Example of shell concurrent programming in Linux

In Python, there are many modules that enable concurrent programming, such as threading, processing, Eventlet, and Stackless python.

So how does it work for the shell? In fact, the principle is very simple, I used the method is:
1. The tasks that need to be carried out are put into the background;
2. Summary of the results of the command in the background to the specified file;
3. Use the wait command to complete the execution of all tasks.

The following script uses this concurrent programming method, which features:
Fast (within 3-4 seconds) test and return results for all IP (255) in the same C network by command Ping.

The code is as follows

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Vim fastping.sh #!/bin/bash # Default Settings SUBNET=$1 # C Type subnet Retry=2 # retry Times Timeout=3 # timeout seconds Output=/tmp/ping.output # Output File # function Print_help function Print_help () { echo "Examples:" Echo ${0} 172.17.32 Echo ${0} 192.168.1 Unable Exit 1 } # Check the parameter If [$#-lt 1]; Then Print_help Fi # Check the network parameter ' s format Count=0 For I in $ (echo $ |sed ' s/\.//g ') Todo count=$ ((${count}+1)) Done If [${count}-ne 3]; Then Print_help Fi # Clean the output file > ${output} function pingable () { Ping-c ${retry}-W ${timeout}-Q ${subnet}.${i} &>/dev/null && echo ${i} >> ${output} } function unpingable () { Ping-c ${retry}-W ${timeout}-Q ${subnet}.${i} &>/dev/null | | Echo ${i} >> ${output} } # Get the Check type If ["$" = "unable"]; Then Status= "Unpingable" Else Status= "Pingable" Fi # Ping as Paraller mode and write output into file For i in {1..255} Todo ${status} & Done # Wait for all ping processes done Wait # Print output with better order sum=$ (wc-l ${output} |awk ' {print $} ') echo "There are\" ${sum}\ "\ ${status}\" IPs begin With\ "${subnet}.\": " Cat ${output} | Sort-t "."-k1,1n-k2,2n-k3,3n-k4,4n | Xargs-n echo "" chmod +x fastping.sh ./fastping.sh Examples: ./fastping 172.17.32 ./fastping 192.168.1 Unable Time./fastping.sh 192.168.1 There are "pingable" IPs begin with "192.168.1": 1 10 12 13 14 15 16 18 19 20 21 22 23 24 25 26 27 28 29-30 31 32 33 34 35 36 37 38 40 41 42 43 44 45 46 47 48 49 50-51 52 53 54 55 56 57 59 60 61 62 63 64 65 66 67 68 69 70 71-72 73 74 75 76 77 78 80 81 83 84 85 86 87 88 89 90 91 92 93-94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 112 113 114 115 116-117 118 119 120 121 122 123 124 125 126 127 128 133 134 135 136 137 138 139 140-141 142 143 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165-166 170 254 Real 0m3.201s User 0m0.135s SYS 0m0.495s