join

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

• Join two files on the first (default) field:
  join {{file1}} {{file2}}
• Join two files using a comma (instead of a space) as the field separator:
  join -t {{','}} {{file1}} {{file2}}
• Join field3 of file1 with field1 of file2:
  join -1 {{3}} -2 {{1}} {{file1}} {{file2}}
• Produce a line for each unpairable line for file1:
  join -a {{1}} {{file1}} {{file2}}
• Join a file from stdin:
  cat {{path/to/file1}} | join - {{path/to/file2}}