PIPE(2) | System Calls Manual | PIPE(2) |
pipe
, pipe2
—
#include <unistd.h>
int
pipe
(int
fildes[2]);
#include
<unistd.h>
#include <fcntl.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_CLOEXEC
O_NONBLOCK
O_NOSIGPIPE
EPIPE
instead of raising
SIGPIPE
.pipe
() and pipe2
() calls
will fail if:
EFAULT
]EMFILE
]ENFILE
]pipe2
() will also fail if:
EINVAL
]pipe
() function conforms to IEEE
Std 1003.1-1990 (“POSIX.1”).
pipe
() function call appeared in
Version 6 AT&T UNIX. The
pipe2
() function is inspired from Linux and appeared
in NetBSD 6.0.
January 23, 2012 | NetBSD 9.0 |