🌱Planted April 27, 2026.
seedling 🌱
2 minutes read ⏱
If there’s a great grep use case I’m missing here, please select this sentence and use Doc Duck to tell me about it!
Pipe in output from another command
Sometimes the text I want to search is produced by another command, so I pipe it straight into grep.
ls | grep "input"Example output:
input
input-backup.txtShow all lines that contain specific text
This is the basic grep case: search a file and print only the lines that contain the text you care about.
grep "input" server.logExample output:
2026-04-27 09:14:22 validating input payload
2026-04-27 09:14:23 writing input to cache
2026-04-27 09:14:25 input processing completeShow all lines that do not contain specific text
Use -v to invert the match and show every line that does not include the text.
grep -v "input" server.logExample output:
2026-04-27 09:14:20 server starting
2026-04-27 09:14:21 loading configuration
2026-04-27 09:14:24 cache warm completeMatch text using a regular expression
Use -E for extended regular expressions when you want to match a pattern instead of fixed text. This example finds files which took at least 100ms to format.
npm run format | grep -E "[0-9]{3,}ms"Example output:
src/lib/components/component.browser.test.ts 111ms (unchanged)
src/lib/components/component.test.ts 125ms (unchanged)
src/lib/components/component.ts 286ms (unchanged)Show the preceding and following N lines for text that matches “input”
When you need surrounding context as well as the matching line, use -C N to show N lines before and after each match.
grep -C 2 "input" server.logExample output:
2026-04-27 09:14:20 server starting
2026-04-27 09:14:21 loading configuration
2026-04-27 09:14:22 validating input payload
2026-04-27 09:14:23 writing input to cache
2026-04-27 09:14:24 cache warm complete
2026-04-27 09:14:25 input processing complete
2026-04-27 09:14:26 request finished