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Name

pipe - create an interprocess channel

Synopsis

#include <unistd.h>

int pipe(int fildes[2]);

MT-Level

Async-Signal-Safe

Description

pipe() creates an I/O mechanism called a pipe and returns two file descriptors, fildes[0] and fildes[1]. The files associated with fildes[0] and fildes[1] are streams and are both opened for reading and writing. The O_NDELAY and O_NONBLOCK flags are cleared.

A read from fildes[0] accesses the data written to fildes[1] on a first-in-first-out (FIFO ) basis and a read from fildes[1] accesses the data written to fildes[0] also on a FIFO basis.

The FD_CLOEXEC flag will be clear on both file descriptors.

Upon successful completion pipe() marks for update the st_atime, st_ctime, and st_mtime fields of the pipe.

Return Values

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

Errors

pipe() fails if:

EMFILE
If {OPEN_MAX}-1 or more file descriptors are currently open for this process.
ENFILE
A file table entry could not be allocated.

See Also

sh(1) , fcntl(2) , getmsg(2) , poll(2) , putmsg(2) , read(2) , write(2) , streamio(7I)

Notes

Since a pipe is bi-directional, there are two separate flows of data. Therefore, the size (st_size) returned by a call to fstat () with argument fildes[0] or fildes[1] is the number of bytes available for reading from fildes[0] or fildes[1] respectively. Previously, the size (st_size) returned by a call to fstat() with argument fildes[1] (the write-end) was the number of bytes available for reading from fildes[0] (the read-end).

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