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.

Debian                                             May 1, 2013                                           PIPE(2)