Compare files line by line

Default Output

diff file1.txt file2.txt

Change	Description
r1ar2	Append the lines at the position r2 in second file
	to the position r1 in the first file.
r1cr2	Change the lines at position r1 with the lines
	at the position r2 in the second file.
r1dr2	Delete the lines in the first file at position r1, which
	would have appeared at range r2 in the second file.

diff Change Commands

Context Format

diff -c file1.txt file2.txt

Indicator	Meaning
blank	A line shown for context. Doesn't indicate a difference.
-	A line deleted. Appears in first file, but not in second.
+	A line added. Apperas in second file but not in first.
!	A line changed. Both versions will be displayed.

diff Context Format Change Indicators

Unified Format

diff -u file1.txt file2.txt

Indicator	Meaning
blank	The line is shared by both files
-	The line was removed from first file
+	The line was added to the first file

diff Unified Format Change Indicators

Preparing diff for use with patch

diff -Naur old_file new_file > diff_file r option supports recursion of directory tree