NAME

pipe − create an interprocess channel

SYNOPSIS

#include <unistd.h>

int pipe(int fildes[2]);

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(7)

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). 

SunOS 5.4  —  Last change: 5 Jul 1990