一、if语句
语句格式:
if 条件
then
elif 条件
then
else
fi
#!/bin/bash
echo -n "Please enter your name:"
read NAME
echo if [ -z $NAME ]
echo $NAME
if [ -z $NAME ] || [ "$NAME"="" ];then
echo "You didn't enter your name"
elif [ "$NAME"="root" ];then
echo "root"
elif [ "$NAME"="shell" ]; then
echo "shell"
else
echo "Hello,$NAME"
fi
二、case语句为多选择语句,可以匹配一个值或者一个模式。
case 值 in
模式1)
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命令1
;;
模式2)
命令2
;;
esac
#!/bin/bash
#case语句示例
echo "请输入A,B,C,中的任意一个字符:"
read grade
case $grade in
"A")
echo "You enter A"
;;
"B")
echo "You enter B"
;;
"C")
echo "You enter C"
;;
*)
echo "Bad input"
exit
;;
esac
三、for语句
for 变量名 in 列表
do
命令1
命令n
done
#!/bin/bash
#for语句的示例
for loop in 1,2,3,4,5
do
echo $loop
done
for loop in "Hello World"
do
echo $loop
done
for loop in `cat myfile`
do
echo $loop
done
四、until语句
until 条件
do
命令
done
五、while语句
while 条件
do
done
#!/bin/bash
echo "while语句示例"
echo "CTRL+D is means exit"
while echo "Hello world!" ;read name
do
echo "yeah!!! $name"
done
# 循环读入文件内容
while read line
do
echo $line
done < name.txt
六、continue :跳出本次循环继续下一次,break :跳出真个循环 break后面可接参数 n,表示跳出几层循环
#!/bin/bash
for num in 1 2 3 4 5 6 7 8 9
do
echo $num
if [ "$num" = "3" ]
then
echo "Continue=="
continue
fi
if [ "$num" = "7" ]
then
break
fi
done