.ds FN /sys/man/2/pipe
.so src2
\&.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.