comm

Select or reject lines common to two files. Both files must be sorted. More information: https://www.gnu.org/software/coreutils/manual/html_node/comm-invocation.html.

• Produce three tab-separated columns: lines only in first file, lines only in second file and common lines:

comm file1 file2

• Print only lines common to both files:

comm -12 file1 file2

• Print only lines common to both files, reading one file from stdin:

cat file1 | comm -12 - file2

• Get lines only found in first file, saving the result to a third file:

comm -23 file1 file2 > file1_only

• Print lines only found in second file, when the files aren't sorted:

comm -13 <(sort file1) <(sort file2)