#!/bin/bash
read -p "enter a number: " number  #提示用户输入数字
if [ -z $number ];then             #判断用户是否输入，如果未输入则打印error
  echo "Error"
  exit
else
  jieguo=`echo "$number*1" | bc `  #把用户的输入值和1相乘，交给bc做运算
  if [ $jieguo -eq 0 ];then          #判断计算结果是否为0，为0则说明number非数字(字符串和0相乘结果为0)
   echo "not a number"
   exit
  fi
fi

read -p "input a word :" word
if [ ! -n "$word" ] ;then
  echo "you have not input a word!"
else
  echo "the word you input is $word"
fi

#!/bin/bash
if [ ! -n "$1" ] ;then
  echo "you have not input a word!"
else
  echo "the word you input is $1"
fi

#!/bin/sh
para1=
if [ ! $para1 ]; then
 echo "IS NULL"
else
 echo "NOT NULL"
fi

#!/bin/sh
dmin=
if test -z "$dmin"
then
 echo "dmin is not set!"
else 
 echo "dmin is set !"
fi

#!/bin/sh 
dmin=
if [ "$dmin" = "" ]
then
 echo "dmin is not set!"
else 
 echo "dmin is set !"
fi

#! /bin/bash
echo "Input Param Is [$1]"
if [ ! -n "$1" ] ;then
 echo "you have not input a null word!"
 ./app1;./app12;./app123
elif [ $1 -eq 2 ];then
 ./app12;./app123
elif [ $1 -eq 90 ];then
 echo "yy";
fi