TH PIPE 2
SH NAME
pipe \- create an interprocess channel
SH SYNOPSIS
B #include <u.h>
br
B #include <libc.h>
PP
B
int pipe(int fd[2])
SH DESCRIPTION
I Pipe
creates a buffered channel for interprocess I/O communication.
Two file descriptors are returned in
IR fd .
Data written to
B fd[1]
is available for reading from
B fd[0]
and data written to
B fd[0]
is available for reading from
BR fd[1] .
PP
After the pipe has been established,
cooperating processes
created by subsequent
IR fork (2)
calls may pass data through the
pipe with
I read
and
I write
calls.
The bytes placed on a pipe
by one
I write
are contiguous even if many processes are writing.
Write boundaries are preserved: each read terminates
when the read buffer is full or after reading the last byte
of a write, whichever comes first.
PP
The number of bytes available to a
IR read (2)
is reported
in the
B Length
field returned by
I fstat
or
I dirfstat
on a pipe (see
IR stat (2)).
PP
When all the data has been read from a pipe and the writer has closed the pipe or exited,
IR read (2)
will return 0 bytes. Writes to a pipe with no reader will generate a note
BR "sys: write on closed pipe" .
SH SOURCE
B /sys/src/libc/9syscall
SH SEE ALSO
IR intro (2),
IR read (2),
IR pipe (3)
SH DIAGNOSTICS
Sets
IR errstr .
SH BUGS
If a read or a write of a pipe is interrupted, some unknown
number of bytes may have been transferred.
br
When a read from a pipe returns 0 bytes, it usually means end of file
but is indistinguishable from reading the result of an explicit
write of zero bytes.
