====== - perl语法速查 ======


===== - 技巧文章 =====
{{indexmenu>:linux:perl}}





===== - perl单行命令 =====

<code bash>
# linux里面可以用 ''
perl -e "print 0;"
perl -E "print 0;"

perl -e "$i = int(rand(100000)); print $i"    # 单行命令产生随机数
</code>

===== - 正则表达式 =====

==== - 匹配多次 ====

/a{5,15}/将匹配5 个到15 个a 中的任意一个（包括 5，和15）

/(fred){3,}/将在一行中有 3 个或者更多个 fred

/\w{8}/将严格的匹配 8 个word

星号(*)等同于{0,}，表示 0 个或多个。

加号(+)等同于{1,}，表示 1 个或多个。

而问号(?)则等同于{0,1}。


==== - 匹配非 ====
[^def]将匹配上这三个字符中之外的任意单个字符

===== - number =====

<code perl>
浮点数
1.25
255.000
255.0
7.25e45  # 7.25 times 10 to the 45th power (a big number)
–6.5e24  # negative 6.5 times 10 to the 24th
         # (a big negative number)
–12e–24  # negative 12 times 10 to the –24th
         # (a very small negative number)
–1.2E–23 # another way to say that the E may be uppercase

整数
0
2001
–40
255
61298040283768
61_298_040_283_768    可自动识别下划线，与上面数字相同，方便人眼观察。

0xff       # FF hex, also 255 decimal    十六进制数

</code>

===== - list =====

<code perl>

@ar = ();
push @ar, $xx;
push @ar, $yy;  # 将变量圧到数组最后
$aa = shift @ar; # 取出数组第一个元素给变量，数组长度减1
$bb = pop $ar;   # 取出数组最后一个元素给变量，数组长度减1
unshift @ar, @add; #将add数据里面的数据移入ar前面

</code>


<code>
@a = (1, 2, 3);
$a = (21, 22, 33);
print "a = $a\n"; # 结果为33,不清楚为什么为这样，不要将数组直接给普通变量
print "a = @a\n";

输出：
a = 33
a = 1 2 3
</code>

<code perl>
@a = ((1, 2), (3, 4));
for $i (@a) {
    print "$i\n";
}

输出：
1
2
3
4
</code>
===== - hash =====

<code perl>

%hash = ();

$hash{"a"} = 1;
$hash{"b"} = 2;
$hash{"c"} = 3;

for $key (keys %hash) {
	$value = $hash{$key};
	print "key = $key, value = $value\n";
}

delete $hash{"a"};


for $key (sort keys %hash) {
	$value = $hash{$key};
	print "key = $key, value = $value\n";
}


my @descending = reverse sort { $a <=> $b } @some_numbers;
my @descending = sort {$b <=> $a } @some_nubmers;

for $key (sort {$hash{$a} <=> $hash{$b} keys %hash) {
#按值的升序排列
}
for $key (sort {$hash{$a}->{idx} <=> $hash{$b}->{idx} keys %hash) {
#按ref值的升序排列
}
for $key (sort {$hash{$b} <=> $hash{$a} keys %hash) {
#按值的降序排列
}
for $key (sort {$hash{$b}->{idx} <=> $hash{$a}=>{idx} keys %hash) {
#按ref值的降序排列
}

</code>



===== - reference =====
==== - ref for array ====

<code perl>

@a = (1, 2, 3);
print "@a\n";    # result:  1 2 3

%hash = ();
$hash{"a"} = \@a; # reference of @a

$ref = $hash{"a"};
print "$ref\n";     # result: ARRAY(0x25d7338)
print "@$ref\n";    # result:  1 2 3
</code>


<code perl>
@a = (1, 2, 3);
@b = (4, 5, 6);
@c = (7, 8, 9);
@o = (\@a, \@b); # 数组放进数组
print "@o\n";
push @o, \@c;
for $i (@o) {
    print "@$i\n";
}
输出：
ARRAY(0x654b20) ARRAY(0x65f568)
1 2 3
4 5 6
7 8 9
</code>
==== - ref for hash ====
<file perl t.pl>
sub new_block {
    return {
        name => "",
        id => "",
        blk => {},
    }
}
sub new_hash {
    return {
    }
}

$blk = &new_block;
$blk->{name} = "hello";
$blk->{id} = 1;

$blk2 = &new_hash;
$blk2->{a} = "a0";
$blk2->{b} = "b0";

$blk->{blk} = $blk2;


print "-------------\n";
foreach $key (sort keys %{$blk}) {
    print "$key   $blk->{$key}\n";
}
print "\n";

print "-------------\n";
foreach $key (sort keys %{$blk->{blk}}) {
    print "$key   $blk->{blk}->{$key}\n";
}
print "\n";
</file>

运行结果：
<code>
D:\>perl t.pl
-------------
blk   HASH(0x100a950)
id   1
name   hello

-------------
a   a0
b   b0
</code>

==== - hash包array ====
<code perl>
@a = (1, 2, 3);
@b = (11, 22, 33);
$hash{a} = \@a;
$hash{b} = \@b;
foreach $key (sort keys %hash) {
    $ar_ref = $hash{$key};
    for $i (@{$ar_ref}) {
        print "$i\n";
    }
}
$c = @{$hash{b}}[2]; #输出数组b的第2个值
print "c = $c\n";


输出：
1
2
3
11
22
33
c = 33
</code>


==== - array包hash ====
<code perl>
$hash_a{a} = 1;
$hash_b{a} = 2;
@a = (\%hash_a, \%hash_b);
for $i (@a) {
    print "$i\n";
}
for $i (@a) {
    print "$i->{a}\n";
}

输出：
HASH(0x6efcc0)
HASH(0x6efd20)
1
2
</code>

<code perl>
$hash_a{a} = 1;
$hash_b{a} = 2;
@a = (%hash_a, %hash_b);
for $i (@a) {
    print "$i\n";
}

输出：
a
1
a
2
</code>

<code perl>
@ar = ();
sub new_hash {
    return {}
}
for ($i=0; $i<3; $i++) {
    $hash = &new_hash;
    push @ar, $hash;
    $hash->{value} = $i;
    $hash->{value2} = "value_$i";
}
for $i (@ar) {
    print "$i\n";
    print "$i->{value}\n";
    print "$i->{value2}\n";
}
输出：
HASH(0x1e9520)
0
value_0
HASH(0x24d42b8)
1
value_1
HASH(0x24d4390)
2
value_2
</code>
===== - 循环 =====
==== - for ====
<code perl>
@ar = (1, 2);

for ($i=0; $i<2; $i++) {
    print "$ar[$i]\n";
}

foreach $i (@ar) {
    print "$i\n";
}

for $i (@ar) {
    print "$i\n";
}

#输出
PS D:\> perl t.pl
1
2
1
2
1
2
</code>


===== - 字符串操作 =====

<code perl>
"hello" . "world"       # same as "helloworld"
"hello" . ' ' . "world" # same as 'hello world'
'hello world' . "\n"    # same as "hello world\n"

"fred" x 3       # is "fredfredfred"
"barney" x (4+1) # is "barney" x 5, or "barneybarneybarneybarneybarney"
5 x 4.8          # is really "5" x 4, which is "5555"
</code>

===== - 文件和目录操作 =====


==== - 读写文件 ====


<code perl>
#open读文件
open(my $fh, "<", "input.txt")
  or die "Can't open < input.txt: $!";
and for writing:

#open写文件
open(my $fh, ">", "output.txt")
  or die "Can't open > output.txt: $!";

#close文件
close($handle)
  || warn "close failed: $!";
</code>



<code perl>
#写文件
print $fh "hello\n";


#读文件
while ($line =<$fh>) {
  print $line;
}
</code>

==== - readdir ====

<code perl>
# 读目录
my $dir_to_process = '/etc';
opendir my $dh, $dir_to_process or die "Cannot open $dir_to_process: $!";
foreach $file (readdir $dh) {
  print "one file in $dir_to_process is $file\n";
}
closedir $dh;
</code>


==== - 删除文件 unlink ====
<code perl>
unlink 'slate', 'bedrock', 'lava';
unlink qw(slate bedrock lava);
unlink glob '*.o';
</code>

==== - rename ====
<code perl>
rename 'old', 'new';
</code>


==== - mkdir rmdir ====
<code perl>
mkdir 'fred', 0755
rmdir $temp_dir;
</code>


==== - chmod ====
<code perl>
chmod 0755, 'fred', 'barney';
</code>

==== - chown ====
<code perl>
chown $user, $group, glob '*.o';
</code>


==== - 获取当前目录PATH ====
有两种方法：
<code perl>
use Cwd;
my $dir = getcwd;
#$dir中即为当前目录的完整路径信息。
</code>

<code perl>
my $dir = $ENV{'PWD'};
#ENV是一个散列，用于存放环境变量。PWD是Linux的环境变量，表示当前所在目录。
</code>
===== - perl处理excel =====

==== - 读excel ====

<code perl>
use Spreadsheet::ParseExcel;
use Spreadsheet::ParseXLSX;

if (scalar @ARGV <1) {
    print "usage: perl get_feedthrough.pl xxx.xlsx\n";
    exit 0;
}
$ifile = shift @ARGV;

# 创建一个解析器对象
if ($ifile =~ /xlsx/) {
    $parser = Spreadsheet::ParseXLSX->new(); # for xlsx
} else {
    $parser = Spreadsheet::ParseExcel->new(); # for xls
}


# 打开Excel文件并创建一个工作簿对象
$workbook = $parser->parse($ifile);

# 获取工作表对象
$worksheet = $workbook->worksheet(0);

# 读取单元格数据
$cell = $worksheet->get_cell(2, 1);  # 索引值从0开始
if ($cell == under) {
    print "cell = under\n"; # 表格无内容
} else {
    $cell_value = $worksheet->get_cell(2, 1)->value();
    print "Cell A1: $cell_value\n";
}
</code>


===== - perl处理json =====

<code perl [enable_line_numbers="true"]>
use JSON;
use Data::Dumper;
local $Data::Dumper::Sortkeys = 1;




##########     use JSON; # imports encode_json, decode_json, to_json and from_json.
##########      
##########     # simple and fast interfaces (expect/generate UTF-8)
##########      
##########     $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
##########     $perl_hash_or_arrayref  = decode_json $utf8_encoded_json_text;
##########      
##########     # OO-interface
##########      
##########     $json = JSON->new->allow_nonref;
##########      
##########     $json_text   = $json->encode( $perl_scalar );
##########     $perl_scalar = $json->decode( $json_text );
##########      
##########     $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing



my %rec_hash = ('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5);
my $json = encode_json \%rec_hash;
print "$json\n";

$ha_ref = decode_json $json;

print Dumper($json);
print Dumper($ha_ref);


# using custom sort function
# local $Data::Dumper::Sortkeys = sub { [ sort keys %{+shift} ] };

print Dumper {
    car => {
        '10' => 'y',
        '11' => 'y',
        '12' => 'y',
        '13' => 'y'
    },
    bus => {
        '10' => 'y',
        '11' => 'y',
        '12' => 'y',
        '13' => 'y'
    },
    tr => {
        '10' => 'y',
        '11' => 'y',
        '12' => 'y',
        '13' => 'y'
    }
}

</code>


==== UTF8与GBK的转换 ====

<code perl>
use Encode;
gbk转uft-8：
$line = encode("utf-8",decode("gbk",$line));
或
$line = encode_utf8(decode("gbk",$line));
utf-8转gbk：
$line = encode("gbk", decode("utf8", $line));
uft-8转gb2312：
$line = encode("gb2312", decode("utf8", $line));

</code>