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Is there a utility that I can stick in a pipeline to decouple read and write speeds?

$ producer | buf | consumer

Basically, I want a utility buf that reads its input as fast as possible, storing it in memory so consumer can take its sweet time while producer runs as fast as possible.

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3 Answers

The pv (pipe viewer) utility can do this (with the -B option) and a lot more, including giving you progress reports.

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Is there a way to do this with an unbounded amount of data? As best as I can tell, I need to supply a number with -B and if the producer gets that far ahead of the consumer, the producer will slow down again. If you're in a situation where there are multiple consumers (producer | tee >(pv -cB $SIZE | consumer1) | pv -cB $SIZE2 | consumer2), this can cause slowdowns again. –  Daniel H Jun 17 '13 at 16:40
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you can use dd:

producer | dd bs=64K | consumer

It's available on every unix.

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+1 for using standard utility, although pv is probably is probably nicer to use (shows progress). –  Totor Mar 17 '13 at 15:17
Does that actually decouple the reading and writing speed? It seems like dd only stores one block at a time, so it would just delay everything by the amount of time it takes to produce the block size; please correct me if I'm wrong. Also, can this buffering be extended to unlimited size, or only whatever's entered for the block size? –  Daniel H Jun 17 '13 at 16:45
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Take a look at mbuffer. It can buffer to memory or memory mapped file(-t/-T).

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As I asked for the others, is there a way to tell it to buffer as much as is necessary, or does it have a maximum size? Is there a conceptual reason why most of these programs do have maximum sizes and don't, for example, use a linked list of smaller buffers (or any other arbitrary-size queue implementation)? –  Daniel H Jun 19 '13 at 22:11
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