Pipe (computing)

Pipe is the name of the ASCII character at position 124 (decimal): |

---

In the context of Unix operating systems, as well as other Operating Systems like MS-DOS, a pipe signifies that the output of one program ("stdout") feeds directly as input ("stdin") to another program. Any error messages from the first program ("stderr") are not passed on through the pipe. The Unix shell uses the pipe character ( | ) to join programs together. A sequence of commands joined together by pipes is known as a pipeline. Often filter programs form the constituent programs in a pipeline -- see Pipes and filters.

An example of a pipeline, which should print the numbers from 1 to 13:

while : ; do echo ; done | head -n 13 | nl -ba

The pipe character is also (was originally?) drawn as a broken bar ( ¦ ), and usually depicted so on Microsoft Windows keyboards. (Except that I've only seen it on keyboards without the windows key, but have seen it on all dos keyboards.)

---

See pipe for other uses of the word.