pipe(2)

NAME

     pipe - create an interprocess channel

SYNOPSIS

     #include <unistd.h>

     int pipe(int fildes[2]);

DESCRIPTION

     The pipe() function 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 O_NDELAY and O_NONBLOCK flags are cleared.

     A read from fildes[0] accesses the data written to fildes[1]
     on  a  first-in-first-out  (FIFO)  basis  and  a  read  from
     fildes[1] accesses the data written to fildes[0] also  on  a
     FIFO basis.

     The FD_CLOEXEC flag will be clear on both file descriptors.

     Upon successful  completion  pipe()  marks  for  update  the
     st_atime, st_ctime, and st_mtime fields of the pipe.

RETURN VALUES

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

ERRORS

     The pipe() function will fail if:

     EMFILE
           There  are   OPEN_MAX-1  or  more   file   descriptors
           currently open for this process.

     ENFILE
           A file table entry could not be allocated.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | Async-Signal-Safe           |
    |_____________________________|_____________________________|

SEE ALSO

     sh(1), fcntl(2), fstat(2),  getmsg(2),  poll(2),  putmsg(2),
     read(2), write(2), attributes(5), streamio(7I)

NOTES

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