perl 快速学习记录

$x = 12345;
$var1 = 047; #等于十进制的39
$var2 = 0x1f; #等于十进制的31

$value = 9.01e+21 + 0.01 - 9.01e+21;
print ("first value is ", $value, "\n");

$value = 9.01e+21 - 9.01e+21 + 0.01;
print ("second value is ", $value, "\n");

$number = 11;
$text = "This text contains the number $number.";
# This text contains the number 11.

$string = "43";
$number = 28;
$result = $string + $number;  # $result = 71

$result = "hello" * 5;  # $result = 0
$result = "12a34" +1;  # $result = 13

$stringvar = "abc";
$stringvar++; # $stringvar contains "abd" now

$stringvar = "aBC";
$stringvar++; # $stringvar contains "aBD" now

$stringvar = "abz";
$stringvar++; # $stringvar now contains "aca"

$stringvar = "AGZZZ";
$stringvar++; # $stringvar now contains "AHAAA" 

$stringvar = "ab4";
$stringvar++; # $stringvar now contains "ab5"

$stringvar = "bc999";
$stringvar++; # $stringvar now contains "bd000" 

$stringvar = "ab*c";
$stringvar++; # 1

$stringvar = "ab5c";
$stringvar++; # 1

$newstring = "potato" . "head"; # "potatohead"

$newstring = "t" x 2; # "potatoheadpotatohead"

$a = "be";
$a .= "witched"; # "bewitched"

$condvar == 43 ? $var1 : $var2 = 14; 
$condvar == 43 ? $var1 = 14 : $var2 = 14;

@array = (1, 2, 3);

@array = (1, 2, 3, 4);
$scalar = $array[0];

$array[3] = 5; # now @array is (1,2,3,5)

$scalar = $array[4]; # now $scalar = null;

$array[6] = 17; # now @array is (1,2,3,5,"","",17)

@result = @original; 

@list1 = (2, 3, 4);
@list2 = (1, @list1, 5); # @list2 = (1, 2, 3, 4, 5)

@array = (5, 7, 11);
($var1, $var2) = @array; # $var1 = 5, $var2 = 7, 11被忽略

@array = (5, 7);
($var1, $var2, $var3) = @array; # $var1 = 5, $var2 = 7, $var3 ="" (null)

"$var[0]"  #为数组@var的第一个元素。
"$var\[0]" #将字符"["转义，等价于"$var". "[0]"，$var被变量替换，[0]保持不变。
"${var}[0]"  #亦等价于"$var" ."[0]"。
"$\{var}" #则取消了大括号的变量替换功能，包含文字：${var}.

#用于整数
(1..10) = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
(2, 5..7, 11) = (2, 5, 6, 7, 11)
(3..3) = (3)

#用于实数
(2.1..5.3) = (2.1, 3.1 ,4.1, 5.1)
(4.5..1.6) = ()

#用于字符串
("aaa".."aad") = ("aaa","aab", "aac", "aad")
@day_of_month = ("01".."31")

#可包含变量或表达式
($var1..$var2+5)

#小技巧
$fred = "Fred";
print (("Hello, " . $fred . "!\n") x 2);  # "Hello, Fred!\nHello, Fred! \n"

@array = (1, 2, 3);
print (@array, "\n"); #123

@array = (1, 2, 3);
print ("@array\n"); #1 2 3

@array = (1, 2, 3);
$scalar = @array; # $scalar = 3,即@array的长度
($scalar) = @array; # $scalar = 1,即@array第一个元素的值

#以数组的长度为循环次数可如下编程
$count = 1;
while ($count <= @array) {
    print ("element $count: $array[$count-1]\n");
    $count++;
}

@array = (1, 2, 3, 4, 5);
@subarray = @array[0,1]; # @subarray = (1, 2)
@subarray2 = @array[1..3]; # @subarray2 = (2,3,4)

@array[0,1] = ("string", 46); # @array =("string",46,3,4,5) now 
@array[0..3] = (11, 22, 33, 44); # @array = (11,22,33,44,5) now
@array[1,2,3] = @array[3,2,4]; # @array = (11,44,33,5,5) now
@array[0..2] = @array[3,4]; # @array = (5,5,"",5,5) now


@array[1,2] = @array[2,1]; #用子数组形式来交换元素

@array = ("this", "is", "a","test");
@array2 = sort(@array); # @array2 = ("a","is", "test", "this")
@array = (70, 100, 8);
@array = sort(@array); # @array = (100, 70, 8) now

@array2 = reverse(@array);
@array2 = reverse sort (@array);

@list = ("rabbit", "12345","quartz");
chop (@list); # @list = ("rabbi", "1234","quart") now

$string = join(" ", "this", "is","a", "string"); # 结果为"this is a string"
@list = ("words","and");
$string = join("::", @list, "colons"); #结果为"words::and::colons"
@array = split(/::/,$string); # @array = ("words","and", "colons") now

# 返回值用来确定打开文件的操作是否成功，当其成功时返回非零值，失败时返回零
open(FILE1,"file1"); #读

# 写模式将原文件覆盖，原有内容丢失
open(outfile,">outfile"); # 写模式 

# 添加模式则在原文件的末尾处继续添加内容
open(appendfile, ">>appendfile")； # 添加模式 

#  关闭文件
close(MYFILE);

# 从文件中读取一行数据,文件指针向后移动一行
$line = <MYFILE>;  

# 把文件的全部内容读入数组
# 文件的每一行(含回车符)为数组的一个元素
@array = <MYFILE>;

open(OUTFILE, ">outfile");
print OUTFILE ("Here is an output line.\n");

if (-e "/path/file1") {
    print STDERR ("File file1 exists.\n");
}

$var = $ARGV[0]; # 第一个参数
$numargs = @ARGV; # 参数的个数

@ARGV = ("myfile1", "myfile2"); #实际上由命令行参数赋值
while ($line = <>) {
    print ($line);
} 

# 打开一个管道，发送到MESSAGE的输出成为命令"mail dave"的输入
open (MESSAGE, "| mail dave"); 
print MESSAGE ("Hi, Dave! Your Perl program sent this!\n");
close (MESSAGE);

@array = split(/ /, $line);

$var = "abcd";

$result = $var =~ /bc/; # 非零值
$result = $var =~ /cb/; # 0

$pattern = "\d{2}([\W])\d{2}\1\d{2}"

"12-05-92" =~ /$pattern/;  #true
"26.11.87" =~ /$pattern/;  #true
"07 04 92" =~ /$pattern/;  #true
"07 04-92" =~ /$pattern/;  #false

m!/u/jqpublic/perl/prog1! #等价于/\/u\/jqpublic\/perl\/prog1/

$string = "This string contains the number 25.11.";
 $string =~ /-?(\d+)\.?(\d+)/; # 匹配结果为25.11
 $integerpart = $1; # now $integerpart = 25
 $decimalpart = $2; # now $decimalpart = 11
 $totalpart = $&; # now totalpart = 25.11

$string = "abc123def";
$string =~ s/123/456/; # now $string = "abc456def";

if ( <expression>) {
    # statement_block_1
}elsif ( <expression> ) {
    # statement_block_2
}else{
    # statement_block_3
}

#while循环 
while ( <expression> ) {
    # statement_block
}

#until循环 
until ( <expression> ) {
    # statement_block
}

#类C的for循环
for ($count=1; $count <= 5; $count++) {
    # statements inside the loop go here
}


#列表(数组)循环

foreach localvar (listexpr) {
    #statement_block;
}

# 等价于
foreach $word (@words) {
    if ($word eq "the") {
      print ("found the word 'the'\n"); 
    }
}


# do循环
#至少执行一次循环
do {
    statement_block
} while_or_until (condexpr);

@list = (1, 2, 3, 4, 5);
foreach $temp (@list) {
    if ($temp == 2) {
        $temp = 20;
    }
}

#@list已变成了(1, 20, 3, 4, 5)。

print ("This is zero.\n") if ($var == 0);
print ("This is zero.\n") unless ($var != 0);
print ("Not zero yet.\n") while ($var-- > 0);
print ("Not zero yet.\n") until ($var-- == 0);

sub subroutine{
    statements;
}

# 使用在定义之前
sub subname1{

}

subname1;

# 使用在定义之后
&subname2;

#也可以使用 do 调用

do subname2()

sub subname2{

}

# 使用在定义之后， 不过之前有声明
sub subname3;

subname3;

sub subname3{

}

my($scalar) = 43;
local(@array) = (1, 2, 3);

&sub1(&number1, $number2, $nubmer3);

sub sub1{
    my($number1, $number2, $number3) = @_;
}


&addlist (@mylist);
&addlist ("14", "6", "11");
&addlist ($value1, @sublist, $value2);

sub addlist {
    my (@list) = @_;
}

&twoargs(47, @mylist); # 47赋给$scalar，@mylist赋给@list
&twoargs(@mylist); # @mylist的第一个元素赋给$scalar，其余的元素赋给@list

sub twoargs {
    my ($scalar, @list) = @_;
}

@myarray = (1, 2, 3, 4, 5);
&my_sub(*myarray);
sub my_sub {
    my (*subarray) = @_;
}

$foo = 26;
@foo = ("here's", "a", "list");
&testsub (*foo);

sub testsub {
    local (*printarray) = @_;
    $printarray = 61; # 当子程序执行完，主程序中的$foo的值已经成了61，而不再是26了。
}

@array1 = (1, 2, 3);
@array2 = (4, 5, 6);
&two_array_sub (*array1, *array2);
sub two_array_sub {
    my (*subarray1, *subarray2) = @_;
} 

BEGIN {
    print("Hi! Welcome to Perl!\n");
}
AUTOLOAD{
    print("subroutine $AUTOLOAD not found\n"); # 变量$AUTOLOAD即未找到的子程序名
    print("arguments passed: @_\n");
}

$fruit{"bananas"}
$number{3.14159}
$integer{-7}

#简单变量也可作为下标
$fruit{$my_fruit}

#下标为apples的元素，值为17
#下标为bananas的元素，值为9
#下标为oranges的元素，值为none
%fruit = ("apples",17,"bananas",9,"oranges","none");

#用列表给关联数组赋值时，Perl5允许使用"=>"或","来分隔下标与值，用"=>"可读性更好些
%fruit = ("apples"=>17,"bananas"=>9,"oranges"=>"none");

@fruit = ("apples",17,"bananas",9,"oranges","none");
%fruit = @fruit;

#此语句中元素次序未定义，那么数组变量@fruit可能为("grapes",11,"lemons",27)或("lemons",27,"grapes",11)。
%fruit = ("grapes",11,"lemons",27);
@fruit = %fruit;

delete ($fruit{"lime"});

%records = ("Maris", 61, "Aaron", 755, "Young", 511);
while (($holder, $record) = each(%records)) {
  # stuff goes here
}

select (MYFILE);
 $~ = "MYFORMAT";
 write;