一个 Shell 程序的性能优化

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#!/bin/bash
#Author Xsh  date:08-15-2006
echo "Time:$(date)==>Strat to processing........." #显示程序开始运行时间
while read numseg
  	do
  	 tmplow="${tmplow} $(expr substr ${numseg} 1 10 & >/dev/null ) " 
  	 tmptop="${tmptop} $(expr substr ${numseg} 12 10 & >/dev/null ) "
done < ./numseg.txt	#循环读取号段文件下限号段存入变量tmplow，上限号段存入变量tmptop

arr_lownug=(${tmplow}) #将下限号段存入数组arr_lownug
arr_topnug=(${tmptop})	#将上限号段存入数组arr_topnug

#定义函数checknum()，输入参数为需要检查的"计费号码"，输出参数为0或者1
#函数checknum()输出为0 表示"计费号码" 不在号段文件的所有号段范围内
#函数checknum()输出为1 表示"计费号码" 在号段文件的所有号段范围内
#函数checknum()中用二分搜索法进行号码的判断
checknum(){ ＃函数定义开始
   thisnum=$1
   ckresult=0
   lowflag=0
   topflag=$((${#arr_lownug[*]} - 1 ))   #标注1
   MaxIndex=$((${#arr_topnug[*]} - 1 ))  #标注2
   midflag=0
   midflag=$((${topflag} / 2 ))	      #标注3
if [ "${thisnum}" \< "${arr_lownug[0]}" -o "${thisnum}" \> "${arr_topnug[${MaxIndex}]}" ]
then
	return 0
else

while [ "$lowflag" != "$midflag" ]
do
 if ["$thisnum"\> "${arr_lownug[${midflag}]}" -o "$thisnum" == \
  "${arr_lownug[${midflag}]}"]
   then
   lowflag=${midflag}
   midflag=$(( $((${topflag} + ${lowflag})) / 2 )) #标注4
elif["$thisnum"\<"${arr_lownug[${midflag}]}" -o "$thisnum" == \
"${arr_lownug[${midflag}]}"] 
then    
     topflag=${midflag}
     midflag=$(($((${topflag} + ${lowflag})) / 2 )) #标注5
else
  echo "Error!"   
fi
done 
if ["$thisnum" \< "${arr_topnug[${lowflag}]}" -o "$thisnum" == \
"${arr_topnug[${lowflag}]}"]
then
 return 1
else 
 return 0 
fi
fi
}＃函数定义结束

while read f
do
org="${f:0:10}"  #标注6
checknum ${org}
returnval=$?
if [ "$returnval" == "1"  ]
then 
echo "${f}" >> ./Match_result.cdr  #将匹配的记录存入结果文件1
else
echo "${f}" >> ./NoMatch_result.cdr #将不匹配的记录存入结果文件2
fi
done < ./rttest.txt 
echo "Time:$(date) ==> Proccess is end! "
exit 0;