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Annotation of researchv10dc/dist/man/v4/man2/pipe.2, revision 1.1.1.1

1.1       root        1: .th PIPE II 8/5/73
                      2: .sh NAME
                      3: pipe \*- create a pipe
                      4: .sh SYNOPSIS
                      5: (pipe = 42.)
                      6: .br
                      7: .ft B
                      8: sys pipe
                      9: .br
                     10: .ft R
                     11: (read file descriptor in r0)
                     12: .br
                     13: (write file descriptor in r1)
                     14: .s3
                     15: .ft B
                     16: pipe(fildes)
                     17: .br
                     18: int fildes[2];
                     19: .ft R
                     20: .sh DESCRIPTION
                     21: The
                     22: .it pipe
                     23: system call
                     24: creates an I/O mechanism called a pipe.
                     25: The file descriptors returned can
                     26: be used in read and write operations.
                     27: When the pipe is written using the descriptor
                     28: returned in r1 (resp. fildes[1]),
                     29: up to 4096 bytes of data are buffered
                     30: before the writing process is suspended.
                     31: A read using the descriptor returned in r0
                     32: (resp. fildes[0])
                     33: will pick up the data.
                     34: .s3
                     35: It is assumed that after the
                     36: pipe has been set up,
                     37: two (or more)
                     38: cooperating processes
                     39: (created by subsequent
                     40: .it fork
                     41: calls)
                     42: will pass data through the
                     43: pipe with
                     44: .it read
                     45: and
                     46: .it write
                     47: calls.
                     48: .s3
                     49: The shell has a syntax
                     50: to set up a linear array of processes
                     51: connected by pipes.
                     52: .s3
                     53: Read calls on an empty
                     54: pipe (no buffered data) with only one end
                     55: (all write file descriptors closed)
                     56: return an end-of-file.
                     57: Write calls under similar conditions are ignored.
                     58: .sh "SEE ALSO"
                     59: sh(I), read(II), write(II), fork(II)
                     60: .sh DIAGNOSTICS
                     61: The error
                     62: bit (c-bit) is set if
                     63: more than
                     64: 8 files are already open.
                     65: From C, a \*-1 returned value
                     66: indicates an error.

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