diff Command - Compare Files Line by Line

The diff command is used to compare files line by line. It outputs the differences between two files or directories, making it useful for code review, patch creation, and file comparison.

Syntax

diff [options] file1 file2

Examples

diff file1.txt file2.txt

diff -u old.c new.c

diff -r dir1 dir2

Notes

• Use -u for unified diff format, commonly used in patches.
• Can be combined with grep to filter diff output.
• For applying differences, use the patch command (if available).