shell编程之基础语法

基本语法包含：定义，变量，命令，if语句，循环语句。学会这么多，就能基本做基本shell编程喽

下面为shell编程几个小demo，可研究学习

1、文件判断

#!/bin/bash
echo "input a file name:"
read file_name
if [ -d $file_name ] ; then
echo " $file_name is a dir"
elif [ -f $file_name ] ; then
echo " $file_name is file"
elif [ -c $file_name -o -b $file_name] ; then
echo " $file_name is a devicefile"
else
echo " $file_name is an unknowfile "
fi

 #!/bin/bash
read a,b,c
value1=`expr $a + $b + $c`
echo "The value of value1 is $value1"
value2=`expr $c / $b`
echo "The value of value2 is $value2"
value3=`expr $c \* $b`    #整除
echo "The value of value3 is $value3"
value4=`expr $a + $c / $b`
echo "The value of value4 is $value4"