通过本脚本，发现bash确实在算术运算方面比老的shell要强大，为此需要开始学习bash，以利用它强大的功能。不过bash中的for语句功能和c中差异比较大。
# cat stream #! /bin/bash # Write by Neil.xu qq:37391319 email: xurongzhong@gmail.com # 2008-8-19 we need to monitor streams of LTS channels, so write this script typeset in in_old dif_in dif_in1 dif_out1 typeset out out_old dif_out in_old=$(cat /proc/net/dev | grep eth0 | sed 's=^.*:==' | awk '{ print $1 }' ) out_old=$(cat /proc/net/dev | grep eth0 | sed 's=^.*:==' | awk '{ print $9 }') while true do sleep 1 in=$(cat /proc/net/dev | grep eth0 | sed 's=^.*:==' | awk '{ print $1 }') out=$(cat /proc/net/dev | grep eth0 | sed 's=^.*:==' | awk '{ print $9 }') dif_in=$((in-in_old)) dif_in1=$((dif_in * 8 / 1024 / 1024 )) dif_out=$((out-out_old)) echo " IN: ${dif_in} bytes OUT: ${dif_out} bytes " dif_out1=$((dif_out * 8 / 1024 / 1024 )) echo "IN: ${dif_in1} mbps OUT: ${dif_out1} mbps" in_old=${in} out_old=${out} done |
运行效果：
# ./stream IN: 349179 bytes OUT: 1363936 bytes IN: 2 mbps OUT: 10 mbps IN: 349612 bytes OUT: 1361852 bytes IN: 2 mbps OUT: 10 mbps IN: 348684 bytes OUT: 1358952 bytes IN: 2 mbps OUT: 10 mbps IN: 349998 bytes OUT: 1359092 bytes |
