Use extended regular expressions with grep.
Section: Searching and Pattern Matching
Extended regex search
bash
bash
grep -E 'warn|error|fatal' app.logExplanation
Equivalent to historical `egrep`; `grep -E` is preferred.
Learn the surrounding workflow
Compare similar commands or jump into common fixes when this command is part of a bigger troubleshooting path.
Related commands
Same sheet · prioritizing Searching and Pattern Matching
Search recursively under a directory
Search all matching files in a tree.
Fast recursive search with rg
Recursively search text quickly while respecting ignore rules.