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.TH PUMP 1
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.SH NAME
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pump \- copy asynchronously via a large circular buffer
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.SH SYNOPSIS
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.B pump
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[
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.B -b
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.I iando
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] [
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.B -d
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.I sleepms
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] [
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.B -f
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.I ofile
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] [
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.B -i
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.I ireadsize
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] [
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.B -k
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.I KB-buf
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] [
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.B -o
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.I owritesize
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] [
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.B -s
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.I start-KB
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] [
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.B -S
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.I off
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] [
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.B -t
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.I minutes
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] [
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.I file
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\&... ]
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.SH DESCRIPTION
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.I Pump
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copies
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.IR files
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(or standard input if none)
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to standard output
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by using two processes,
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one reading and one writing,
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sharing a large circular buffer,
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thus permitting the reading process to
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get ahead of the writing process if the
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output device is slow (e.g., an optical disc).
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This in turn can keep the output device busy.
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The pipeline
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.L "dd | dd"
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can approximate this, but pipe buffering is limited to 64K
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bytes, which is fairly modest.
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.PP
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Options are:
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.TF \fL-m
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.TP
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.B -b
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sets the size of
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.I read
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and
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.I write
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operations to
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.I iando
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bytes.
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The default size is 8 kilobytes.
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.TP
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.B -d
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causes the output process to sleep for
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.I sleepms
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milliseconds initially, giving the reading
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process time to accumulate data in the buffer.
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.TP
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.B -f
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writes
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.I ofile
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rather than standard output
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.TP
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.B -i
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sets the size of
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.I read
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operations to
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.I ireadsize
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bytes.
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.TP
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.B -k
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allocates a circular buffer of
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.I KB-buf
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kilobytes rather than the default
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5000 kilobytes.
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.TP
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.B -o
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sets the size of
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.I write
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operations to
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.I owritesize
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bytes.
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.TP
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.B -s
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prevents output until
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.I start-KB
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kilobytes have been read.
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.TP
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.B -S
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seeks both input and output files to
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.I off
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before copying.
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.TP
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.B -t
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stops output after
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.I minutes
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have passed.
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This assumes that
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.I pump
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can copy 10,584,000 bytes per minute.
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.SH EXAMPLES
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Append a
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.IR venti (8)
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arena to a DVD or BD quickly.
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.PD 0
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.IP
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.EX
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cdfs
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venti/rdarena arena0 arena.3 |
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	pump -b 65536 -k 51200 >/mnt/cd/wd/arena.3
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.EE
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.PD
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.\" .SH FILES
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.SH SOURCE
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.B /sys/src/cmd/pump.c
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.SH SEE ALSO
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.IR cp (1),
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.IR dd (1),
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.IR ecp (1),
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.IR cdfs (4)
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.SH BUGS
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.I Pump
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processes spin while waiting for the circular buffer
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to fill or drain.
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.PP
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.IR Dd ,
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.IR ecp
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and
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.I pump
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occupy slightly different niches
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but perhaps some simplification is possible.