pipe2(2) [freebsd man page]

PIPE(2) 						      BSD System Calls Manual							   PIPE(2)

NAME

     pipe, pipe2 -- create descriptor pair for interprocess communication

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     pipe(int fildes[2]);

     int
     pipe2(int fildes[2], int flags);

DESCRIPTION

     The pipe() system call creates a pipe, which is an object allowing bidirectional data flow, and allocates a pair of file descriptors.

     The pipe2() system call allows control over the attributes of the file descriptors via the flags argument.  Values for flags are constructed
     by a bitwise-inclusive OR of flags from the following list, defined in <fcntl.h>:

     O_CLOEXEC	 Set the close-on-exec flag for the new file descriptors.

     O_NONBLOCK  Set the non-blocking flag for the ends of the pipe.

     If the flags argument is 0, the behavior is identical to a call to pipe().

     By convention, the first descriptor is normally used as the read end of the pipe, and the second is normally the write end, so that data
     written to fildes[1] appears on (i.e., can be read from) fildes[0].  This allows the output of one program to be sent to another program: the
     source's standard output is set up to be the write end of the pipe, and the sink's standard input is set up to be the read end of the pipe.
     The pipe itself persists until all its associated descriptors are closed.

     A pipe that has had an end closed is considered widowed.  Writing on such a pipe causes the writing process to receive a SIGPIPE signal.
     Widowing a pipe is the only way to deliver end-of-file to a reader: after the reader consumes any buffered data, reading a widowed pipe
     returns a zero count.

     The bidirectional nature of this implementation of pipes is not portable to older systems, so it is recommended to use the convention for
     using the endpoints in the traditional manner when using a pipe in one direction.

RETURN VALUES

     The pipe() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate
     the error.

ERRORS

     The pipe() and pipe2() system calls will fail if:

     [EMFILE]		Too many descriptors are active.

     [ENFILE]		The system file table is full.

     [ENOMEM]		Not enough kernel memory to establish a pipe.

     The pipe2() system call will also fail if:

     [EINVAL]		The flags argument is invalid.

SEE ALSO

     sh(1), fork(2), read(2), socketpair(2), write(2)

HISTORY

     The pipe() function appeared in Version 3 AT&T UNIX.

     Bidirectional pipes were first used on AT&T System V Release 4 UNIX.

     The pipe2() function appeared in FreeBSD 10.0.

BSD
								    May 1, 2013 							       BSD

Check Out this Related Man Page

pipe(2) 							   System Calls 							   pipe(2)

NAME

       pipe - create an interprocess channel

SYNOPSIS

       #include <unistd.h>

       int pipe(int fildes[2]);

DESCRIPTION

       The  pipe() function 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, O_NONBLOCK, and FD_CLOEXEC	flags  are
       cleared on both file descriptors. The fcntl(2) function can be used to set these flags.

       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.

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

RETURN VALUES

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

ERRORS

       The pipe() function will fail if:

       EMFILE	       More than {OPEN_MAX} 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.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sh(1), fcntl(2), fstat(2), getmsg(2), poll(2), putmsg(2), read(2), write(2), attributes(5), standards(5), 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(2)  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 5.10							    23 Apr 2002 							   pipe(2)

Linux and UNIX Man Pages

pipe2(2) [freebsd man page]

Check Out this Related Man Page