Bash Script to Batch Rename Files Easily

Use a Bash loop like for file in *.txt; do mv "$file" "newprefix_$file"; done to batch rename files by adding a prefix.

Examples

InputFiles: report1.txt, report2.txt

OutputRenamed to: newprefix_report1.txt, newprefix_report2.txt

InputFiles: image1.jpg, image2.jpg

OutputRenamed to: photo_image1.jpg, photo_image2.jpg

InputFiles: fileA, fileB (no extension)

OutputRenamed to: renamed_fileA, renamed_fileB

How to Think About It

To batch rename files, think about looping over all files matching a pattern, then for each file, create a new name by adding or changing parts like prefixes or extensions, and finally rename the file using the mv command.

Algorithm

1

Get the list of files matching a pattern.

2

For each file, create a new name by modifying the original name.

3

Rename the file to the new name using the move command.

4

Repeat until all files are processed.

Code

bash

for file in *.txt; do
  newname="newprefix_$file"
  echo "Renaming '$file' to '$newname'"
  mv "$file" "$newname"
done

Output

Renaming 'report1.txt' to 'newprefix_report1.txt'
Renaming 'report2.txt' to 'newprefix_report2.txt'

Dry Run

Let's trace renaming 'report1.txt' and 'report2.txt' by adding 'newprefix_'

1

List files

Files found: report1.txt, report2.txt

2

First file rename

Original: report1.txt, New: newprefix_report1.txt

3

Second file rename

Original: report2.txt, New: newprefix_report2.txt

Original Filename	New Filename
report1.txt	newprefix_report1.txt
report2.txt	newprefix_report2.txt

Why This Works

Step 1: Loop over files

The for loop goes through each file matching the pattern like *.txt.

Step 2: Create new name

We build a new filename by adding a prefix to the original filename.

Step 3: Rename file

The mv command renames the file from the old name to the new name.

Alternative Approaches

Using rename command

bash

rename 's/^/newprefix_/' *.txt

This is simpler but depends on the availability and version of the rename tool on your system.

Using find with exec

bash

find . -maxdepth 1 -name '*.txt' -exec bash -c 'mv "$0" "newprefix_$0"' {} \;

Useful for more complex directory structures but more complex syntax.

Complexity: O(n) time, O(1) space

Time Complexity

The script processes each file once in a loop, so time grows linearly with the number of files.

Space Complexity

The script uses constant extra space, renaming files in place without storing large data.

Which Approach is Fastest?

The simple Bash loop and the rename command both run in O(n) time; rename is often faster but less flexible.

Approach	Time	Space	Best For
Bash loop with mv	O(n)	O(1)	Simple, flexible renaming
rename command	O(n)	O(1)	Quick renaming with regex
find with exec	O(n)	O(1)	Complex directory structures