【Linux shell】条件判断和流程控制

#!/bin/bash
read a
read b
num1=$((a + b))
echo "和为$num1"num2=$((a * b))
echo "积为$num2"

​

#!/bin/bash
read num
if [ $num -lt 25 ];thenecho "$num is smaller than 25"
elif [ $num -eq 25 ];thenecho "$num is equal 25"
elif [ $num -gt 25 ];thenecho "$num is bigger than 25"
fi

​

#!/bin/bash
echo $1
if [ -r $1 ];thenecho "the file has the access of read"
fi
if [ -w $1 ];thenecho "the file has the access of write"
fi
if [ -x $1 ];thenecho "the file has the access of execute"
fi

​

#!/bin/bash
echo $1
if [ -f $1 ];thenecho "文件存在并且是一个常规的文件"
fi
if [ -e $1 ];thenecho "文件存在"
fi
if [ -d $1 ];thenecho "文件存在并且是一个目录"
fi

​

if [ 条件 ];then#要执行的代码
elif [ 条件 ];then#要执行的代码
else #要执行的代码
fi

#!/bin/bash
for ((i=1;i<5;i++));doecho "current number is $i"
done

​

for i in "$@";doecho "arg is $i"
done

​

p=("zhangsan" "lisi" "wangwu")
for i in "${p[@]}";doecho "$i"
done

​

while[ 条件 ];do#循环体
done

echo "please input a number"
read num
aim=24
while true;doif [ $num -lt $aim ];thenecho "the number you guess is smaller"read numelif [ $num -gt $aim ];thenecho "the number you guess is bigger"read numelif [ $num -eq $aim ];thenecho "you are right"breakfi
done

​

case 值 in
1)echo "选择1";;
2)echo "选择2";;
3)echo "选择3";;
*)echo "无效选择";;
esac

read choice
case $choice in
1)echo "选择功能1";;
2)echo "选择功能2";;
3)echo "选择功能3";;
*)echo "无效选择";;
esac

​

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