入门级shell脚本编程实例

相信大家对Linux Shell脚本并不陌生，在本文为您仔细讲解Shell脚本编程入门例子的相关知识和一些Code实例。

例子一：绘制特殊图形

#!/bin/bash
MAX_NO=0
echo -n "Enter Number between (5 to 9) : "
 read MAX_NO 
if ! [ $MAX_NO -ge 5 -a $MAX_NO -le 9 ] ; then
 echo "WTF... I ask to enter number between 5 and 9, Try Again"
 exit 1
 fi 
clear 
for (( i=1; i=i; s-- ))
 do
 echo -n " "
 done
 for (( j=1; j=1; i-- ))
 do
 for (( s=i; s<=MAX_NO; s++ ))
 do
 echo -n " "
 done
 for (( j=1; j<=i; j++ ))
 do
 echo -n " ."
 done
 echo ""
 done
echo -e "\n\n\t\t\t Whenever you need help, Tecmint.com is always there"

你应该不会被上述例子中的“关键字”困扰了，很多都是你熟悉的，或者从它们的名字可以猜出它们的意思，如“max”设定某个变量的最大值，“for”是一个循环。

输出结果：

[root@tecmint ~]# chmod 755 Special_Pattern.sh
[root@tecmint ~]# ./Special_Pattern.sh
Enter Number between (5 to 9) : 6
       .
      . .
     . . .
    . . . .
   . . . . .
  . . . . . .
  . . . . . .
   . . . . .
    . . . .
     . . .
      . .
       .
 
        Whenever you need help, Tecmint.com is always there

如果你有其它语言的编程基础，那么学习上面的脚本对你来说应该很容易。即使你是计算机方面的新手，这个学习过程也不会太难。

例子二：五颜六色的脚本

Linux终端也是支持五颜六色的，请看下面的脚本：

#!/bin/bash 
clear
echo -e "\033[1m Hello World"
 # bold effect
echo -e "\033[5m Blink"
       # blink effect
echo -e "\033[0m Hello World"
 # back to noraml 
echo -e "\033[31m Hello World"
 # Red color
echo -e "\033[32m Hello World"
 # Green color
echo -e "\033[33m Hello World"
 # See remaing on screen
echo -e "\033[34m Hello World"
echo -e "\033[35m Hello World"
echo -e "\033[36m Hello World" 
echo -e -n "\033[0m"
  # back to noraml
echo -e "\033[41m Hello World"
echo -e "\033[42m Hello World"
echo -e "\033[43m Hello World"
echo -e "\033[44m Hello World"
echo -e "\033[45m Hello World"
echo -e "\033[46m Hello World" 
echo -e "\033[0m Hello World"

输出结果：

你可以对上面的列子举一反三，把它用到你自己的脚本中去。

例子三：加密文件/目录

下面的例子演示了如何加密一个份文件或者文件夹。目前的这个版本的脚本有一些局限，例如你必须把它和你要加密的文件/目录放到同一个文件夹下面。另外，你可能需要安装“pinentry-gui”。在Fedora下安装“pinentry-gui”的命令是：

[root@midstage ~]# yum install pinentry-gui

在Ubuntu/Debian下安装“pinentry-gui”的命令是：

[root@midstage ~]# apt-get install pinentry-gui

创建一个脚本“Encrypt.sh”，将下面的代码复制进去。你也可以从这里下载这个脚本。

#!/bin/bash
echo "Welcome, I am ready to encrypt a file/folder for you"
echo "currently I have a limitation, Place me to the same folder,
where a file to be encrypted is present"
echo "Enter the Exact File Name with extension"
read file;
gpg -c $file
echo "I have encrypted the file sucessfully..."
echo "Now I will be removing the original file"
rm -rf $file

输出结果：

[root@tecmint ~]# chmod 755 Encrypt.sh
[root@tecmint ~]# ./Encrypt.sh
Welcome, I am ready to encrypt a file/folder for you
currently I have a limitation, Place me to the same folder,
where a file to be encrypted is present
Enter the Exact File Name with extension 
package.xml 
                   Enter passphrase 
                   Passphrase _________________________________  
                   Please re-enter this passphrase 
                   Passphrase _________________________________  
I have encrypted the file successfully...
Now I will be removing the original file

代码说明：

gpg -c: 这个命令使用aka来加密文件。 在你需要的时候，你需要对加密的文件进行解密。这里我们不给出具体的代码了，你可以自己尝试着写出来。提示：使用命令 gpg -d filename.gpg > filename 可以解密一份文件。

例子四：查看服务器利用率

查看服务器的利用率是管理员的一份重要的日常工作。聪明的管理员是知道如何是这份任务自动化的。

#!/bin/bash
date;
echo "uptime:"
uptime
echo "Currently connected:"
w
echo "--------------------"
echo "Last logins:"
last -a |head -3
echo "--------------------"
echo "Disk and memory usage:"
df -h | xargs | awk '{print "Free/total disk: " $11 " / " $9}'
free -m | xargs | awk '{print "Free/total memory: " $17 " / " $8 " MB"}'
echo "--------------------"
start_log=`head -1 /var/log/messages |cut -c 1-12`
oom=`grep -ci kill /var/log/messages`
echo -n "OOM errors since $start_log :" $oom
echo ""
echo "--------------------"
echo "Utilization and most expensive processes:"
top -b |head -3
echo
top -b |head -10 |tail -4
echo "--------------------"
echo "Open TCP ports:"
nmap -p- -T4 127.0.0.1
echo "--------------------"
echo "Current connections:"
ss -s
echo "--------------------"
echo "processes:"
ps auxf --width=200
echo "--------------------"
echo "vmstat:"
vmstat 1 5

输出结果：

[root@tecmint ~]# chmod 755 Server-Health.sh
[root@tecmint ~]# ./Server-Health.sh
Tue Jul 16 22:01:06 IST 2013
uptime:
22:01:06 up 174 days, 4:42, 1 user, load average: 0.36, 0.25, 0.18
Currently connected:
22:01:06 up 174 days, 4:42, 1 user, load average: 0.36, 0.25, 0.18
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
tecmint pts/0 116.72.134.162 21:48 0.00s 0.03s 0.03s sshd: tecmint [priv]
--------------------
Last logins:
tecmint pts/0 Tue Jul 16 21:48 still logged in 116.72.134.162
tecmint pts/0 Tue Jul 16 21:24 - 21:43 (00:19) 116.72.134.162
--------------------
Disk and memory usage:
Free/total disk: 292G / 457G
Free/total memory: 3510 / 3838 MB
--------------------
OOM errors since Jul 14 03:37 : 0
--------------------
Utilization and most expensive processes:
top - 22:01:07 up 174 days, 4:42, 1 user, load average: 0.36, 0.25, 0.18
Tasks: 149 total, 1 running, 148 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.1%us, 0.0%sy, 0.0%ni, 99.3%id, 0.6%wa, 0.0%hi, 0.0%si, 0.0%st
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 3788 1128 932 S 0.0 0.0 0:32.94 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 0:14.07 migration/0

例子五：查看硬盘使用情况及发送提示邮件

下面的这个例子展示了当硬盘的使用空间超出了预期设定的值时，如果通过脚本来发送提示邮件。

MAX=95
[email protected]
PART=sda1 
USE=`df -h |grep $PART | awk '{ print $5 }' | cut -d'%' -f1`
if [ $USE -gt $MAX ]; then
echo "Percent used: $USE" | mail -s "Running out of disk space" $EMAIL
fi

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