comm - compare two sorted files line by line
$ comm [options...] <file1> <file2>comm compares two sorted files specified by file1 and file2 line by line alphabetically. One of file1 and file2, but not both, can be -, in which case comm will read from the standard input for that file.
With no options, comm produces a three column output, indented by tabs, of lines unique to file1, lines unique to file2, and lines common to both files. comm provides options to suppress the output of a specific column, use case insensitive comparison or print a summary.
-1: Suppress the output of column 1 (lines unique to file1)-2: Suppress the output of column 2 (lines unique to file2)-3: Suppress the output of column 3 (lines common to file1 and file2)-i: Use case insensitive comparison of lines-c, --color: Always print colored output even if the standard output is not a tty--no-color: Do not print colored output-t, --total: Print a summaryfile1: First file to compare. (- for the standard input)file2: Second file to compare. (- for the standard input)# Files should be sorted first
$ sort < file1 > file1_sorted
$ sort < file2 > file2_sorted
# Display the default three-column output
$ comm file1_sorted file2_sorted
# Read one sorted file from the standard input
# and only display column 3
$ sort < file1 | comm -12c - file2_sorted | less
# Use case insensitive comparison,
# suppress output of all columns
# and print a summary
$ comm -123it file1_sorted file2_sorted