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(3) 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(3); see also write(3) .

FUTURE DIRECTIONS

None.

SEE ALSO

fcntl(3) , read(3) , write(3) , the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), <fcntl.h>, <unistd.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

• The DESCRIPTION is updated to indicate that certain dispositions of fildes [0] and fildes [1] are unspecified.

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