pipe(2)                                                             pipe(2)

NAME
     pipe - create an interprocess communication channel

SYNOPSIS
     #include <unistd.h>

     int pipe(int fildes[2]);

DESCRIPTION
     pipe() 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 ONDELAY and ONONBLOCK flags are cleared.

     A read from fildes[0] accesses the data written to fildes[1] on a FIFO
     basis and a read from fildes[1] accesses the data written to fildes[0]
     also on a FIFO basis. It is unspecified whether fildes[0] is also open
     for writing and whether fildes[1] is also open for reading.

     The FDCLOEXEC flag will be clear on both file descriptors.

     Upon successful completion pipe() marks for update the statime,
     stctime, and stmtime fields of the pipe.

ERRORS
     The following error code descriptions are function-specific. You will
     find a general description in introprm2(2) or in errno(5).

     pipe() fails if:

     EMFILE    If OPENMAX-1 or more file descriptors are currently open
               for this process.

     ENFILE    A file table entry could not be allocated.

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

NOTES
     Since a pipe is bi-directional, there are two separate flows of data.
     Therefore, the size (stsize) 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
     (stsize) 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).

SEE ALSO
     sh(1), fcntl(2), getmsg(2), poll(2), putmsg(2), read(2), write(2),
     unistd(4), streamio(7).




Page 1                       Reliant UNIX 5.44                Printed 11/98