|PIPE(2)||System Calls Manual||PIPE(2)|
pipe — create
descriptor pair for interprocess communication
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.
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.
pipe() call will fail if:
pipe() function conforms to
IEEE Std 1003.1-1988 (“POSIX.1”).
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.
|May 31, 2007||OpenBSD-5.1|