5个Shell脚本编程入门练习例子

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。下面的这份脚本会抓取服务器的很多信息，快快试试吧！

#!/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=server@127.0.0.1
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

说明：将上述脚本中的“user”替换成你的用户名。你可以通过命令“mail”来查看你的邮件。