lm (Line-Mismatch), compares two files and outputs unique lines from each file to stdout, identifying lines that appear in one file but not the other.

Here, a file called fileA.txt contains a list of items. fileB.txt contains another list, some items overlapping with fileA.txt and some unique. lm is used to display the unique lines from both files.

▶ cat fileA.txt
Apple
Banana
Orange

▶ cat fileB.txt
Banana
Orange
Grape
Mango

▶ lm fileA.txt fileB.txt
L1: fileA.txt: Apple
L4: fileB.txt: Grape
L5: fileB.txt: Mango

▶ cat fileA.txt
Apple
Banana
Orange

▶ cat fileB.txt
Banana
Orange
Grape
Mango

Note that lm only outputs unique lines to stdout. You can redirect the output to a file for further use:

▶ lm fileA.txt fileB.txt > unique-lines.txt
▶ cat unique-lines.txt
L1: fileA.txt: Apple
L4: fileB.txt: Grape
L5: fileB.txt: Mango

(None currently implemented.)

You can install using Go:

go install -v github.com/armamini/lm@latest

Or download the source code and run it directly:

go run script.go <file1> <file2>