pipe (3p) - Linux Manuals

pipe: create an interprocess channel

PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

pipe - create an interprocess channel

SYNOPSIS

#include <unistd.h>

int pipe(int fildes[2]);

DESCRIPTION

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. Their integer values shall be the two lowest available at the time of the pipe() call. 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]).

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

RETURN VALUE

Upon successful completion, 0 shall be returned; otherwise, -1 shall be returned and errno set to indicate the error.

ERRORS

The pipe() function shall fail if:

EMFILE

More than {OPEN_MAX} minus two file descriptors are already in use by this process.

ENFILE

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

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

The wording carefully avoids using the verb "to open" in order to avoid any implication of use of open(); see also write() .

FUTURE DIRECTIONS

None.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .