10-07-2011
@Thanks alister.
The clarification was very helpful indeed.
While we are on the subject, (and I know there are scattered resources available on google for this), how is the pipe underlying structure implemented?
If it is just another file, is it possible to see the contents of the pipe {so as to know what's being passed on between the read and write ends}.
Finally,
Is there a way to find out which FDs point to the same underlying description?
If it's hidden somewhere in lsof, i'll dig deeper, but if not do let me know.
Thanks again. The community here on this site is much more forgiving towards the beginners.
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PIPE(2) System Calls Manual PIPE(2)
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 communication. 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. The bytes placed on a pipe by one 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.
The number of bytes available to a read(2) is reported in the Length field returned by fstat or dirfstat on a pipe (see stat(2)).
When all the data has been read from a pipe and the writer has closed the pipe or exited,
read(2) will return 0 bytes. Writes to a pipe with no reader will generate a note sys: write on closed pipe.
SOURCE
/sys/src/libc/9syscall
SEE ALSO
intro(2), read(2), pipe(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.
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.
PIPE(2)