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This article introduces the relevant knowledge of "how to achieve shell multithreaded programming under Linux". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Multithreaded programming in Linux has the advantages of improving the response of applications and making multi-cpu systems more effective. The following editor will explain the process of multithreaded programming through the example of shell multithreaded programming under Linux.

#! / bin/bash

#

# this example illustrates a technique for simulating multithreading with wait and read commands

# this technique is often used for multi-host checking, such as ssh login, ping, etc., where a single process is slow and does not cost cpu

# also explains the control of multithreading

#

Function a_sub

{

# A function is defined here as a thread (child process)

The function of sleep 3 # thread is sleep 3s

}

Tmp_fifofile= "/ tmp/$.fifo" mkfifo $tmp_fifofile # create a new file of type fifo

Exec 6 "$tmp_fifofile # points fd6 to fifo type

Rm $tmp_fifofile thread=15 # the number of threads is defined here

For

((iTuno "$thread;i++)); do echo

Done "& 6 # actually put $thread carriage return in fd6.

For

Do # 50 cycles, which can be understood as 50 hosts, or other

Read-U6 # A read-U6 command executes once, subtracts a carriage return from fd6, and then executes down

When there is no carriage return in # fd6, it stops here to control the number of threads.

{# this virgin subprocess starts to execute and is placed in the background

A_sub & &

{# this can be used to determine the logic of a child process

Echo "a_sub is finished"

}

| | |

{echo "sub error"

}

Echo "& 6 # when the process is over, add a carriage return to the fd6, that is, add the one subtracted by read-U6

}

& done wait # waits for all backstage subprocesses to finish

Exec 6 "&-# close df6 exit 0

Description:

Commands in this program

Mkfifo tmpfile

And commands in linux

Mknod tmpfile p

Effective? The results are the same. The difference is that mkfifo is the POSIX standard, so it is recommended. This command creates a first-in, first-out pipe file and assigns it a file marker of 6. It is important to note that pipe files are a way of communicating between processes.

Exec 6 "$tmp_fifofile # points fd6 to fifo type

Without this sentence, when writing data to the file $tmp_fifofile or & 6, the program will be blocked until a read reads the data in the pipe file. After executing the above sentence, you can continue to write data to files of type fifo without blocking while the program is running, and the data will be saved for read programs to read.

By running the command:

Time . / multithread.sh "/ dev/null

Final operation time: 50 amp 15 = 3 groups (15 each) + 1 group (5 "15 form a group) = 4 groups, each group takes 3 seconds

Then 3 * 4 = 12 seconds.

Traditional non-multithreaded code operation time: 50 * 3 = 150 seconds.

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