| PIPE(2) | System Calls Manual | PIPE(2) | 
pipe, pipe2 —
#include <unistd.h>
int
  
  pipe(int
    fildes[2]);
#include <fcntl.h>
  
  #include <unistd.h>
int
  
  pipe2(int
    fildes[2], int
    flags);
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 valid:
O_CLOEXECO_NONBLOCKO_NOSIGPIPEEPIPE instead of raising
      SIGPIPE.pipe() and pipe2() calls
  will fail if:
EFAULT]EMFILE]ENFILE]ENOMEM]pipe2() will also fail if:
EINVAL]pipe() function conforms to IEEE
  Std 1003.1-1990 (“POSIX.1”).
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.
| November 27, 2020 | NetBSD 10.0 |