join

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

join path/to/file1 path/to/file2

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

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

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

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