Introduction to Unix

4.7. The Pipe (|)

A pipe is a facility of the shell that makes it very easy to chain together multiple commands. A pipe is called upon with the vertical bar character (|). When used between two Unix commands, it means that output from the first command should become the input to the second command. For example, to count how many files underneath a directory have been modified in the last day, the find and wc commands may be used along with a pipe (Finding Files, Counting with wc). The find command will list the modified files and wc can count them:

find . -type f -mtime -1 | wc -l

To send out from stderr to the same pipe that stdout was sent to, put |&, which is short for 2>&1 | at the end of the command.

find . -type f -mtime -1 | wc -l |&