How to Extract Text from Claude Code JSON Stream Output
2026-01-09 10:55 (18 hours ago)
ytyng
Background / Problem
When you use Claude Code’s --output-format=stream-json option, you get streaming output in JSON Lines format like this:
{"type":"stream_event","event":{"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"容を"}},...}
{"type":"stream_event","event":{"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"レビューして"}},...}
{"type":"stream_event","event":{"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"問"}},...}From this stream, you want to extract only the text content in the .event.delta.text field and display it in real time in the terminal.
Requirements
- Output the text fragments continuously (no newline per fragment)
- Only print a newline when
\nappears in the text - Support real-time streaming
Attempt 1: The problem with jq -r
The first method tried:
claude code ... | jq -r '.event.delta.text? // empty'Issues:
- The -r (--raw-output) option appends a newline after each output result
- Fragments like “容を”, “レビューして”, “問” end up each on their own line
- As a result, text that should be continuous gets broken up unnaturally
Solution: The jq -j option
Final solution:
claude code の ${HOME}/.claude/local/claude \
--verbose --permission-mode delegate \
--print --output-format=stream-json --include-partial-messages "/push-with-review" \
| jq -j '.event.delta.text? // empty'Characteristics of jq -j (--join-output)
- Does not automatically add newlines when printing output
- Concatenates text as-is
- Any
\ninside the text is displayed as an actual newline - Ideal for streaming processing
When you need to handle multiple message types
| jq -j '
(.event.delta.text? // empty),
(.message.content[]?.text? // empty)
'This lets you continuously output text from both stream_event and assistant messages.
jq filter details
jq features used
- Optional operator (
?) -
Using
.event.delta.text?prevents errors even if the field doesn’t exist -
Alternative operator (
//) -
// emptyoutputs nothing when the value is null or undefined -
Strict filtering with
select()(alternative)bash | jq -j 'select(.event.delta.text != null) | .event.delta.text'
Reference
jq option comparison
| Option | Behavior | Use case |
|---|---|---|
-r (--raw-output) |
Adds a newline after each result | When you want to process line by line |
-j (--join-output) |
Does not add newlines | When you want continuous text output |
-c (--compact-output) |
Compresses JSON into one line | Keep JSON structure while compacting |
Reference URLs
- jq Manual: https://jqlang.org/manual/
- JSON Lines format: https://jsonlines.org/
Conclusion
To extract only the text from Claude Code’s streaming output, jq’s -j option is the best fit.
- Simple
- Fast
- Works with real-time streaming
- No need to build a dedicated tool in Rust, etc.
Practical examples
# Basic form
claude -p "タスク内容" | jq -j '.event.delta.text? // empty'
# Filter only stream_event
claude -p "タスク内容" | jq -j 'select(.type == "stream_event") | .event.delta.text? // empty'With this, you can display Claude Code output in a human-readable format in real time.
We look forward to discussing your development needs.