pipe – create an interprocess channel|
int pipe(int fd)
Pipe creates a buffered channel for interprocess I/O communication.
Two file descriptors are returned in fd. Data written to fd
is available for reading from fd and data written to fd
is available for reading from fd.
After the pipe has been established, cooperating processes created
by subsequent fork(2) calls may pass data through the pipe with
read and write calls.
When all the data has been read from a pipe and the writer has
closed the pipe or exited, read(3) will return 0 bytes. Writes
to a pipe with no reader will generate a note sys: write on closed
If a read or a write of a pipe is interrupted, some unknown number
of bytes may have been transferred.
Pipe is a macro defined as p9pipe to avoid name conflicts with
Unix’s pipe system call.
Unix pipes are not guaranteed to be bidirectional. In order to
ensure a bidirectional channel, p9pipe creates Unix domain sockets
via the socketpair(2) instead of Unix pipes.
The implementation of pipes as Unix domain sockets causes problems
with some Unix implementations of /dev/fd, Unix’s dup device.
If a Unix domain socket is open as file descriptor 0, some implementations
disallow the opening of /dev/fd/0; instead one must connect(2)
to it. If this functionality is important (as it is for rc(1)),
one must #undef
pipe and fall back on the (possibly unidirectional) Unix pipes.|