浅谈Shell脚本参数与交互及常见问题

[root@localhost 20190105]# vi paral.sh
#!/bin/bash
#显示脚本名
echo 'The script name is '$0
#显示第1个参数
echo 'The 1th parameter is '$1
#显示第2个参数
echo 'The 2th parameter is '$2
#显示第3个参数
echo 'The 3th parameter is '$3
#显示第4个参数
echo 'The 4th parameter is '$4
#显示第5个参数
echo 'The 5th parameter is '$5
#显示第6个参数
echo 'The 6th parameter is '$6
#显示第7个参数
echo 'The 7th parameter is '$7
#显示第8个参数
echo 'The 8th parameter is '$8
#显示第9个参数
echo 'The 9th parameter is '$9
[root@localhost 20190105]# ./paral.sh Ni hao , Nice to meet you !
The script name is ./paral.sh
The 1th parameter is Ni
The 2th parameter is hao
The 3th parameter is ,
The 4th parameter is Nice
The 5th parameter is to
The 6th parameter is meet
The 7th parameter is you
The 8th parameter is !
The 9th parameter is      //空值
[root@localhost 20190105]#

read 变量1 [变量2...]

[root@localhost 20190105]# vi read1.sh
#!/bin/bash
#初始化变量的值
input1=''                                               #设置 input1 变量值为空
input2=''                                               #设置 input2 变量值为空
input3=''                                               #设置 input3 变量值为空
input4=''                                               #设置 input4 变量值为空
#until 循环，当 input1 变量的值为 exit 时退出该循环
until [ "$input1" = exit ]
do
       echo 'Please input the values:'
#读取键盘输入的数据
       read input1 input2 input3 input4
#输入的不是 exit 时把用户输入的数据显示在屏幕上
       if [ "$input1" != exit ]
       then
               echo 'input1: '$input1                  #输出变量 input1 的值
               echo 'input2: '$input2                  #输出变量 input2 的值
               echo 'input3: '$input3                  #输出变量 input3 的值
               echo 'input4: '$input4                  #输出变量 input4 的值
               echo
#当输入为 exit 时显示退出脚本的提示
       else
               echo 'Exit the script.'
       fi
done
[root@localhost 20190105]# chmod +x read1.sh
[root@localhost 20190105]# ./read1.sh
Please input the values:
How do you do           //输入的数据个数与变量个数相等
input1: How
input2: do
input3: you
input4: do

Please input the values:
Welcome to beijing       //输入的数据个数小于变量个数
input1: Welcome
input2: to
input3: beijing
input4:

Please input the values:
let's go              //输入的数据个数小于变量个数
input1: let's
input2: go
input3:
input4:

Please input the values:
Nice to meet you,too!      //输入的数据个数大于变量个数
input1: Nice
input2: to
input3: meet
input4: you,too!

Please input the values:    //结束程序
exit
Exit the script.
[root@localhost 20190105]#

[root@localhost 20190105]# vi vall.sh
#!/bin/bash
echo 'The value of $# is: '$#           //输出$#变量的值
echo 'The value of $* is: '$*           //输出$*变量的值
echo 'The value of $@ is: '$@           //输出$@变量的值
echo 'The value of $$ is: '$$           //输出$$变量的值
echo 'The value of $! is: '$!           //输出$!变量的值
echo 'The value of $- is: '$-           //输出$-变量的值
echo 'The value of $? is: '$?           //输出$?变量的值
[root@localhost 20190105]# ./vall.sh how do you do
The value of $# is: 4 //输出4变量的值
The value of $* is: how do you do //输出how do you do变量的值
The value of $@ is: how do you do //输出how do you do变量的值
The value of $$ is: 9040 //输出9040变量的值
The value of $! is:  //输出变量的值
The value of $- is: hB //输出hB变量的值
The value of $? is: 0 //输出0变量的值
[root@localhost 20190105]#

命令 > /dev/null

命令 2> /dev/null

命令 > /dev/null 2> /dev/null

if grep jack /etc/passwd > /dev/null
then
 echo "jack found"
fi

[root@localhost ~]# ps -ef | grep sshd | awk '{print $2}'
4478
12821
22028

[root@localhost ~]# ps -ef | \
> grep ssh | \
> awk '{print $2}'
4478
12821
23375
[root@localhost ~]#