一、判断语句
1、if……then……if语句
#!/bin/bash
read -p "请输入y/n:" ym
if [ "$ym" == "Y" -o "$ym" == "y" ]; then
echo "你输入的是Y"
exit 0
elif [ "$ym" == "N" -o "$ym" == "n" ]; then
echo "你输入的是N"
exit 0
else
echo "你输入的不是N或者Y"
fi
note：if附近很多空格，全部用空格隔开
2、case……esac语句
#!/bin/bash
read -p "请输入（Y/n）:" fei
case $fei in
y)
echo '您输入的是y'
;;
Y)
echo '您输入的是Y'
;;
n)
echo '您输入的是n'
;;
N)
echo '您输入的是N'
;;
*)
echo '您输入的不符合要求'
;;
esac
二、循环语句
1、while语句
#!/bin/bash
s=0
i=0
while [ "$i" != 100 ]
do
i=$(($i+1))
s=$(($s+$i))
done
echo "the result of '1+2+……+100' is $s"
2、until语句
#!/bin/bash
until [ "$yn" == "yes" -o "$yn" == "YES" ]
do
read -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."
note：当until满足是进入循环，和while相反
3、for…do…done语句
#举例一
#!/bin/bash
for var in xi fen fei
do
echo "this is ${var} "
done
#举例二
#!/bin/bash
filelist=$(ls -la)
for var in v$filelist
do
echo "${var}"
done
#举例三
#!/bin/bash
s=0
for i in $(seq 1 100)
do
s=$(($s+$i))
done
echo "the result of '1+2+……+100' is $s"
#举例四
#!/bin/bash
echo "请输入从1开始累加到N的值："
read nu
s=0
for((i=1;i<=$nu;i=i+1))
do
s=$(($s+$i))
done
echo "1+……+$nu is ==>$s"
