The magic of "&" in shell -- implementing multi-process concurrency

A simple dd script is written for testing, as follows #! /Bin/shfor (i1; I & lt; 5; I ++); do {ddif/mnt/ufstest/test $ I. when running tsof/dev/nullbs480K} done, dd can only read one file at the same time, which does not work for me. I wanted to implement more...

A simple dd script is written for testing.

#! /Bin/sh
For (I = 1; I <= 5; I ++); do
{
Dd if =/mnt/ufstest/test $ I. ts of =/dev/null bs = 480 K
}
Done
During execution, I found that dd can only read one file at the same time, not achieving my effect. I wanted to implement concurrent read performance measurement for multiple dd processes.

650) this. width = 650; "src =" http://up.2cto.com/2011/0930/20110930095733665.png "style =" border-top-width: 0px; padding-right: 0px; padding-left: 0px; border-left-width: 0px; border-bottom-width: 0px; padding-bottom: 0px; margin: 0px; vertical-align: top; padding-top: 0px; border-right-width: 0px "title =" image "/>

 

Google Now, you only need to add "&" to achieve multi-concurrency.

#! /Bin/sh
For (I = 1; I <= 5; I ++); do
{
Dd if =/mnt/ufstest/test $ I. ts of =/dev/null bs = 480 K&
}
Done

Results:

650) this. width = 650; "src =" http://up.2cto.com/2011/0930/20110930095734732.png "style =" border-top-width: 0px; padding-right: 0px; padding-left: 0px; border-left-width: 0px; border-bottom-width: 0px; padding-bottom: 0px; margin: 0px; vertical-align: top; padding-top: 0px; border-right-width: 0px "title =" image "/>

Author: "star & storage"