第十三章、學習 Shell Scripts - for Fedora Core 4

1. 如同前面 bash command 提到的，指令與參數間的多個空白會被忽略掉；
2. 而空白行也將被忽略掉！，並且 [tab] 也是不會被理會的！
3. 如果讀取到一個 Enter 符號 ( CR )），就嘗試開始執行該行命令；
4. 至於如果一行的內容太多，則可以使用 \[Enter] 來延伸至下一行；
5. 此外，使用最多的 # 可做為註解！任何加在 # 後面的字，將全部被視為註解文字而被忽略！

• 將 shell.sh 加上可讀與執行 (rx) 的權限，然後就能夠以 ./shell.sh 來執行了；
• 直接以 sh shell.sh 的方式來直接執行即可。

[root@linux ~]# mkdir scripts; cd scripts
[root@linux scripts]# vi sh01.sh
#!/bin/bash
# Program:
#       This program is used to show "Hello World !" in screen.
# History:
# 2005/08/23	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
echo -e "Hello World ! \a \n"
exit 0

[root@linux scripts]# sh sh01.sh
Hello World !

• script 的功能；
• script 的版本資訊；
• script 的作者與聯絡方式；
• script 的版權宣告方式；
• script 的 History (歷史紀錄)；
• script 內較特殊的指令，使用絕對路徑的方式來下達；
• script 運作時需要的環境變數預先宣告與設定。

[root@linux scripts]# vi sh02.sh
#!/bin/bash
# Program:
# 	Let user keyin their first and last name, and show their full name.
# History:
# 2005/08/23	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

read -p "Please input your first name: " firstname
read -p "Please input your last name:  " lastname
echo -e "\nYour full name is: $firstname $lastname"

[root@linux scripts]# vi sh03.sh
#!/bin/bash
# Program:
# 	User can keyin filename to touch 3 new files.
# History:
# 2005/08/23	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

# 1. 讓使用者輸入檔案名稱，並取得 fileuser 這個變數；
echo -e "I will use 'touch' command to create 3 files."
read -p "Please input the filename what you want: " fileuser

# 2. 為了避免使用者隨意按 Enter ，利用變數功能分析檔名是否有設定？
filename=${fileuser:-"filename"}

# 3. 開始利用 date 指令來取得所需要的檔名了；
date1=`date --date='2 days ago' +%Y%m%d`
date2=`date --date='1 days ago' +%Y%m%d`
date3=`date +%Y%m%d`
file1="$filename""$date1"
file2="$filename""$date2"
file3="$filename""$date3"

# 4. 將檔名建立吧！
touch $file1
touch $file2
touch $file3

[root@linux scripts]# vi sh04.sh
#!/bin/bash
# Program:
# 	User can input 2 integer to cross by!
# History:
# 2005/08/23	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
echo -e "You SHOULD input 2 number, I will cross them! \n"
read -p "first number:  " firstnu
read -p "second number: " secnu
total=$(($firstnu*$secnu))
echo -e "\nThe number $firstnu x $secnu is ==> $total"

var=$((運算內容))

[root@linux scripts]# nu=$((13%3)); echo $nu
1

[root@linux ~]# test -e /dmtsai

[root@linux ~]# test -e /dmtsai && echo "exist" || echo "Not exist"

1. 這個檔案是否存在，若不存在則給予一個『Filename does not exist』的訊息，並中斷程式；
2. 若這個檔案存在，則判斷他是個檔案或目錄，結果輸出『Filename is regular file』或 『Filename is directory』
3. 判斷一下，執行者的身份對這個檔案或目錄所擁有的權限，並輸出權限資料！

[root@linux scripts]# vi sh05.sh
#!/bin/bash
# Program:
# 	Let user input a filename, the program will search the filename
#	1.) exist? 2.) file/directory? 3.) file permissions 
# History:
# 2005/08/25	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

# 1. 讓使用者輸入檔名，並且判斷使用者是否真的有輸入字串？
echo -e "The program will show you that filename is exist which input by you.\n\n"
read -p "Input a filename : " filename
test -z $filename && echo "You MUST input a filename." && exit 0
# 2. 判斷檔案是否存在？
test ! -e $filename && echo "The filename $filename DO NOT exist" && exit 0
# 3. 開始判斷檔案類型與屬性
test -f $filename && filetype="regulare file"
test -d $filename && filetype="directory"
test -r $filename && perm="readable"
test -w $filename && perm="$perm writable"
test -x $filename && perm="$perm executable"
# 4. 開始輸出資訊！
echo "The filename: $filename is a $filetype"
echo "And the permission are : $perm"

[root@linux ~]# [ -z "$HOME" ]

[  "$HOME"  ==  "$MAIL"  ]
[□"$HOME"□==□"$MAIL"□]
 ↑       ↑  ↑       ↑

• 在中括號 [] 內的每個元件都需要有空白鍵來分隔；
• 在中括號內的變數，最好都以雙引號來設定；
• 在中括號內的常數，最好都以單或雙引號來設定。

[root@linux ~]# name="VBird Tsai"
[root@linux ~]# [ $name == "VBird" ]
bash: [: too many arguments

[ VBird Tsai == "VBird" ]

[ "VBird Tsai" == "VBird" ]

1. 當執行一個程式的時候，這個程式會讓使用者選擇 Y 或 N ，
2. 如果使用者輸入 Y 或 y 時，就顯示『 OK, continue 』
3. 如果使用者輸入 n 或 N 時，就顯示『 Oh, interrupt ！』
4. 如果不是 Y/y/N/n 之內的其他字元，就顯示『I don't know what is your choice』

[root@linux scripts]# vi sh06.sh
#!/bin/bash
# Program:
# 	This program will show the user's choice
# History:
# 2005/08/25	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

read -p "Please input (Y/N): " yn
[ "$yn" == "Y" -o "$yn" == "y" ] && echo "OK, continue" && exit 0
[ "$yn" == "N" -o "$yn" == "n" ] && echo "Oh, interrupt!" && exit 0
echo "I don't know what is your choice" && exit 0

Tips

為什麼判斷式裡面下達等於要用 == 而不是一個 = 就好了呢？我們在前一章正規表示法裡面的 awk 提到， 只有一個 = 用來給予一個變數設定其內容，邏輯判斷時，則會給予兩個等於， 亦即『比較』而非『設定』的意思～這裡要好好的分辨一下喔！ ^_^

[root@linux ~]# /etc/init.d/crond restart

/path/to/scriptname  opt1  opt2  opt3  opt4  ...
       $0             $1    $2    $3    $4   ...

[root@linux scripts]# vi sh07.sh
#!/bin/bash
# Program:
# 	The program will show it's name and first 3 parameters.
# History:
# 2005/08/25	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

echo "The script name is ==> $0"
[ -n "$1" ] && echo "The 1st parameter is ==> $1" || exit 0
[ -n "$2" ] && echo "The 2nd parameter is ==> $2" || exit 0
[ -n "$3" ] && echo "The 3th parameter is ==> $3" || exit 0

[root@linux scripts]# sh sh07.sh theone haha quot
The script name is ==> sh07.sh
The 1st paramter is ==> theone
The 2nd paramter is ==> haha
The 3th paramter is ==> quot

if [ 條件判斷式 ]; then
	當條件判斷式成立時，可以進行的指令工作內容；
fi

• && 代表 AND ；
• || 代表 or ；

[root@linux scripts]# vi sh06-2.sh
#!/bin/bash
# Program:
# 	This program will show the user's choice
# History:
# 2005/08/25	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

read -p "Please input (Y/N): " yn

if [ "$yn" == "Y" ] || [ "$yn" == "y" ]; then
	echo "OK, continue"
	exit 0
fi
if [ "$yn" == "N" ] || [ "$yn" == "n" ]; then
	echo "Oh, interrupt!"
	exit 0
fi
echo "I don't know what is your choice" && exit 0

if [ 條件判斷式 ]; then
	當條件判斷式成立時，可以進行的指令工作內容；
else
	當條件判斷式不成立時，可以進行的指令工作內容；
fi

if [ 條件判斷式一 ]; then
	當條件判斷式一成立時，可以進行的指令工作內容；
elif [ 條件判斷式二 ]; then
	當條件判斷式二成立時，可以進行的指令工作內容；
else
	當條件判斷式一與二均不成立時，可以進行的指令工作內容；
fi

[root@linux scripts]# vi sh06-3.sh
#!/bin/bash
# Program:
# 	This program will show the user's choice
# History:
# 2005/08/25	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

read -p "Please input (Y/N): " yn

if [ "$yn" == "Y" ] || [ "$yn" == "y" ]; then
	echo "OK, continue"
elif [ "$yn" == "N" ] || [ "$yn" == "n" ]; then
	echo "Oh, interrupt!"
else
	echo "I don't know what is your choice"
fi

1. 如果是的話，就顯示 "Hello, how are you ?"；
2. 如果沒有加任何參數，就提示使用者必須要使用的參數下達法；
3. 而如果加入的參數不是 hello ，就提醒使用者僅能使用 hello 為參數。

[root@linux scripts]# vi sh08.sh
#!/bin/bash
# Program:
# 	Show "Hello" from $1....
# History:
# 2005/08/28	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

if [ "$1" == "hello" ]; then
	echo "Hello, how are you ?"
elif [ "$1" == "" ]; then
	echo "You MUST input parameters, ex> $0 someword"
else
	echo "The only parameter is 'hello'"
fi

[root@linux ~]# netstat -tuln
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address   Foreign Address    State
tcp        0      0 0.0.0.0:199     0.0.0.0:*          LISTEN
tcp        0      0 :::80           :::*               LISTEN
tcp        0      0 :::22           :::*               LISTEN
tcp        0      0 :::25           :::*               LISTEN

• 80: WWW
• 22: ssh
• 21: ftp
• 25: mail

[root@linux scripts]# vi sh09.sh
#!/bin/bash
# Program:
# 	Using netstat and grep to detect WWW,SSH,FTP and Mail services.
# History:
# 2005/08/28	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

# 1. 先作一些告知的動作而已～
echo "Now, the services of your Linux system will be detect!"
echo -e "The www, ftp, ssh, and mail will be detect! \n"

# 2. 開始進行一些測試的工作，並且也輸出一些資訊囉！
testing=`netstat -tuln | grep ":80 "`
if [ "$testing" != "" ]; then
	echo "WWW is running in your system."
fi
testing=`netstat -tuln | grep ":22 "`
if [ "$testing" != "" ]; then
	echo "SSH is running in your system."
fi
testing=`netstat -tuln | grep ":21 "`
if [ "$testing" != "" ]; then
	echo "FTP is running in your system."
fi
testing=`netstat -tuln | grep ":25 "`
if [ "$testing" != "" ]; then
	echo "Mail is running in your system."
fi

1. 先讓使用者輸入他們的退伍日期；
2. 再由現在日期比對退伍日期；
3. 由兩個日期的比較來顯示『還需要幾天』才能夠退伍的字樣。

[root@linux scripts]# vi sh10.sh
#!/bin/bash
# Program:
# 	Tring to calculate your demobilization date at how many days 
#	later...
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

# 1. 告知使用者這支程式的用途，並且告知應該如何輸入日期格式？
echo "This program will try to calculate :"
echo "How many days about your demobilization date..."
read -p "Please input your demobilization date (YYYYMMDD ex>20050401): " date2

# 2. 測試一下，這個輸入的內容是否正確？利用正規表示法囉～
date_d=`echo $date2 |grep '[0-9]\{8\}'`
if [ "$date_d" == "" ]; then
	echo "You input the wrong format of date...."
	exit 1
fi

# 3. 開始計算日期囉～
declare -i date_dem=`date --date="$date2" +%s`
declare -i date_now=`date +%s`
declare -i date_total_s=$(($date_dem-$date_now))
declare -i date_d=$(($date_total_s/60/60/24))
if [ "$date_total_s" -lt "0" ]; then
	echo "You had been demobilization before: " $((-1*$date_d)) " ago"
else
	declare -i date_h=$(($(($date_total_s-$date_d*60*60*24))/60/60))
	echo "You will be demobilized after $date_d days and $date_h hours."
fi

case $變數名稱 in
  "第一個變數內容")
	程式段
	;;
  "第二個變數內容")
	程式段
	;;
  *)
	不包含第一個變數內容與第二個變數內容的其他程式執行段
	exit 1
	;;
esac

[root@linux scripts]# vi sh08-2.sh
#!/bin/bash
# Program:
# 	Show "Hello" from $1.... by using case .... esac
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

case $1 in
  "hello")
	echo "Hello, how are you ?"
	;;
  "")
	echo "You MUST input parameters, ex> $0 someword"
	;;
  *)
	echo "Usage $0 {hello}"
	;;
esac

/etc/init.d/syslog restart

• 直接下達式：例如上面提到的，利用『 script.sh variable 』 的方式來直接給予 $1 這個變數的內容，這也是在 /etc/init.d 目錄下大多數程式的設計方式。
• 互動式：透過 read 這個指令來讓使用者輸入變數的內容。

[root@linux scripts]# vi sh11.sh
#!/bin/bash
# Program:
# 	Let user input one, two, three and show in screen.
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

echo "This program will print your selection !"
# read -p "Input your choice: " choice
# case $choice in
case $1 in
  "one")
	echo "Your choice is ONE"
	;;
  "two")
	echo "Your choice is TWO"
	;;
  "three")
	echo "Your choice is THREE"
	;;
  *)
	echo "Usage {one|two|three}"
	;;
esac

function fname() {
	程式段
}

[root@linux scripts]# vi sh11-2.sh
#!/bin/bash
# Program:
# 	Let user input one, two, three and show in screen.
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

function printit(){
	echo -n "Your choice is "
}

echo "This program will print your selection !"
case $1 in
  "one")
	printit; echo $1 | tr 'a-z' 'A-Z'
	;;
  "two")
	printit; echo $1 | tr 'a-z' 'A-Z'
	;;
  "three")
	printit; echo $1 | tr 'a-z' 'A-Z'
	;;
  *)
	echo "Usage {one|two|three}"
	;;
esac

[root@linux scripts]# vi sh11-3.sh
#!/bin/bash
# Program:
# 	Let user input one, two, three and show in screen.
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

function printit(){
	echo "Your choice is $1"
}

echo "This program will print your selection !"
case $1 in
  "one")
	printit 1
	;;
  "two")
	printit 2
	;;
  "three")
	printit 3
	;;
  *)
	echo "Usage {one|two|three}"
	;;
esac

while [ condition ]
do
	程式段落
done

until [ condition ]
do
	程式段落
done

[root@linux scripts]# vi sh12.sh
#!/bin/bash
# Program:
# 	Use loop to try find your input.
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

while [ "$yn" != "yes" ] && [ "$yn" != "YES" ]
do
	read -p "Please input yes/YES to stop this program: " yn
done

[root@linux scripts]# vi sh12-2.sh
#!/bin/bash
# Program:
# 	Use loop to try find your input.
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

until [ "$yn" == "yes" ] || [ "$yn" == "YES" ]
do
	read -p "Please input yes/YES to stop this program: " yn
done

[root@linux scripts]# vi sh13.sh
#!/bin/bash
# Program:
# 	Try to use loop to calculate the result "1+2+3...+100"
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

s=0
i=0
while [ "$i" != "100" ]
do
	i=$(($i+1))
	s=$(($s+$i))
done
echo "The result of '1+2+3+...+100' is ==> $s"

for (( 初始值; 限制值; 執行步階 ))
do
	程式段
done

• 初始值：某個變數在迴圈當中的起始值，直接以類似 i=1 設定好；
• 限制值：當變數的值在這個限制值的範圍內，就繼續進行迴圈。例如 i<=100；
• 執行步階：每作一次迴圈時，變數的變化量。例如 i=i+1。

[root@linux scripts]# vi sh14.sh
#!/bin/bash
# Program:
# 	Try do calculate 1+2+....+100
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

s=0
for (( i=1; i<=100; i=i+1 ))
do
	s=$(($s+$i))
done
echo "The result of '1+2+3+...+100' is ==> $s"

for var in con1 con2 con3 ...
do
	程式段
done

1. 第一次迴圈時， $var 的內容為 con1 ；
2. 第二次迴圈時， $var 的內容為 con2 ；
3. 第三次迴圈時， $var 的內容為 con3 ；
4. ....

[root@linux scripts]# vi sh15.sh
#!/bin/bash
# Program:
# 	Using for .... loop to print 3 animal 
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

for animal in dog cat elephant
do
	echo "There are ""$animal""s.... "
done

[root@linux scripts]# vi sh16.sh
#!/bin/bash
# Program:
# 	let user input a directory and find the whole file's permission.
# History:
# 2005/08/29	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

# 1. 先看看這個目錄是否存在啊？
read -p "Please input a directory: " dir
if [ "$dir" == "" ] || [ ! -d "$dir" ]; then
	echo "The $dir is NOT exist in your system."
	exit 1
fi

# 2. 開始測試檔案囉～
filelist=`ls $dir`
for filename in $filelist
do
	perm=""
	test -r "$dir/$filename" && perm="$perm readable"
	test -w "$dir/$filename" && perm="$perm writable"
	test -x "$dir/$filename" && perm="$perm executable"
	echo "The file $dir/$filename's permission is $perm "
done