shell(二)-JZTXT

1、case语句

[root@localhost day1121]# cat test1.sh
#!/bin/bash
case $1 in 
"1")
    echo "您输入的是1"
;;
"2")
    echo "您输入的是2"
;;
*)
    echo "您输入的是其他"
;;
esac
[root@localhost day1121]# bash test1.sh
您输入的是其他
[root@localhost day1121]# bash test1.sh 1
您输入的是1
[root@localhost day1121]#

案例: 判断⽤户输⼊的字符类型使⽤case,字母类型[a-z][A-Z] 数字类型[0-9] 其他

[root@localhost day1121]# cat test2.sh
#!/bin/bash
read -p "请输入任意一个字符" ch
case $ch in
[A-Z] | [a-z])
    echo "字母"
;;
[0-9])
    echo "数字"
;;
*)
    echo "其他"
;;
esac
[root@localhost day1121]# bash test2.sh
请输入任意一个字符a
字母
[root@localhost day1121]# bash test2.sh
请输入任意一个字符1
数字
[root@localhost day1121]# bash test2.sh
请输入任意一个字符/
其他
[root@localhost day1121]#

2、循环语句

for 变量 in 空格分隔的数据列表;do 语句块 done

[root@localhost day1121]# cat test3.sh
#!/bin/bash
for i in 1 2 3 4 5
do
    echo $i
done
[root@localhost day1121]# bash test3.sh
1
2
3
4
5
[root@localhost day1121]# cat test4.sh
#!/bin/bash
for i in $*
do
    echo $i
done
[root@localhost day1121]# bash test4.sh
[root@localhost day1121]# bash test4.sh
[root@localhost day1121]# bash test4.sh aa bb cc
aa
bb
cc
[root@localhost day1121]#

for 变量 in {起始值..终⽌值..步进值};do 语句块 done

[root@localhost day1121]# cat test5.sh
#!/bin/bash
for i in {1..5..1}
do
    echo $i
done
[root@localhost day1121]# bash test5.sh
1
2
3
4
5
[root@localhost day1121]# cat test6.sh
#!/bin/bash
for i in {101..105..1}
do
    echo hadop$i
done

[root@localhost day1121]# bash test6.sh
hadop101
hadop102
hadop103
hadop104
hadop105
[root@localhost day1121]# cat test7.sh
#!/bin/bash
for i in hadop{101..105}
do
    echo $i
done

[root@localhost day1121]# bash test7.sh
hadop101
hadop102
hadop103
hadop104
hadop105
[root@localhost day1121]#

for (( 初始值; 条件判断; 步进值 )) ;do 语句块 done

[root@localhost day1121]# cat test8.sh
#!/bin/bash
for ((i=1;i<=5;i++))
do
    echo $i
done
[root@localhost day1121]# bash test8.sh
1
2
3
4
5
[root@localhost day1121]#

while循环

初始计数器 while [ 计数器判断 ] do 语句块计数器步进done

[root@localhost day1121]# cat test9.sh
#!/bin/bash
i=1
while [ $i -le 5 ]
do
    echo $i
    let i=i+1
done
[root@localhost day1121]# bash test9.sh
1
2
3
4
5
[root@localhost day1121]#

break 退出循环 , continue 重新进⼊下次循环

[root@localhost day1121]# cat test10.sh
#!/bin/bash
#break continue
i=1
while [ $i -le 10 ]
do
    echo $i
    let i=i+1
    if [ $i -eq 6 ]
    then 
        break
    fi
done
[root@localhost day1121]# bash test10.sh
1
2
3
4
5
[root@localhost day1121]#

[root@localhost day1121]# cat test11.sh
#!/bin/bash
#break continue
i=0
while [ $i -lt 10 ]
do
    let i=i+1
    if [ $i -eq 7 ]
    then 
        continue
    fi
    echo $i
done
[root@localhost day1121]# bash test11.sh
1
2
3
4
5
6
8
9
10
[root@localhost day1121]#

until 否定 while

#!/bin/bash
i=1
until [ $1 -ge 5 ]
do
    echo $i
    let i=i+1
done

练习: 求1-100的和

[root@localhost day1121]# cat test13.sh
#!/bin/bash
sum=o
for ((i=1;i<=100;i++))
do
    let sum=i+sum
done
echo "1+2+3+...+100=${sum}"
[root@localhost day1121]# bash test13.sh
1+2+3+...+100=5050
[root@localhost day1121]#

练习 99乘法表

[root@localhost day1121]# cat test14.sh
#!/bin/bash
for ((i=1;i<=9;i++))
do
    for ((j=1;j<=i;j++))
    do
        echo -ne "$i*$j=$((i*j))\t"
    done
    echo
done
[root@localhost day1121]# bash test14.sh
1*1=1    
2*1=2    2*2=4    
3*1=3    3*2=6    3*3=9    
4*1=4    4*2=8    4*3=12    4*4=16    
5*1=5    5*2=10    5*3=15    5*4=20    5*5=25    
6*1=6    6*2=12    6*3=18    6*4=24    6*5=30    6*6=36    
7*1=7    7*2=14    7*3=21    7*4=28    7*5=35    7*6=42    7*7=49    
8*1=8    8*2=16    8*3=24    8*4=32    8*5=40    8*6=48    8*7=56    8*8=64    
9*1=9    9*2=18    9*3=27    9*4=36    9*5=45    9*6=54    9*7=63    9*8=72    9*9=81    
[root@localhost day1121]#