where every call that needs approval is denied.

Three flags set the limits:

• --permission-mode dontAsk — denies anything that would have needed a question in a session;
• --allowedTools — lists what is allowed after all, for example "Bash(npm test *)";
• --max-turns — caps the number of turns.

claude -p "Run the tests and tell me how many passed" \
  --output-format json --permission-mode dontAsk \
  --allowedTools "Bash(npm test *)" --max-turns 3

The space before * matters: Bash(npm test *) allows npm test with any arguments, including running it with none.