How To Replace Text In Multiple Files Using A Bash Script In Linux

Chris
Mar 31
2 min read

If you have many files with outdated information, updating them manually is time-consuming.

Whether it's fixing outdated file paths, renaming variables, or modifying config values, Bash provides powerful tools like grep, sed, and find to automate this task.

In this post, I will show you how to replace text across multiple files efficiently using a Bash script.

Why and When Use Bash for Bulk Text Replacement?

Automating text replacement is useful for:

Updating variable names in code files
Changing file paths in scripts.
Fixing incorrect configuration settings.
Renaming project names in documentation.
Instead of editing each file manually, a Bash script can do it in seconds.

Allow me to explain it with an example Bash script.

Problem: Bulk Replace Paths in Multiple Files

Imagine you have multiple files referring to old log file paths:

Old Path: ~/data/logs/app.log

New Path: ~/data/log/app.log

Instead of searching and replacing each instance manually, let’s automate it.

Step 1: Create a Test Directory and Sample Files

First, create a test environment before modifying real files.

Create a directory in your home folder:

mkdir -p ~/replace_test && cd ~/replace_test

Create sample files containing the old path:

echo 'Log file: ~/data/logs/app.log' > script1.sh

echo 'ERROR_LOG="~/data/logs/app.log"' > config.env

echo 'echo "Processing ~/data/logs/app.log"' > process.sh

Verify occurrences of the old path:

grep "~/data/logs/app.log" *

Sample Output:

config.env:ERROR_LOG="~/data/logs/app.log"
process.sh:echo "Processing ~/data/logs/app.log"
script1.sh:Log file: ~/data/logs/app.log

Step 2: Replace Text in Multiple Files Using a Bash Script

Now, create a script named replace_text.sh:

#!/usr/bin/env bash

if [[ $# -ne 3 ]]; then
	echo "Usage: $0 <old_path> <new_path> <directory>"
	exit 1
fi

OLD_PATH=$(printf '%s\n' "$1" | sed 's/[\/&]/\\&/g')
NEW_PATH=$(printf '%s\n' "$2" | sed 's/[\/&]/\\&/g')
SEARCH_DIR=$3

echo "Replacing occurrences of: $1 -> $2 in $SEARCH_DIR"

# Find and replace text safely
find "$SEARCH_DIR" -type f -exec sed -i "s/$OLD_PATH/$NEW_PATH/g" {} +

echo "Replacement completed."

Step 3: Make the Script Executable

chmod +x replace_text.sh

Step 4: Run the Script

Execute the script to replace all occurrences of ~/data/logs/app.log with ~/data/log/app.log:

./replace_text.sh "~/data/logs/app.log" "~/data/log/app.log" ~/replace_test

Sample output:

Replacing occurrences of: ~/data/logs/app.log -> ~/data/log/app.log in /home/ostechnix/replace_test

Replacement completed.

Step 5: Verify the Changes

Run:

grep "~/data/log/app.log" *

Sample Output:

config.env:ERROR_LOG="~/data/log/app.log"
process.sh:echo "Processing ~/data/log/app.log"
script1.sh:Log file: ~/data/log/app.log

Ensure no old path remains:

grep "~/data/logs/app.log" *

If there's no output, the replacement worked.

This script:

Handles Special Characters: Escapes /, &, and other symbols correctly.
Uses find -exec sed: Safer than grep | xargs sed.
Efficient for Large Projects: Works on many files without excessive CPU usage.

You can now use this script on real files.

Precautions Before Running it on Real Files:

Backup Your Files: Always create a backup before making bulk changes
Test on a Small Sample: Run it on a test directory first, as we did with

~/replace_test

Dry Run with grep: Check how many files will be affected.
To do it, you can run

grep -rl "~/data/logs/app.log" ~/replace_test/

Manually Inspect Changes: After running the script, verify a few modified files.

Conclusion

In this tutorial, we learned how to replace text in multiple files using a simple Bash script.

We have explained how this script automates path updates in multiple files, preventing errors and saving time with a practical example. Always test with backups before running on critical files.