【Linux入门到精通系列讲解】shell脚本语法入门教程（看一篇就够了）

文章目录

• 1 IF
• 2 IF-TEHN-ELSE
• 3 多步判断
• 4 FOR循环
• 5 WHILE循环
• 6 case语句
• 7 函数控制

1 IF

#!/bin/bash
#假如在/tep/abc文件夹 那么创建一个

if [ ! -d ~/Desktop/work/tmp ]
   then
      mkdir -v ~/Desktop/work/tmp
      echo "123"
      echo "create /tmp/abc ok"
fi

2 IF-TEHN-ELSE

#!/bin/bash

if [ $USER == 'root' ]
    then 
        echo "hello,root"
else
    echo "hello,guest"
fi         

3 多步判断

#!/bin/bash

if [ $1 -eq $2 ]
        then
                echo "$1==$2"
else
        if [ $1 -gt $2 ]
                then
                        echo "$1>$2"
        else
                        echo "$1<$2"
        fi
fi
~                                                                               
~           

#!/bin/bash

if [ $1 -eq $2 ]
        then
                echo "$1==$2"
elif [ $1 -gt $2 ]
        then
                echo "$1>$2"
else
        echo "$1<$2"
fi
~                                                                               
~                  

数学表达式-双括号

#!/bin/bash

if (( 100%3+1>1 ));
    then
        echo "yes"
else
    echo "no"
fi

双方括号可以做通配符。

#!/bin/bash

for var in ab ac rx bx rvv vt
        do
                if [[ "$var" == r* ]]
                        then
                                echo "$var"
                fi
done
~                                                                               
~                                                                               
~                         

4 FOR循环

#/bin/bash
for var in `seq 1 9`
    do
        echo $var
        sleep 1
done
    

#!/bin/bash

for (( i=1;i<10;i++ ))
    do
        echo $i
done

5 WHILE循环

#!/bin/bash

read -p "NUM:" num1
while [ $num1 -gt 0 ]
    do
        echo ">"
        sleep 3
done

6 case语句

#!/bin/bash

read -p "num:" n

case $n in
1)
    echo haha
;;
2)
    echo hehe
;;
*)
    echo "1|2"
;;
esac

7 函数控制

##########################################################################
# File Name: do11.sh
# Author: LiXiang
# mail: [email protected]
# Created Time: Wed 24 Mar 2021 08:18:44 PM CST
#########################################################################
#!/bin/bash

start(){
    echo "Apache start...."
}

stop(){
    echo "Apache stop....."
}


start