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PIPE(2)                     BSD System Calls Manual                    PIPE(2)

     pipe -- create descriptor pair for interprocess communication

     #include <unistd.h>

     pipe(int fildes[2]);

     The pipe() function creates a pipe (an object that allows unidirectional
     data flow) and allocates a pair of file descriptors.  The first descrip-tor descriptor
     tor connects to the read end of the pipe; the second connects to the
     write end.

     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; the
     sink's standard input is set up to be the read end of the pipe.  The pipe
     itself persists until all of 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.

     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.

     The pipe() call will fail if:

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

     [EMFILE]           Too many descriptors are active.

     [ENFILE]           The system file table is full.

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

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

4th Berkeley Distribution        June 4, 1993        4th Berkeley Distribution