How do I run this script?

Save the grep examples as search.sh, chmod +x search.sh, then run ./search.sh or use the grep commands directly in your terminal.

Does this work on macOS?

Yes. grep is pre-installed on macOS. Use grep -r instead of grep -R on older macOS versions if needed.

Search Files for Text with grep

Q: How do I search for text inside files in Linux?

Use grep -rn "pattern" /path/to/dir to search recursively with line numbers. Add --include="*.ext" to filter by file type.

Q: How do I make grep case insensitive?

Add the -i flag: grep -ri "pattern" /path/to/dir searches without case sensitivity.

What Breaks When You Search Files by Hand?

Opening files one at a time to find a config value, hardcoded credential, or error string does not scale past a dozen files. You miss matches in nested directories, skip the right file because the filename looks unrelated, and waste time scrolling logs that grep would filter in milliseconds.

grep ships pre-installed on every Linux server and macOS machine — no package manager, no IDE required. This page collects the flags that matter for daily ops: recursive search, line numbers, file-type filters, and directory exclusions that keep node_modules from flooding your results. When you need to find duplicate content consuming disk instead of text inside files, switch to the find duplicate files script.

The Script

This covers the most useful grep patterns. Paste the one you need and change the search term and path.

bash

#!/bin/bash
# Search files for text — grep reference
# Replace KEYWORD and SEARCH_DIR with your values
#
# USAGE: ./grep-search.sh
# REQUIRES: grep (pre-installed on Linux/macOS)

KEYWORD="TODO"          # ← what to search for
SEARCH_DIR="$HOME"    # ← where to search
FILE_TYPE="*.txt"     # ← file types to include

echo "Searching for '$KEYWORD' in $SEARCH_DIR..."
echo "────────────────────────────────────────"

grep -rn "$KEYWORD" "$SEARCH_DIR" \
  --include="$FILE_TYPE" \
  --color=auto

COUNT=$(grep -rc "$KEYWORD" "$SEARCH_DIR" \
  --include="$FILE_TYPE" 2>/dev/null \
  | grep -v ":0$" | wc -l)

echo "────────────────────────────────────────"
echo "Found in $COUNT file(s)"

What this does

grep -rn searches recursively (-r) through all subdirectories and shows line numbers (-n) for each match. --include filters to a specific file type. --color=auto highlights your keyword in the output so matches stand out at a glance.

Step-by-Step: The Commands You'll Use Daily

Step 1 — Search a single file

The simplest form: search one file for one term.

bash

grep "ERROR" /var/log/app.log

Every line containing "ERROR" prints to your terminal. Nothing else. Fast.

Step 2 — Add line numbers (-n)

bash

grep -n "ERROR" /var/log/app.log

# Output:
# 42: ERROR: connection refused
# 87: ERROR: disk write failed

Now you know exactly which line to jump to in your editor.

Step 3 — Search recursively across a whole folder (-r)

bash

grep -rn "TODO" ~/projects/

# Output includes filename, line number, and the matching line:
# ~/projects/api/routes.py:14:  # TODO: add auth check
# ~/projects/api/models.py:88:  # TODO: validate input

-rn is your default combination

You'll type grep -rn "keyword" /path more than almost any other command. The r searches all subdirectories, the n gives you line numbers. Memorise this one first.

Step 4 — Filter by file type (--include)

bash

# Search only .log files
grep -rn "CRITICAL" /var/log --include="*.log"

# Search only Python files
grep -rn "import os" ~/projects --include="*.py"

# Search multiple file types
grep -rn "api_key" . --include="*.py" --include="*.env"

Step 5 — Case insensitive search (-i)

bash

# Matches: error, ERROR, Error, eRrOr
grep -rni "error" /var/log --include="*.log"

grep Flags Reference

Flag	What it does	Example
-r	Recursive — search all subdirectories	grep -r "term" /folder
-n	Show line numbers in output	grep -n "term" file.txt
-i	Case insensitive match	grep -i "error" file.log
-l	Show only filenames, not the matching lines	grep -rl "TODO" ~/projects
-c	Count of matching lines per file	grep -rc "error" /var/log
-v	Invert — show lines that do NOT match	grep -v "DEBUG" app.log
-w	Match whole words only	grep -w "log" file.txt
-A 3	Show 3 lines after each match (context)	grep -A 3 "ERROR" app.log
-B 3	Show 3 lines before each match	grep -B 3 "ERROR" app.log
--include	Limit search to matching filenames	grep -r "term" . --include="*.py"
--exclude	Skip files matching pattern	grep -r "term" . --exclude="*.min.js"

Real-World Examples

Find all TODO comments across a codebase

bash

grep -rn "TODO\|FIXME\|HACK" ~/projects --include="*.py"

Scan logs for errors in the last hour

bash

# Find ERROR lines and show 2 lines of context around each
grep -n -A 2 -B 2 "ERROR" /var/log/app.log

Check if a config file contains a specific setting

bash

# Returns the line if found, nothing if not
grep "PermitRootLogin" /etc/ssh/sshd_config

Count how many files in a project contain a term

bash

# -l lists filenames only, wc -l counts them
grep -rl "api_key" . | wc -l

Search and exclude a directory (e.g. node_modules)

bash

grep -rn "password" . \
  --include="*.js" \
  --exclude-dir="node_modules" \
  --exclude-dir=".git"

Always exclude node_modules and .git

Searching a project without excluding node_modules or .git will flood your results with thousands of irrelevant matches and run significantly slower. Add --exclude-dir=node_modules --exclude-dir=.git to every recursive grep on a project folder.

Common Mistakes

Forgetting -r on a folder

Running grep "term" /var/log without -r will error with "Is a directory." You need grep -r "term" /var/log to search inside a folder recursively.

Special characters in your search term

Characters like ., *, [, and ( are regex special characters. If you're searching for them literally, either escape them with a backslash (\.) or use grep -F (fixed string mode) to treat the term as plain text, not a regex pattern.

Understanding the Commands

Command	What it does
grep "term" file	Prints every line in file containing "term"
grep -r "term" dir	Recursively searches all files in dir and subdirectories
grep -n "term" file	Adds line numbers to each matching line in output
grep -l "term" dir	Lists only filenames that contain a match — no line content
grep -c "term" file	Counts the number of matching lines in file
grep -v "term" file	Prints every line that does NOT contain "term" (invert match)
--include="*.ext"	Restricts search to files matching the glob pattern
--exclude-dir=name	Skips a directory entirely during recursive search

Frequently Asked Questions

How do I search for text inside files in Linux?

Use grep "search term" filename for a single file, or grep -rn "search term" /folder to search every file in a folder recursively. The -n flag adds line numbers so you can jump straight to each match.

How do I search multiple files with grep?

Use grep -r "term" /folder — the -r flag makes grep recurse into all subdirectories automatically. Add --include="*.py" to restrict results to a specific file type.

How do I make grep case insensitive?

Add the -i flag: grep -i "error" logfile.txt. This matches ERROR, error, Error, and any mixed-case variant.

How do I search for a word in a specific file type?

Use grep -rn "term" /folder --include="*.py". You can stack multiple --include flags to search several file types at once.

Search Files for Text with grep

What Breaks When You Search Files by Hand?

The Script

Step-by-Step: The Commands You'll Use Daily

Step 1 — Search a single file

Step 2 — Add line numbers (-n)

Step 3 — Search recursively across a whole folder (-r)

Step 4 — Filter by file type (--include)

Step 5 — Case insensitive search (-i)

grep Flags Reference

Real-World Examples

Find all TODO comments across a codebase

Scan logs for errors in the last hour

Check if a config file contains a specific setting

Count how many files in a project contain a term

Search and exclude a directory (e.g. node_modules)

Common Mistakes

Understanding the Commands

Frequently Asked Questions

How do I search for text inside files in Linux?

How do I search multiple files with grep?

How do I make grep case insensitive?

How do I search for a word in a specific file type?

The Production Bash Toolkit

Related Snippets

Frequently Asked Questions