|PIPE(2)||System Calls Manual||PIPE(2)|
— create descriptor pair for interprocess
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 appears on (i.e., can be read from)
fildes. 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.
pipe2() function is identical to
pipe() except that the non-blocking I/O mode on both
ends of the pipe is determined by the
flag in the flags argument and the close-on-exec flag
on both the new file descriptors is determined by the
O_CLOEXEC flag in the flags
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
will succeed unless:
pipe2() may return the
pipe() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”). The
pipe2() function is expected to conform to a future
revision of that standard.
As an extension, the pipe provided is actually capable of moving data bidirectionally. This is compatible with SVR4. However, this is non-POSIX behaviour which should not be relied on, for reasons of portability.
pipe() function call appeared in
Version 3 AT&T UNIX. Since
Version 4 AT&T UNIX, it allocates two
distinct file descriptors. The
appeared in OpenBSD 5.7.
|December 10, 2014||OpenBSD-6.1|