#include <unistd.h>

int pipe(int fildes[2]);


Partially implemented


IEEE Std 1003.1-2017


The pipe() function shall create a pipe and place two file descriptors, one each into the arguments fildes[0] and fildes[1], that refer to the open file descriptions for the read and write ends of the pipe. The file descriptors shall be allocated as described in File Descriptor Allocation. The O_NONBLOCK and FD_CLOEXEC flags shall be clear on both file descriptors. (The fcntl() function can be used to set both these flags.)

Data can be written to the file descriptor fildes[1] and read from the file descriptor fildes[0]. A read on the file descriptor fildes[0] shall access data written to the file descriptor fildes[1] on a first-in-first-out basis.

It is unspecified whether fildes[0] is also open for writing and whether fildes[1] is also open for reading.

A process has the pipe open for reading (correspondingly writing) if it has a file descriptor open that refers to the read end, fildes[0] (write end, fildes[1]).

The pipe's user ID shall be set to the effective user ID of the calling process.

The pipe's group ID shall be set to the effective group ID of the calling process.

Upon successful completion, pipe() shall mark for update the last data access, last data modification, and last file status change timestamps of the pipe.

Return value

Upon successful completion, 0 shall be returned; otherwise, -1 shall be returned and errno set to indicate the error, no file descriptors shall be allocated and the contents of fildes shall be left unmodified.


The pipe() function shall fail if:

  • EMFILE - All, or all but one, of the file descriptors available to the process are currently open.

  • ENFILE - The number of simultaneously open files in the system would exceed a system-imposed limit.



Known bugs


See Also

  1. Standard library functions
  2. Table of Contents