NAME    [Toc]    [Back]

     pipe - create descriptor pair for interprocess communication

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>

     int
     pipe(int fildes[2]);

DESCRIPTION    [Toc]    [Back]

     The  pipe()  function creates a pipe, which is an object allowing unidirectional
 data flow, and allocates a pair of file  descriptors.
The first
     descriptor  connects  to  the  read end of the pipe, and the
second connects
     to 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 whose read or write end has been 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-offile to a
     reader: after the reader consumes any buffered data, reading
a widowed
     pipe returns a zero count.

RETURN VALUES    [Toc]    [Back]

     On  successful creation of the pipe, zero is returned.  Otherwise, a value
     of -1 is returned and the variable errno set to indicate the
error.

ERRORS    [Toc]    [Back]

     The pipe() call will fail if:

     [EMFILE]      Too many descriptors are active.

     [ENFILE]      The system file table is full.

     [EFAULT]      The fildes buffer is in an invalid area of the
process's
                   address space.

SEE ALSO    [Toc]    [Back]

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

STANDARDS    [Toc]    [Back]

     The  pipe()  function  conforms  to  IEEE  Std   1003.1-1988
(``POSIX'').

     As  an  extension,  the pipe provided is actually capable of
moving data
     bidirectionally.  This is compatible  with  SVR4.   However,
this is nonPOSIX
  behaviour  which should not be relied on, for reasons
of portability.

HISTORY    [Toc]    [Back]

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

OpenBSD      3.6                           June      4,      1993