join

Join lines of two sorted files on a common field. More information: https://www.gnu.org/software/coreutils/manual/html_node/join-invocation.html.

• Join two files on the first (default) field:

join path/to/file1 path/to/file2

• Join two files using a comma (instead of a space) as the field separator:

join -t ',' path/to/file1 path/to/file2

• Join field3 of file1 with field1 of file2:

join -1 3 -2 1 path/to/file1 path/to/file2

• Produce a line for each unpairable line for file1:

join -a 1 path/to/file1 path/to/file2

• Join a file from stdin:

cat path/to/file1 | join - path/to/file2