perl學習筆記

1.perl版本
  perl -v 

2.注意：
註解 #
單行結束 ;
純量用 $ 開頭
純量陣列用@開頭
雜湊陣列用%開頭

用 my 或 local 宣告區域變數，反之為全域
字串雙引號夾注 "字串" ，數值不用引號
Perl只定義了一維陣列的語法，二維以上只能用指標間接來達成。

0 是false、非0 是ture

3.資料型態大致分為四種：Scalar純量、Scalar Array純量陣列、Hash Array雜湊、References指標
單數為scalar
複數為array
陣列個數 $#array
雜湊就是索引值不是數值的陣列

純量陣列宣告：
  (1)
my @array=qw(a b c d);
  (2)
my @array=("a","b","c","d");
  (3)
$array[0]="a"; $array[1]="b"; $array[2]="c"; $array[3]="d";



雜湊陣列宣告：
  (1)
my %hash=("i1"=>"aaa","i2"=>"bbb","i3"=>"ccc");
  (2)
my %hash=("i1","aaa","i2","bbb","i3","ccc");
  (3)
$hash{'i1'}="aaa"; $hash{'i2'}="bbb"; $hash{'i3'}="ccc";



下面是使用相關陣列的三個例子：
  (1)
foreach $key (keys %hash) {
print "$hash{$key}\n";
}

  (2)
foreach $value (values %hash)

  (3)
while(($key,$value)=each %hash)



4.字串運算子
字串比較的運算子有：

運算子	目的
x	返回 x 左側字串再重複 x 右側的次數。如： "測試"x3，返回 "測試測試測試"
．	連接 . 兩側的字串。如："測試"."字串"，返回 "測試字串"
eq	如果兩邊相等，返回 true ，反之，返回 false，即「==」
ne	如果兩邊不相等，返回 true ，反之，返回 false，即「!=」
le	如果左側小於或等於右側，返回 true ，反之，返回 false，即「<=」
lt	如果左側小於右側，返回 true ，反之，返回 false，即「<」
ge	如果左側大於或等於右側，返回 true ，反之，返回 false，即「>=」
gt	如果左側大於右側，返回 true ，反之，返回 false，即「>」
cmp	如果左側的字串小於、等於或大於右側，則返回-1,0或1。
,	Evaluates the left operand, the evaluates the right operand. It returns the result of the right operand.
++	將字串增加一個字母值

5.數值運算子

數值運算子	目的
+	Computes the additive value of the two operands.
-	Computes the difference between the two operands.
*	Computes the multiplication of the two operands.
/	Computes the division between the two operands.
%	Computes the modulus(remainder) of the two operands.
= =	Returns Ture if the two operands are equivalent, False otherwise.
!=	Returns Ture if the two operands are not equal, False otherwise.
<=	Returns Ture if the operand on the left is numerically less than or equal to the operand on the right of the operator. Returns False otherwise.
=>	Returns Ture if the operand on the left is numerically greater than or equal to the operand on the right of the operator. Returns False otherwise.
<	Returns Ture if the operand on the left is numerically less than the operand on the right of the operator. Returns False otherwise.
>	Returns Ture if the operand on the left is numerically greater than the operand on the right of the operator. Returns False otherwise.
< = >	Returns -1 if the left operand is less than the right, +1 if is it greater than, and 0(False) otherwise.
&&	Performs a logical AND operation. If the left operand is True m then the right operator is not evaluated.
||	Performs a logical OR operation. If the left operand is True m then the right operator is not evaluated.
&	Returns the valueof the two operators bitwise ANDed.
|	Returns the valueof the two operators bitwise ORed.
^	Returns the valueof the two operators bitwise XORed.
++	Increment operator. Increments the variable's value by 1.
--	Decrement operator. Decrements the variable's value by 1.
**	Computes the power of the left-hand value to the power of the rihght-hand value.
+=	Adds the value of the right-hand operand to the value of the left-hand operand.
-+	Subtracts the value of the right-hand operand to the value of the left-hand operand.
*=	Mlutiplies the value of the left-hand operand to the value of the right-hand operand.
>>	Shifts the left operand right by the number of bits that is specified by the right operand.
<<	Shifts the left operand left by the number of bits that is specified by the right operand.
~	Performs a 1s complement of the operator. This is a unary operator.

6.控制流程

(1)if
if (條件) {程式碼}
if (條件) {程式碼} else {程式碼}
if (條件) {程式碼} elsif (程式碼) {程式碼} else {程式碼}

(2)for
for($i=0; $i<=10; $i++) {程式碼}
for $i (0..10) {程式碼}

(3)foreach
for($i=0; $i<=$#array; $i++)

foreach $i (@array) {程式碼}


(4)while和do
while($i<=10) {程式碼}

do {Code Segment} while(程式碼);

(5)last是跳出現在所在的迴圈，next則是跳過下面的指令直接執行下一次的迴圈。

while(chomp($i=<STDIN>)) {
next if ($i == 5);
last unless ($i > 10);
}


參考資料：
http://ind.ntou.edu.tw/~dada/cgi/Perlsynx.htm