PIPE(II) 8/5/73 PIPE(II) NAME pipe - create a pipe SYNOPSIS (pipe = 42.) sys pipe (read file descriptor in r0) (write file descriptor in r1) pipe(fildes) int fildes; DESCRIPTION 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 returned in r1 (resp. fildes), up to 4096 bytes of data are buffered before the writing process is suspended. A read using the descriptor returned in r0 (resp. fildes) will pick up the 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 calls. 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 descriptors closed) return an end-of- file. Write calls under similar conditions are ignored. SEE ALSO sh(I), read(II), write(II), fork(II) DIAGNOSTICS The error bit (c-bit) is set if more than 8 files are already open. From C, a -1 returned value indicates an error.