# Pipe
A pipe is an unidirectional [IPC](ipc.md) mechanism used first in the [Unix](unix.md) operating system, used to connect one
or multiple processes together (then forming a pipeline). Pipes are a central concept in Unix-like operating systems as it
allows the composition of multiple programs results without using temporary files.

In a shell a pipeline is constructed using the `|` character which by default redirect the process stdout
output to the stdin of the process at the right of the pipe.
```sh
cmdA | cmdB | cmdC | cmdD
```

## Named pipes
A named pipe also known as a FIFO, is a pipe that is represented as a file on a disk having similar semantics
to a regular file.
```sh
mkfifo foo              # create named pipe
cat foo &               # will block until something is written to it
echo 'test' > foo       # send data through the pipe
```