第十二章、學習 Shell Scripts

[dmtsai@study ~]$ mkdir bin; cd bin
[dmtsai@study bin]$ vim hello.sh
#!/bin/bash
# Program:
#       This program shows "Hello World!" in your screen.
# History:
# 2015/07/16	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

[dmtsai@study bin]$ sh hello.sh
Hello World !

[dmtsai@study bin]$ vim showname.sh
#!/bin/bash
# Program:
#	User inputs his first name and last name.  Program shows his full name.
# History:
# 2015/07/16	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      # 提示使用者輸入
read -p "Please input your last name:  " lastname       # 提示使用者輸入
echo -e "\nYour full name is: ${firstname} ${lastname}" # 結果由螢幕輸出

[dmtsai@study bin]$ vim create_3_filename.sh
#!/bin/bash
# Program:
#	Program creates three files, which named by user's input and date command.
# History:
# 2015/07/16	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." # 純粹顯示資訊
read -p "Please input your filename: " fileuser         # 提示使用者輸入

# 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"}           # 開始判斷有否設定檔名

# 3. 開始利用 date 指令來取得所需要的檔名了；
date1=$(date --date='2 days ago' +%Y%m%d)  # 前兩天的日期
date2=$(date --date='1 days ago' +%Y%m%d)  # 前一天的日期
date3=$(date +%Y%m%d)                      # 今天的日期
file1=${filename}${date1}                  # 底下三行在設定檔名
file2=${filename}${date2}
file3=${filename}${date3}

# 4. 將檔名建立吧！
touch "${file1}"                           # 底下三行在建立檔案
touch "${file2}"
touch "${file3}"

[dmtsai@study bin]$ vim multiplying.sh
#!/bin/bash
# Program:
#	User inputs 2 integer numbers; program will cross these two numbers.
# History:
# 2015/07/16	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 numbers, I will multiplying them! \n"
read -p "first number:  " firstnu
read -p "second number: " secnu
total=$((${firstnu}*${secnu}))
echo -e "\nThe result of ${firstnu} x ${secnu} is ==> ${total}"

[dmtsai@study bin]$ echo $(( 13 % 3 ))
1

[dmtsai@study bin]$ echo "123.123*55.9" | bc
6882.575

[dmtsai@study bin]$ vim cal_pi.sh
#!/bin/bash
# Program:
#	User input a scale number to calculate pi number.
# History:
# 2015/07/16	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
echo -e "This program will calculate pi value. \n"
echo -e "You should input a float number to calculate pi value.\n"
read -p "The scale number (10~10000) ? " checking
num=${checking:-"10"}           # 開始判斷有否有輸入數值
echo -e "Starting calculate pi value.  Be patient."
time echo "scale=${num}; 4*a(1)" | bc -lq

[dmtsai@study bin]$ echo ${firstname} ${lastname}
    <==確認了，這兩個變數並不存在喔！
[dmtsai@study bin]$ sh showname.sh
Please input your first name: VBird <==這個名字是鳥哥自己輸入的
Please input your last name:  Tsai 

Your full name is: VBird Tsai      <==看吧！在 script 運作中，這兩個變數有生效
[dmtsai@study bin]$ echo ${firstname} ${lastname}
    <==事實上，這兩個變數在父程序的 bash 中還是不存在的！

[dmtsai@study bin]$ source showname.sh
Please input your first name: VBird
Please input your last name:  Tsai

Your full name is: VBird Tsai
[dmtsai@study bin]$ echo ${firstname} ${lastname}
VBird Tsai  <==嘿嘿！有資料產生喔！

[dmtsai@study ~]$ test -e /dmtsai

[dmtsai@study ~]$ test -e /dmtsai && echo "exist" || echo "Not exist"
Not exist  <==結果顯示不存在啊！

[dmtsai@study bin]$ vim file_perm.sh
#!/bin/bash
# Program:
#	User input a filename, program will check the flowing:
#	1.) exist? 2.) file/directory? 3.) file permissions 
# History:
# 2015/07/16	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 "Please input a filename, I will check the filename's type and permission. \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？若不存在則顯示訊息並結束腳本
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 permissions for you are : ${perm}"

[dmtsai@study ~]$ [ -z "${HOME}" ] ; echo $?

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

[dmtsai@study ~]$ name="VBird Tsai"
[dmtsai@study ~]$ [ ${name} == "VBird" ]
bash: [: too many arguments

[dmtsai@study bin]$ vim ans_yn.sh
#!/bin/bash
# Program:
# 	This program shows the user's choice
# History:
# 2015/07/16	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 your choice is" && exit 0

[dmtsai@study ~]$ file /etc/init.d/network
/etc/init.d/network: Bourne-Again shell script, ASCII text executable
# 使用 file 來查詢後，系統告知這個檔案是個 bash 的可執行 script 喔！
[dmtsai@study ~]$ /etc/init.d/network restart

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

[dmtsai@study bin]$ vim how_paras.sh
#!/bin/bash
# Program:
#	Program shows the script name, parameters...
# History:
# 2015/07/16	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}"
echo "Total parameter number is ==> $#"
[ "$#" -lt 2 ] && echo "The number of parameter is less than 2.  Stop here." && exit 0
echo "Your whole parameter is   ==> '$@'"
echo "The 1st parameter         ==> ${1}"
echo "The 2nd parameter         ==> ${2}"

[dmtsai@study bin]$ sh how_paras.sh theone haha quot
The script name is        ==> how_paras.sh       <==檔名
Total parameter number is ==> 3                  <==果然有三個參數
Your whole parameter is   ==> 'theone haha quot' <==參數的內容全部
The 1st parameter         ==> theone             <==第一個參數
The 2nd parameter         ==> haha               <==第二個參數

[dmtsai@study bin]$ vim shift_paras.sh
#!/bin/bash
# Program:
#	Program shows the effect of shift function.
# History:
# 2009/02/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

echo "Total parameter number is ==> $#"
echo "Your whole parameter is   ==> '$@'"
shift   # 進行第一次『一個變數的 shift 』
echo "Total parameter number is ==> $#"
echo "Your whole parameter is   ==> '$@'"
shift 3 # 進行第二次『三個變數的 shift 』
echo "Total parameter number is ==> $#"
echo "Your whole parameter is   ==> '$@'"

[dmtsai@study bin]$ sh shift_paras.sh one two three four five six <==給予六個參數
Total parameter number is ==> 6   <==最原始的參數變數情況
Your whole parameter is   ==> 'one two three four five six'
Total parameter number is ==> 5   <==第一次偏移，看底下發現第一個 one 不見了
Your whole parameter is   ==> 'two three four five six'
Total parameter number is ==> 2   <==第二次偏移掉三個，two three four 不見了
Your whole parameter is   ==> 'five six'

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   <==將 if 反過來寫，就成為 fi 啦！結束 if 之意！

[dmtsai@study bin]$ cp ans_yn.sh ans_yn-2.sh  <==用複製來修改的比較快！
[dmtsai@study bin]$ vim ans_yn-2.sh
#!/bin/bash
# Program:
#       This program shows the user's choice
# History:
# 2015/07/16    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 your choice is" && exit 0

# 一個條件判斷，分成功進行與失敗進行 (else)
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

# 多個條件判斷 (if ... elif ... elif ... else) 分多種不同情況執行
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

[dmtsai@study bin]$ cp ans_yn-2.sh ans_yn-3.sh
[dmtsai@study bin]$ vim ans_yn-3.sh
#!/bin/bash
# Program:
#       This program shows the user's choice
# History:
# 2015/07/16    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 your choice is"
fi

[dmtsai@study bin]$ vim hello-2.sh
#!/bin/bash
# Program:
#	Check $1 is equal to "hello"
# History:
# 2015/07/16	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> {${0} someword}"
else
	echo "The only parameter is 'hello', ex> {${0} hello}"
fi

[dmtsai@study ~]$ netstat -tuln
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN
tcp6       0      0 :::22                   :::*                    LISTEN
tcp6       0      0 ::1:25                  :::*                    LISTEN
udp        0      0 0.0.0.0:123             0.0.0.0:*
udp        0      0 0.0.0.0:5353            0.0.0.0:*
udp        0      0 0.0.0.0:44326           0.0.0.0:*
udp        0      0 127.0.0.1:323           0.0.0.0:*
udp6       0      0 :::123                  :::*
udp6       0      0 ::1:323                 :::*
#封包格式           本地IP:埠口             遠端IP:埠口             是否監聽

[dmtsai@study bin]$ vim netstat.sh
#!/bin/bash
# Program:
# 	Using netstat and grep to detect WWW,SSH,FTP and Mail services.
# History:
# 2015/07/16	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, I will detect your Linux server's services!"
echo -e "The www, ftp, ssh, and mail(smtp) will be detected! \n"

# 2. 開始進行一些測試的工作，並且也輸出一些資訊囉！
testfile=/dev/shm/netstat_checking.txt
netstat -tuln > ${testfile}          # 先轉存資料到記憶體當中！不用一直執行 netstat
testing=$(grep ":80 " ${testfile})   # 偵測看 port 80 在否？
if [ "${testing}" != "" ]; then
	echo "WWW is running in your system."
fi
testing=$(grep ":22 " ${testfile})   # 偵測看 port 22 在否？
if [ "${testing}" != "" ]; then
	echo "SSH is running in your system."
fi
testing=$(grep ":21 " ${testfile})   # 偵測看 port 21 在否？
if [ "${testing}" != "" ]; then
	echo "FTP is running in your system."
fi
testing=$(grep ":25 " ${testfile})   # 偵測看 port 25 在否？
if [ "${testing}" != "" ]; then
	echo "Mail is running in your system."
fi

[dmtsai@study bin]$ vim cal_retired.sh
#!/bin/bash
# Program:
#	You input your demobilization date, I calculate how many days before you demobilize.
# History:
# 2015/07/16	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 before your demobilization date..."
read -p "Please input your demobilization date (YYYYMMDD ex>20150716): " 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 ${date2} |grep '[0-9]\{8\}')   # 看看是否有八個數字
if [ "${date_d}" == "" ]; then
	echo "You input the wrong date format...."
	exit 1
fi

# 3. 開始計算日期囉～
declare -i date_dem=$(date --date="${date2}" +%s)      # 退伍日期秒數
declare -i date_now=$(date +%s)                        # 現在日期秒數
declare -i date_total_s=$((${date_dem}-${date_now}))   # 剩餘秒數統計
declare -i date_d=$((${date_total_s}/60/60/24))        # 轉為日數
if [ "${date_total_s}" -lt "0" ]; then                 # 判斷是否已退伍
	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 demobilize after ${date_d} days and ${date_h} hours."
fi

case  $變數名稱 in   <==關鍵字為 case ，還有變數前有錢字號
  "第一個變數內容")   <==每個變數內容建議用雙引號括起來，關鍵字則為小括號 )
	程式段
	;;            <==每個類別結尾使用兩個連續的分號來處理！
  "第二個變數內容")
	程式段
	;;
  *)                  <==最後一個變數內容都會用 * 來代表所有其他值
	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                  <==最終的 case 結尾！『反過來寫』思考一下！

[dmtsai@study bin]$ vim hello-3.sh
#!/bin/bash
# Program:
# 	Show "Hello" from $1.... by using case .... esac
# History:
# 2015/07/16	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}"
	;;
  *)   # 其實就相當於萬用字元，0~無窮多個任意字元之意！
	echo "Usage ${0} {hello}"
	;;
esac

[dmtsai@study bin]$ vim show123.sh
#!/bin/bash
# Program:
#	This script only accepts the flowing parameter: one, two or three.
# History:
# 2015/07/17	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   # 暫時取消，可以替換！
# case ${choice} in                      # 暫時取消，可以替換！
case ${1} in                             # 現在使用，可以用上面兩行替換！
  "one")
	echo "Your choice is ONE"
	;;
  "two")
	echo "Your choice is TWO"
	;;
  "three")
	echo "Your choice is THREE"
	;;
  *)
	echo "Usage ${0} {one|two|three}"
	;;
esac

function fname() {
	程式段
}

[dmtsai@study bin]$ vim show123-2.sh
#!/bin/bash
# Program:
#	Use function to repeat information.
# History:
# 2015/07/17	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 "     # 加上 -n 可以不斷行繼續在同一行顯示
}

echo "This program will print your selection !"
case ${1} in
  "one")
	printit; echo ${1} | tr 'a-z' 'A-Z'  # 將參數做大小寫轉換！
	;;
  "two")
	printit; echo ${1} | tr 'a-z' 'A-Z'
	;;
  "three")
	printit; echo ${1} | tr 'a-z' 'A-Z'
	;;
  *)
	echo "Usage ${0} {one|two|three}"
	;;
esac

[dmtsai@study bin]$ vim show123-3.sh
#!/bin/bash
# Program:
#	Use function to repeat information.
# History:
# 2015/07/17	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}"   # 這個 $1 必須要參考底下指令的下達
}

echo "This program will print your selection !"
case ${1} in
  "one")
	printit 1  # 請注意， printit 指令後面還有接參數！
	;;
  "two")
	printit 2
	;;
  "three")
	printit 3
	;;
  *)
	echo "Usage ${0} {one|two|three}"
	;;
esac

while [ condition ]  <==中括號內的狀態就是判斷式
do            <==do 是迴圈的開始！
	程式段落
done          <==done 是迴圈的結束

until [ condition ]
do
	程式段落
done

[dmtsai@study bin]$ vim yes_to_stop.sh
#!/bin/bash
# Program:
#	Repeat question until user input correct answer.
# History:
# 2015/07/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

while [ "${yn}" != "yes" -a "${yn}" != "YES" ]
do
	read -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."

[dmtsai@study bin]$ vim yes_to_stop-2.sh
#!/bin/bash
# Program:
#	Repeat question until user input correct answer.
# History:
# 2015/07/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

until [ "${yn}" == "yes" -o "${yn}" == "YES" ]
do
	read -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."

[dmtsai@study bin]$ vim cal_1_100.sh
#!/bin/bash
# Program:
#	Use loop to calculate "1+2+3+...+100" result.
# History:
# 2015/07/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

s=0  # 這是加總的數值變數
i=0  # 這是累計的數值，亦即是 1, 2, 3....
while [ "${i}" != "100" ]
do
	i=$(($i+1))   # 每次 i 都會增加 1 
	s=$(($s+$i))  # 每次都會加總一次！
done
echo "The result of '1+2+3+...+100' is ==> $s"

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

[dmtsai@study bin]$ vim show_animal.sh
#!/bin/bash
# Program:
# 	Using for .... loop to print 3 animals
# History:
# 2015/07/17	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

[dmtsai@study bin]$ vim userid.sh
#!/bin/bash
# Program
#       Use id, finger command to check system account's information.
# History
# 2015/07/17    VBird   first release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
users=$(cut -d ':' -f1 /etc/passwd)    # 擷取帳號名稱
for username in ${users}               # 開始迴圈進行！
do
        id ${username}
done

[dmtsai@study bin]$ vim pingip.sh
#!/bin/bash
# Program
#       Use ping command to check the network's PC state.
# History
# 2015/07/17    VBird   first release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
network="192.168.1"              # 先定義一個網域的前面部分！
for sitenu in $(seq 1 100)       # seq 為 sequence(連續) 的縮寫之意
do
	# 底下的程式在取得 ping 的回傳值是正確的還是失敗的！
        ping -c 1 -w 1 ${network}.${sitenu} &> /dev/null && result=0 || result=1
	# 開始顯示結果是正確的啟動 (UP) 還是錯誤的沒有連通 (DOWN)
        if [ "${result}" == 0 ]; then
                echo "Server ${network}.${sitenu} is UP."
        else
                echo "Server ${network}.${sitenu} is DOWN."
        fi
done

[dmtsai@study bin]$ vim dir_perm.sh
#!/bin/bash
# Program:
#	User input dir name, I find the permission of files.
# History:
# 2015/07/17	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 [ "${dir}" == "" -o ! -d "${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})        # 列出所有在該目錄下的檔案名稱
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

for (( 初始值; 限制值; 執行步階 ))
do
	程式段
done

[dmtsai@study bin]$ vim cal_1_100-2.sh
#!/bin/bash
# Program:
# 	Try do calculate 1+2+....+${your_input}
# History:
# 2015/07/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

read -p "Please input a number, I will count for 1+2+...+your_input: " nu

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

[dmtsai@study bin]$ vim what_to_eat.sh
#!/bin/bash
# Program:
# 	Try do tell you what you may eat.
# History:
# 2015/07/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

eat[1]="賣噹噹漢堡"       # 寫下你所收集到的店家！
eat[2]="肯爺爺炸雞"
eat[3]="彩虹日式便當"
eat[4]="越油越好吃大雅"
eat[5]="想不出吃啥學餐"
eat[6]="太師父便當"
eat[7]="池上便當"
eat[8]="懷念火車便當"
eat[9]="一起吃泡麵"
eatnum=9                  # 需要輸入有幾個可用的餐廳數！

check=$(( ${RANDOM} * ${eatnum} / 32767 + 1 ))
echo "your may eat ${eat[${check}]}"

[dmtsai@study bin]$ vim what_to_eat-2.sh
#!/bin/bash
# Program:
# 	Try do tell you what you may eat.
# History:
# 2015/07/17	VBird	First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

eat[1]="賣噹噹漢堡"
eat[2]="肯爺爺炸雞"
eat[3]="彩虹日式便當"
eat[4]="越油越好吃大雅"
eat[5]="想不出吃啥學餐"
eat[6]="太師父便當"
eat[7]="池上便當"
eat[8]="懷念火車便當"
eat[9]="一起吃泡麵"
eatnum=9

eated=0
while [ "${eated}" -lt 3 ]; do
        check=$(( ${RANDOM} * ${eatnum} / 32767 + 1 ))
        mycheck=0
        if [ "${eated}" -ge 1 ]; then
                for i in $(seq 1 ${eated} )
                do
                        if [ ${eatedcon[$i]} == $check ]; then
                                mycheck=1
                        fi
                done
        fi
        if [ ${mycheck} == 0 ]; then
                echo "your may eat ${eat[${check}]}"
                eated=$(( ${eated} + 1 ))
                eatedcon[${eated}]=${check}
        fi
done