linux中Shell並發編程樣本

在Python中，有很多模組都可以實現並發編程，比如 threading, processing, eventlet 與 Stackless Python 等。

那麼對於Shell而言，又如何?呢？其實原理很簡單，我採用的方法是：
1. 將需要執行的任務分批放入後台執行；
2. 將後台執行的命令結果匯總到指定的檔案中;
3. 使用wait命令來等待所有任務執行結束。

下面的指令碼就用到了這樣的並發編程方法，實現的功能是：
快速(3-4秒內)對相同C網內的所有IP(255個)通過命令ping進行測試並返回結果。

代碼如下

複製代碼

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 $1 |sed 's/＼./ /g') do   count=$((${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 [ "$2" == "unable" ]; then   status="unpingable" else   status="pingable" fi # ping as paraller mode and write output into file for i in {1..255} do   ${status} & done # wait for all ping processes done wait # print output with better order sum=$(wc -l ${output} |awk '{print $1}') echo "There are ＼"${sum}＼" ＼"${status}＼" IPs begin with ＼"${subnet}.＼" :" cat ${output} | sort -t"." -k1,1n -k2,2n -k3,3n -k4,4n | xargs -n 20 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 "142" "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