流程结构

1 if [ $a == $b ]
2 then
3     echo "等于"
4 else
5     echo "不等于"
6 fi

case $xs in
0) echo "0" ;;
1) echo "1" ;;
*) echo "其他" ;;
esac

 1 # while true  等同   while :
 2 # 读文件为整行读入
 3 num=1
 4 while [ $num -lt 10 ]
 5 do
 6 echo $num
 7 ((num=$num+2))
 8 done
 9 ###########################
10 grep a  a.txt | while read a
11 do
12     echo $a
13 done
14 ###########################
15 while read a
16 do
17     echo $a
18 done < a.txt 

 1 # 读文件已空格分隔
 2 w=`awk -F ":" ‘{print $1}‘ c`
 3 for d in $w
 4 do
 5     $d
 6 done
 7 ###########################
 8 for ((i=0;i<${#o[*]};i++))
 9 do
10 echo ${o[$i]}
11 done

1 #  当command不为0时循环
2 until command   
3 do
4     body
5 done

1 break N     #  跳出几层循环
2 continue N  #  跳出几层循环，循环次数不变
3 continue    #  重新循环次数不变