|PIPE(2)||System Calls Manual||PIPE(2)|
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
pipe2() 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
pipe2() function appeared in OpenBSD 5.7.
|December 10, 2014||OpenBSD-current|