NAME    [Toc]    [Back]

     pipe - create descriptor pair for interprocess communication

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

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-of-file 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.  The reliable detection of this
                        error cannot be guaranteed; when not detected, a signal
 may be delivered to the process, indicating an
                        address violation.

SEE ALSO    [Toc]    [Back]

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

STANDARDS    [Toc]    [Back]

     The pipe() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1'').

HISTORY    [Toc]    [Back]

     A pipe() function call appeared in Version 6 AT&T UNIX.

BSD                              July 17, 1994                             BSD