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pipe - create an interprocess channel
The pipe system call creates an I/O mechanism called a pipe. The file descriptors
returned can be used in read and write operations. When the pipe is written using the
descriptor fildes up to 4096 bytes of data are buffered before the writing process is
suspended. A read using the descriptor fildes will pick up the data. Writes with a
count of 4096 bytes or less are atomic; no other process can intersperse data.
It is assumed that after the pipe has been set up, two (or more) cooperating processes
(created by subsequent fork calls) will pass data through the pipe with read and write
The Shell has a syntax to set up a linear array of processes connected by pipes.
Read calls on an empty pipe (no buffered data) with only one end (all write file descrip-
tors closed) returns an end-of-file.
sh(1), read(2), write(2), fork(2)
The function value zero is returned if the pipe was created; -1 if too many files are
already open. A signal is generated if a write on a pipe with only one end is attempted.
Should more than 4096 bytes be necessary in any pipe among a loop of processes, deadlock
(pipe = 42.)
(read file descriptor in r0)
(write file descriptor in r1)
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