Shell 语句

Posted 2020-09-21 皖心

一 test 测试：

测试命令 test [ ] [[ ]] (( ))
打开man test 逐一介绍每个参数

 

浮点计算：echo \'scale=2;1/3\'|bc -l
 

测试操作
命令执行后会返回到一个系统变量中 $?
如果$?值为0 表示命令执行成功 否则为失败

二流程控制： if   while   for

#!/bin/bash
read -p \'please input username:\' usr
read -p \'please input passwd:\' passwd

if [ $usr = \'alex\' -a $passwd = \'alex3714\' ];then
   echo \'login successful\'
else
   echo \'username or password is worng\'
fi

用户测试

!/bin/bash
age=57
while :
do

read -p \'input oldboy age:\' ag

if [ $ag -eq $age ];then
    echo "bingo"
    break
elif [ $ag -gt $age ];then
    echo "the age is older"
else
    echo "the age is younger"
fi

  if [ -z $ag ];then
  continue
  fi

done

猜年龄

#!/bin/bash
read -p \'please input your score:\' score

if [ $score -ge 90 ];then
  echo \'excellent\'
elif [ $score -ge 70 -a $score -lt 90 ];then
  echo \'good\'
elif [ $score -ge 60 -a $score -lt 70];then
  ehco \'not bad\'
else
  echo \'bad\'
fi

成绩查询

#!/bin/bash
read -p \'input your file:  \' file
if [ -p $file ];then
   echo "$file is block file"
elif [ -f $file ];then
   echo "$file is reuler file"
elif [ -d $file ];then
   echo "$file is directory file"
else
   echo "$file is unkown"
fi

测文件类型

#!/bin/bash
for ((i =1;i<=9;i++))
do
   for ((j=1;j<=i;j++))
   do
     echo -n "$i*$j=$[$i*$j] "
   done
echo
done

九九乘法表

#!/bin/bash
usr=\'mona\'
passwd=\'123\'
tag=true
while $tag
do
  read -p \'please input your name: \' name
  read -p \'please input your password: \' pd
  if [ $name = $usr ] && [ $pd = $passwd ];then
  echo \'login successful\'
    while $tag
    do
       read -p \'input your indirction: \' cmd
       if [ $cmd = \'quit\' ];then
        tag=false
       else
           $cmd
        fi
    done
  fi
done

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