pipe(2) - NetBSD Manual Pages

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PIPE(2)                   NetBSD System Calls Manual                   PIPE(2)


NAME

     pipe -- create descriptor pair for interprocess communication


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     int
     pipe(int fildes[2]);


DESCRIPTION

     The pipe() function creates a pipe, which is an object allowing unidirec-
     tional 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

     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

     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

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


STANDARDS

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


HISTORY

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

NetBSD 3.1                       July 17, 1994                      NetBSD 3.1