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PIPE(2)                       System Calls Manual                      PIPE(2)

     pipe, pipe2 - create descriptor pair for interprocess communication

     Standard C Library (libc, -lc)

     #include <unistd.h>

     pipe(int fildes[2]);

     #include <fcntl.h>
     #include <unistd.h>

     pipe2(int fildes[2], int flags);

     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.

     The pipe2() function behaves exactly like pipe() only it allows extra
     flags to be set on the returned file descriptor.  The following flags are

           O_CLOEXEC   Set the "close-on-exec" property.

           O_NONBLOCK  Sets non-blocking I/O.

                       Return EPIPE instead of raising SIGPIPE.

     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() and pipe2() calls will fail if:

     [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.

     [EMFILE]           Too many descriptors are active.

     [ENFILE]           The system file table is full.

     [ENOMEM]           Not enough kernel memory to establish a pipe.

     pipe2() will also fail if:

     [EINVAL]           flags contains an invalid value.

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

     The pipe() function conforms to IEEE Std 1003.1-1990 ("POSIX.1").

     A pipe() function call appeared in Version 3 AT&T UNIX.  Since Version 4
     AT&T UNIX, it allocates two distinct file descriptors.

     The pipe2() function is inspired from Linux and appeared in NetBSD 6.0.

NetBSD 10.99                   November 27, 2020                  NetBSD 10.99