shell基础2

15-06-23 来源：[db:作者]

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各种引号的用法总结如下

1、单引号 ‘

由单引号括起来的字符都作为普通字符出现。特殊字符用单引号括起来以后，也会失去原有意义，而只作为普通字符解释。

2、双引号 “

由双引号括起来的字符，除、\、′、和”这几个字符仍是特殊字符并保留其特殊功能外，其余字符仍作为普通字符对待。对于来说，就是用其后指定的变量的值来代替这个变量和；对于而言，是转义字符，它告诉shell不要对其后面的那个字符进行特殊处理，只当作普通字符即可。可以想见，在双引号中需要在前面加上的只有四个字符，，’和”本身。而对”号，若其前面没有加，则Shell会将它同前一个”号匹配。

3、反引号 `

反引号（`）这个字符所对应的键一般位于键盘的左上角，不要将其同单引号（’）混淆。反引号括起来的字符串被shell解释为命令行，在执行时，shell首先执行该命令行，并以它的标准输出结果取代整个反引号（包括两个反引号）部分。

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

if [ "$1" = "hello" ]; then
        echo "hello, who are you?"
elif [ "$1" = "" ]; then
        echo "you must input parameters,ex>{$0 somewprd}"
else
        echo  "the only parameter is 'hello',ex>{$0 hello}"
fi
~

可以进行空字符串的比较 == "",这里的{} 只是一个字符

netstat -tuln 127.0.0.1 表示仅对本机开放 0.0.0.0 或者:::: 表示对整个internet开放

不能运行，尝试的例子
#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

netstat_list=$(netstat -tuln)

if [ $($netstat%":80") ]; then
        echo ":80"
fi

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

testing=$(netstat -tuln | grep ":80")  #$() 命令行之前没有空格
if [ "$testing" != "" ]; then
        echo "www is running in your system"
fi
testing=$( netstat -tuln | grep ":22" )   #$() 命令行之前可以有空格
if [ "$testing" != "" ]; then
        echo " ssh is running in your system"
fi
~

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

read -p "please input your time:" lasttime
nowtime=$( date +%s )
lasttime=$( date --date "$lasttime" +%s )
echo $[[$lasttime-$nowtime ]]
exit 0

为什么输出来是个这了，没有进行减法操作（当作了字符串？？？还是(())   ）
fuhui@ubuntu:~/script$ sh sh13.sh 
please input your time:20150902
$[[1441177200-1434859352 ]]

正则匹配的测试
fuhui@ubuntu:~/script$ echo 1234 | grep "[0-9]\{3\}"
1234

在{}需要进行转码，没有//这样的标志

1 declare -i number 2 # 脚本余下的部分会把”number”当作整数看待.

   #!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

read -p "please input your time: ex(20100101)" lasttime

date_d=$( echo $lasttime | grep '[0-9]\{8\}')  #重点学习一下正则的匹配

if [ "$date_d" = "" ]; then
        echo "you input wrong date format.."
        exit 1
fi
declare -i date_dem=`date --date="$date_d" +%s`
declare -i date_new=$( date +%s )
declare -i date_total=$(($date_dem-$date_new))
declare -i date_day=$(($date_total/60/60/24))

if [ $date_day -lt 0 ]; then
        echo "you had been demobilization before $((-1*$date_day))"
fi
~

出现了一个错误，如下所示： fuhui@ubuntu:~/script$ sh sh13.sh please input your time: ex(20100101)20110505 sh13.sh: 13: sh13.sh: declare: not found sh13.sh: 14: sh13.sh: declare: not found

修改了文件属性如下，错误就没有了 chmod +x sh13.sh

case语句

case $变量名称 in <==关键词为 case ，相当于switch的变量 “第一个变量内容”) <==每个变量内容建议用双引号括起来，关键词则为小括号 ) 程序段 ;; <==操作结尾使用两个连续的分号来处理！ “第二个发量内容”) 程序段 ;; ) <==最后一个变量内容都会用来代表所有其他值类似于default语句，结尾有;;符 ;; esac <==最终的 case 结尾，case的反向书写形式

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

case $1 in
"hello")
        echo "continue to do "
        ;;
"")
        echo "you should input a option"
        ;;
*)
        echo "you must input parameter,ex >$0,someoption"
        ;;
esac


fuhui@ubuntu:~/script$ sh sh15.sh 3
you must input parameter,ex >sh15.sh,someoption
fuhui@ubuntu:~/script$ sh sh15.sh hello       #输入"hello"和hello居然是一样的
continue to do 
fuhui@ubuntu:~/script$ sh sh15.sh "hello"
continue to do

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

read -p "input one of ont, two, three:" valu

case $valu in
        "one")
                echo "first"
                ;;
        "two")
                echo "second"
                ;;
        "three")
                echo "third"
                ;;
        *)
                echo "error"
                ;;
esac

函数声明必须在shell的最前面 function funName{ }

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

function prifxit(){
        echo -n "you choice is: "
}
read -p "input one of ont, two, three:" valu

case $valu in
        "one")
                prifxit; echo "first"
                ;;
        "two")
                prifxit; echo "second"
                ;;
        "three")
                prifxit; echo "third"
                ;;
        *)
                prifxit; echo "error" | tr 'a-z' 'A-Z'   #特别注意大小写的转换
                ;;
esac

特别注意：sh sh17.sh不能运行，提示错误。这时候修改文件为可执行，就没有错误了。（虽然不知道为什么）
cp操作会复制文件的权限

fuhui@ubuntu:~/script$ chmod +x sh17.sh 
fuhui@ubuntu:~/script$ ./sh17.sh 
input one of ont, two, three:one
you choice is: first
fuhui@ubuntu:~/script$ ./sh17.sh 
input one of ont, two, three:ss
you choice is: ERROR

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

function prifxit(){
        echo -n "the function name $0 : $1"
}
read -p "input one of ont, two, three:" valu

case $valu in
        "one")
                prifxit "fuhui"; echo "first"
                ;;
        "two")
                prifxit "hui"; echo "second"
                ;;
        "three")
                prifxit "do"; echo "third"
                ;;
        *)
                prifxit "it"; echo "error" | tr 'a-z' 'A-Z'
                ;;
esac

函数的例子，函数内的$0并没有指明这个函数的名字，而是执行脚本的名称。
注意：函数的$1代表函数的第一个参数，依次类推
fuhui@ubuntu:~/script$ ./sh18.sh 
input one of ont, two, three:
the function name ./sh18.sh : itERROR
fuhui@ubuntu:~/script$ ./sh18.sh 
input one of ont, two, three:one
the function name ./sh18.sh : fuhuifirst


while [ condition ] <==中括号内为判断式
do <==do 循环的开始！
程序段落
done <==done 循环的结束


until [ condition ]
do
程序段落
done

两个循环中值得条件不一样，正好相反。

#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

while [ "$yn" != "yes" -a "$yn" != "YES" ]        #特别注意-a是&&的意思，-o是||的意思 ，支持 !=
do
        read -p "please input a option :" yn
done
echo "you option is right"

until的用法，注意准换大小写的用法

V=hello
V=`echo $V | tr '[:lower:]' '[:upper:]'`
echo $V


下面的转化效果是一样的
echo as | tr '[:lower:]' '[:upper:]'
echo as | tr [:lower:] [:upper:]


#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

until [ "$yn" = "YES" ]
do
        read -p "please input a option :" yn
        yn=$(echo $yn | tr 'a-z' 'A-Z')
        if [ "$yn" = "EXIT" ]; then
                echo "exit program"
                break;
        fi
done

计算1+2+。。。+100

declare -i num=0
done
#!/bin/bash
# program:test example 01
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export PATH

declare -i sum=0
declare -i num=0

while [ $num -le 100 ]		#特别注意 -le 平时使用的时候都是 test $num -le 100 
do      
        sum=$(($sum+$num))  #需要注意$sum 和sum的区别
        num=$(($num+1))
done
echo  "the sum is: $sum"
exit 0
~
echo "you option is right"

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