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How to Search for Text Within Files in Linux Using grep? (Regex Examples)
How to Search for Text Within Files in Linux Using grep? (Regex Examples)
Use grep with flags like -i (case-insensitive), -n (line numbers), -r (recursive), -w (whole word), -E (extended regex), -o (only matching part), -v (invert), and -c (count) to efficiently search text in files without GUI tools.
Use grep with the right flags and patterns to find text inside files—no need for editors or GUI tools.
Basic text search in a single file
Run grep "search_term" filename to print all matching lines. By default, it’s case-sensitive and shows only the lines—not filenames or line numbers.
- Add
-ito ignore case:grep -i "error" app.log - Use
-nto show line numbers:grep -n "404" access.log - Use
-Hto always show filename (helpful even with one file):grep -H "timeout" config.conf
Search across multiple files and directories
Pass multiple filenames or use wildcards like *.log. To search recursively in subdirectories, add -r (or -R):
-
grep -r "DEBUG" /var/log/— scans all files under/var/log/ -
grep -r --include="*.py" "import requests" ./src/— only Python files -
grep -r --exclude-dir="node_modules" "fetch(" ./— skip specific directories
Simple regex patterns for real-world use
Enable extended regex with -E (or use egrep). No need for backslashes before , ?, or |.
- Match whole words only:
grep -w "cat" animals.txt— avoids matching “scatter” - Find lines starting with “#”:
grep "^#" script.sh - Find lines ending in “.js”:
grep "\.js$" files.txt— escape dot, anchor end - Match IP-like patterns:
grep -E "([0-9]{1,3}\.){3}[0-9]{1,3}" network.log
Filter and refine results
Combine grep with other tools or use built-in options to narrow output.
- Show only matching parts (not full lines):
grep -o "user=[^[:space:]]*" auth.log - Invert match (show non-matching lines):
grep -v "^$" file.txt— skip blank lines - Count matches instead of printing lines:
grep -c "failed" syslog - Highlight matches in color:
grep --color=always "ERROR" *.log | less -R
Basically just combine flags and patterns based on what you’re after—no complex setup needed. Regex gets more powerful with practice, but even basic ^, $, ., and * cover most daily tasks.
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