PIPE(3) PIPE(3)
NAME
pipe - create an interprocess channel
SYNOPSIS
#include <u.h>
#include <libc.h>
int pipe(int fd[2])
DESCRIPTION
Pipe creates a buffered channel for interprocess I/O commu-
nication. Two file descriptors are returned in fd. Data
written to fd[1] is available for reading from fd[0] and
data written to fd[0] is available for reading from fd[1].
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 pipe.
SOURCE
/src/lib9/pipe.c
SEE ALSO
intro(3), read(3)
DIAGNOSTICS
Sets errstr.
BUGS
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 func-
tionality is important (as it is for rc(1)), one must #undef
PIPE(3) PIPE(3)
pipe and fall back on the (possibly unidirectional) Unix
pipes.