Shbang行

"shbang" 是腳本起始行，告訴kernel那個shell解析. #!位于行頭。例如 #!/bin/ksh

注釋

行注釋用#符號.例如：

# This program will test some files

通配符

*,?, 和 [ ]用于文件名擴展.例如<, >, 2>, >>, 和 | 用于IO和重定向. 為了保證這些符號不被解析，這個字符要被引起來。 例如：rm *; ls ??;  cat file[1-3];

echo "How are you?"

輸出顯示

輸出屏幕echo和print,例如：

echo "Who are you?"

print "How are you?"

局部變量

局部變量作用于當前shell，shell結束時局部變量失效.例如

variable_name=value

typeset variable_name=value

name="John Doe"

x=5

全局變量

全局變量也稱為環境變量. 例如：

export VARIABLE_NAME =value

export PATH=/bin:/usr/bin:.

從變量中提取值

使用$.例如：

echo $variable_name

echo $name

echo $PATH

讀取用戶輸入

使用read。例如：

read name?"What is your name?"

The prompt is in quotes. After it is displayed, the read command waits for user input

print -n "What is your name?"

read name

read name1 name2 ...

參數

可以從命令行傳入參數。位置參數用于從腳本中接收值。例如：

At the command line:

$ scriptname arg1 arg2 arg3 ...

In a script:

echo $1 $2 $

位置參數, $1 分配為 arg1, $2 is 分配為arg2, ...

echo $*

所有位置參數

echo $#

位置參數號

數組

Bourne shell 利用位置參數創建字符列表.除位置參數外,Korn shell也支持數組語法，起始位置為0. Korn shell數組用set –A命令創建.例如

set apples pears peaches

位置參數

print $1 $2 $3

$1 is apples, $2 is pears, $3 is peaches

set -A array_name word1 word2 word3 ...

set -A fruit apples pears plums

Array

print ${fruit[0]}

Prints apple

${fruit[1]} = oranges

Assign a new value

算術

Korn shell 支持整數算術.typeset i命令會聲明一個整數類型變量. Integer算術能夠在變量上完成。否則，(( )) 語法 (let command)用于算術操作。例如：

typeset -i variable_name

聲明integer

typeset -i num

num=5+4

num is declared as an integer

print $num

Prints 9

(( n=5 + 5 ))

The let command

print $n

Prints 10

命令替換

像C/TC shells 和Bourne shell，Korn shell提供一種新的語法，將命名放在（）中，前面加$.例如：

variable_name=`command`

variable_name=$( command )

echo $variable_name

echo "Today is `date`"

echo "Today is $(date)"

操作符

Korn shell使用內建的test命令操作符，類似于C 語言操作符.例如：

相等性:

比較性:

=

string, equal to

> 

greater than

!=

string, not equal to

>=

greater than, equal to

==

number, equal to

< 

less than

!=

number, not equal to

<=

less than, equal to

邏輯性:

&&

and

||

Or

!

Not

條件語句

if 語句條件放在（）。then關鍵字位于（）后. If用fi結束. [[ ]] 用于模式匹配. [ ]用于兼容Bourne shell. Case命令是另外一種if/else.例如：

The if construct is:

if command

then

   block of statements

fi

----------------------------

if [[ string expression ]]

then

   block of statements

fi

----------------------------

if (( numeric expression ))

then

   block of statements

fi

The if/else construct is:

if command

then

   block of statements

else

   block of statements

fi

--------------------------

if [[ expression ]]

then

   block of statements

else

   block of statements

fi

---------------------------

if (( numeric expression ))

then

   block of statements

else

   block of statements

fi

The case construct is:

case variable_name in

   pattern1)

      statements

         ;;

   pattern2)

      statements

         ;;

   pattern3)

         ;;

esac

-------------------------

case "$color" in

   blue)

      echo $color is blue

         ;;

   green)

      echo $color is green

         ;;

   red|orange)

      echo $color is red or orange

         ;;

esac

The if/else/else if construct is:

if command

then

   block of statements

elif command

then

   block of statements

elif command

then

   block of statements

else

   block of statements

fi

---------------------------

if [[ string expression ]]

then

   block of statements

elif [[ string expression ]]

then

   block of statements

elif [[ string expression ]]

then

   block of statements

else

   block of statements

fi

----------------------------

if (( numeric expression ))

then

   block of statements

elif (( numeric expression ))

then

   block of statements

elif (( numeric expression ))

then

   block of statements

else

   block of statements

fi

循環

四種類型循環： while, until, for, 和 select.

while循環 跟隨do。

until循環。

for循環。

select loop is used to provide a prompt (PS3 variable) and a menu of numbered items from which the user inputs a selection The input will be stored in the special built-in REPLY variable. The select loop is normally used with the case command.

循環控制命令，例如：

while command

do

   block of statements

done

----------------------------

while [[ string expression ]]

do

   block of statements

done

---------------------------

while (( numeric expression ))

do

    block of statements

done

until command

do

block of statements

done

----------------------------

until [[ string expression ]]

do

   block of statements

done

----------------------------

until (( numeric expression ))

do

   block of statements

done

for variable in word_list

do

   block of statements

done

-----------------------------

for name in Tom Dick Harry

do

   print "Hi $name"

done

select variable in word_list

do

   block of statements

done    

----------------------------

PS3="Select an item from the menu"

for item in blue red green

   echo $item

done

Shows menu:

1. blue
2. red
3. green

文件測試

Korn shell使用test command來評估表達式，例如：

-d

File is a directory

-a

File exists and is not a directory

–r

Current user can read the file

–s

File is of nonzero size

–w

Current user can write to the file

–x

Current user can execute the file

Example 2.5.

   #!/bin/sh

1   if [ –a file ]

    then

      echo file exists

   fi

2    if [ –d file ]

    then

        echo file is a directory

   fi

3   if [ -s file ]

    then

       echo file is not of zero length

   fi

4   if [ -r file -a -w file ]

    then

       echo file is readable and writable

   fi

函數

函數容許定義一段shell，而且給這段代碼給一個名字.有兩種格式:一種來自于Bourne shell,另一種來自于Korn shell.例如：

function_name() {

   block of code

}

function function_name {

   block of code

}

-------------------------

function lister {

   echo Your present working directory is `pwd`

   echo Your files are:

   ls

}