PERLDATA 7

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PERLDATA

NAME
DESCRIPTION æè¿°
Variable names åéå
Context ä¸ä¸æ
Scalar values æ é
Scalar value constructors æ éæ°æ®æé
List value constructors åè¡¨å¼æé
Subscripts ä¸æ
Slices çæ®µ
Typeglobs and Filehandles å¨å±ç±»ååæä»¶å¥æ
SEE ALSO åè§
ä¸æçç»´æ¤äºº
ä¸æçææ°æ´æ°
ä¸ææåé¡µç¿»è¯è®¡å
è·

NAME

perldata- Perl æ°æ®ç±»å

DESCRIPTION æè¿°

Variable names åéå

$days # ç®åæ é "days"
$days[28] # æ°ç» @daysçç¬¬29ä¸ªåç´
$days{’Feb’} # åå¸ %daysç ‘Feb’ æå¯¹åºçå¼
$#days # æ°ç» @daysçæåä¸ä¸ªåç´ çç´¢å¼å¼

@days # ($days[0], $days[1],... $days[n])
@days[3,4,5] # å³ ($days[3],$days[4],$days[5])
@days{’a’,’c’} # å³ ($days{’a’},$days{’c’})

æ´ä¸ªåå¸ä»¥ ’%’ å¼å§:

%days # (key1, val1, key2, val2 ...)

å ä¸ºåéåä»¥ ’$’, ’@’, æ ’%’å¼å§, ä¿çè¯å¯¹åéæ²¡æä»ä¹å½±åãä¿çè¯å½±å çæ¯æ ç¾åæä»¶å¥æï¼å ä¸ºå®ä»¬ä¸æ¯ä»¥ç¹æ®åç¬¦åç¼å¼å§çãä½ ä¸è½ç¨“log” æ¥å½åæä»¶å¥æï¼å ä¸ºå®æ¯ä¿çè¯ï¼æç¤ºï¼ä½ å¯ä»¥ç¨ ‘open(LOG,’logfile’)’ èä¸æ¯ ‘open(log,’logfile’)’). ä½¿ç¨å¤§åçæä»¶å¥ææ¢å¢å äºå¯è¯»æ§ï¼ ååå°äºå²çªçåçãå¤§å°åæ¯ææä¹ç--“ FOO ”,“Foo”, å“foo” æ¯ä¸åçåç§°ãä»¥å- æ¯æä¸åçº¿å¼å§çåç§°å¯ä»¥åå«æ°ååä¸åçº¿ã

Context ä¸ä¸æ

æä½å¯ä»¥æ ¹æ®ä¸åçä¸ä¸æè¿åä¸åçå¼ãä¾å¦ï¼å¦æè¿æ ·åï¼

int( <STDIN> )

sort( <STDIN> )

Scalar values æ é

if ($str == 0 && $str ne "0") {
warn "That doesn’t look like a number";
}

warn "has nondigits" if /\D/;
warn "not a natural number" unless /ˆ\d+$/; # rejects -3
warn "not an integer" unless /ˆ-?\d+$/; # rejects +3
warn "not an integer" unless /ˆ[+-]?\d+$/;
warn "not a decimal number" unless /ˆ-?\d+\.?\d*$/; # rejects .2
warn "not a decimal number" unless /ˆ-?(?:\d+(?:\.\d*)?|\.\d+)$/;
warn "not a C float"
unless /ˆ([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/;

@whatever = ();
$#whatever = -1;

scalar(@whatever) == $#whatever - $[ + 1;

scalar(@whatever) == $#whatever + 1;

æäºç¨åºåä¸ºäºæç¡®èµ·è§, ä¼ä½¿ç¨æ¾å¼çè½¬æ¢:

$element_count = scalar(@whatever);

keys(%users) = 1000; # åé 1024 ç©ºé´

Scalar value constructors æ éæ°æ®æé

æ°å¼å¸¸éæä»¥ä¸æµ®ç¹åæ´æ°æ ¼å¼:

12345
12345.67
.23E-10 # a very small number
3.14_15_92 # a very important number
4_294_967_296 # underscore for legibility
0xff # hex
0xdead_beef # more hex
0377 # octal
0b011011 # binary

åç¬¦ä¸²éå¸¸ä»¥åå¼å·æåå¼å·æ¬èµ·. ä¸æ åUnix shellsä¸çå¼å·ç¸ä¼¼: åå¼å·å¯ä»¥æ¥æ¶è½¬ä¹ååé; åå¼å·ä¸å¯ä»¥ (é¤äº‘\’’ å‘\\’)). C æ ·å¼çè½¬ä¹å- ç¬¦å¯ä»¥ç¨æ¥è¾å¥æ°è¡ï¼è·³æ ¼çåç¬¦ï¼è½¬ä¹åç¬¦çåè¡¨å¯ä»¥åè§ perlop ä¸- ç“Quote and Quote-like Operators”

$Price = ’$100’; # not interpolated
print "The price is $Price.\n"; # interpolated

perl ä¸æ²¡æ double interpolationï¼å æ¤$100 ä¿æä¸åã

$who = "Larry";
print PASSWD "${who}::0:0:Superuser:/:/bin/perl\n";
print "We use ${who}speak when ${who}’s here.\n";

å¦ææ²¡æè±æ¬å·, Perlä¼å¯»æ¾ $whospeak, $who::0, å $who’s åé. åä¸¤ä¸ªæ¯ä¸åå¨ç who åä¸ç$0 å $s.

Version Strings

æ³¨æ: Version Strings (v-strings) have been deprecated. They will not be available after Perl 5.8. The marginal benefits of v-strings were greatly outweighed by the potential for Surprise and Confusion.

ç±»ä¼¼‘v1.20.300.4000’ è¿æ ·çå½¢å¼è¢«è§£éä¸ºä¸ä¸ªåç¬¦ä¸². è¿ç§å½¢å¼ç§°ä¸º v-stringsï¼æä¾äºæ´æè¯»çæ¹æ³æ¥æé å- ç¬¦ä¸²ï¼æ¯èµ·"\x{1}\x{14}\x{12c}\x{fa0}" æ´å æè¯». è¿å¨è¡¨ç¤º Unicode åç¬¦ä¸²æ¶å¾æç¨, å¨ä½¿ç¨åç¬¦ä¸²æ¯è¾å½ä»¤(‘cmp’,‘gt’,‘lt’ ç- )æ¯è¾çæ¬å·æ¶ä¹éå¸¸æç¨. å¦æå¶ä¸çç¹å·å¤äºä¸¤ä¸ª, åå¼å§ç‘v’ å¯ä»¥çç¥.

print v9786; # prints UTF-8 encoded SMILEY, "\x{263a}"
print v102.111.111; # prints "foo"
print 102.111.111; # same

è¿ç§å½¢å¼å¯ä»¥ç¨äºrequire å use ä¸ä½çæ¬æ£æ¥.“$ˆV” ç¹æ®åéä¸- çPerlçæ¬å·å°±æ¯ä»¥è¿ç§å½¢å¼ä¿åç. åè§ perlvar ä¸ç“$ˆV” æ³¨æä½¿ç¨ v-strings æ¥ä¿å IPv4 å°åæ¯ä¸å¯ç§»æ¤çï¼é¤éåæ¶ä½¿ç¨ Socket åçinet_aton()/inet_ntoa() å½æ°ã

æ³¨æä» Perl 5.8.1 å¼å§åä¸ªæ°åç v-strings (ç±»ä¼¼‘v65’) å¦æå¨‘=>’ æä½ç¬¦(éå¸¸ç¨æ¥ä» hash å¼ä¸åºåå¼ hash é®) ä¹åï¼ä¸æ¯ä¸ä¸ª v-stringsï¼èæ¯è§£éä¸ºåç¬¦ä¸² (’v65’)ãå¨ Perl 5.6.0 å° Perl 5.8.0 å®ä¸ç´æ¯ v-stringsï¼ä½æ¯è¿æ ·å¸¦æ¥äºæ´å¤æ··æ·åéè¯¯èä¸æ¯ä¼ç¹ãå¤ä¸ªæ°åç v-stringsï¼ç±»ä¼¼‘v65.66’ å65.66.67ï¼ç»§ç»æ»æ¯è¢«å½ä½ v-strings

ç¹æ®å¸¸é

ç¹æ®åé __FILE__, __LINE__, å __PACKAGE__ ä»£è¡¨å½åæä»¶å,è¡å·,ååå. å®ä»¬åªè½ä½ä¸ºåç¬çç¬¦å·æ¥ä½¿ç¨; ä¸è½ç¨äºåç¬¦ä¸²ä¸åæ. å¦ææ²¡æå½åå(ç¨‘package;’ æä»¤æ¥å®ç°), å__PACKAGE__ æ¯ä¸ä¸ªæªå®ä¹çå¼.

æ§å¶åç¬¦ ˆD å ˆZ, ä»¥å __END__ å __DATA__ åéå¯ä»¥è¡¨ç¤ºæä»¶çé»è¾ç»æ. å¶åçææ¬è¢«å¿½ç¥.

__DATA__ ä¹åçææ¬å¯ä»¥éè¿æä»¶å¥æ‘PACKNAME::DATA’ è¯»å,‘PACKNAME’ æ¯ __DATA__ æå¨çåçåç§°. å¥ææå__DATA__ åé¢çææ¬. è¯»åç»æç¨åºä¼èªå¨å³é- è¯¥å¥æ‘close DATA’. ä¸ºäºä¸ __DATA__ è¿æ²¡æåºç°ä»¥åå·²ç»åå¨çç¨åºå¼å®¹, __END__ å¨é¡¶çº§èæ¬ä¸ä¸ __DATA__ æ§è´¨ç¸å(å¨ç¨‘require’ æ‘do’ è°ç¨æ¶æ¯ä¸åç) ä¸è¿å¯ä»¥éè¿‘main::DATA’ æ¥è°ç¨å¶ä¸çåå®¹.

åè§ SelfLoader è¯¦ç»äºè§£ __DATA__, å¶ä¸è¿æä¾å. è¦æ³¨æå¨BEGIN åä¸- æ æ³è¯»åDATAå¥æ: å ä¸ºBEGIN åå¨ç¼è¯æ¶å³è¢«æ§è¡, èæ¤æ¶ __DATA__ (æ __END__) è¿æªè¢«ç¨åºçå°.

è£¸è¯

use strict ’subs’;

æ°ç»åå¹¶åéç¬¦

$temp = join($", @ARGV);
system "echo $temp";

system "echo @ARGV";

å¨æç´¢æ¨¡å¼ä¸(å¨åå¼å·åç¬¦ä¸²ä¸ä¹æ¯)æä¸ä¸ªææ··æ·ä¹å¤:‘/$foo[bar]/’ åºè¯¥æ¯‘/${foo}[bar]/’ (‘[bar]’ æ¯æ£åè¡¨è¾¾å¼çåç¬¦ç±») è¿æ¯‘/${foo[bar]}/’/ (‘[bar]’ æ¯æ°ç»@foo çä¸æ ) å¢? å¦æ@foo ä¸åå¨, é£å¾ææ¾å®åºè¯¥æ¯åç¬¦ç±». å¦æ@foo åå¨, Perl ä¼å°½åçæµ‘[bar]’ çå«ä¹, ä¸å®å ä¹æ»æ¯å¯¹ç. å¦æå®çéäº, æèä½ æ¯è¾åæ§, ä½ å¯ä»¥ä½¿ç¨è±æ¬å·.

here-document çè¯æ³å·²ç»è¢«ç§»å¨å° perlop ä¸ç“Quote and Quote-like Operators”

List value constructors åè¡¨å¼æé

(LIST)

@foo = (’cc’, ’-E’, $bar);

å°åè¡¨èµç»æ°ç»@foo, ä½æ¯

$foo = (’cc’, ’-E’, $bar);

@foo = (’cc’, ’-E’, $bar);
$foo = @foo; # $foo gets 3

åè¡¨çæåå¯ä»¥è¾å¥éå·, æä»¥è¿æ ·ä¹æ¯æ£ç¡®ç:

@foo = (
1,
2,
3,
);

@sauces = <<End_Lines =˜ m/(\S.*\S)/g;
normal tomato
spicy tomato
green chile
pesto
white wine
End_Lines

(@foo,@bar,&SomeSub,%glarch)

åæ¬@foo,@barçæ¯ä¸ä¸ªåç´ ,åæ¬å½æ° SomeSub è¿åå¼åè¡¨çæ¯ä¸ä¸ªåç´ , åæ¬ %glarch çæ¯ä¸ä¸ªåå¼å¯¹. è¦æ³ä½¿ç¨ä¸åæçåè¡¨, å¯ä»¥åè§ perlref

ç©ºåè¡¨å¯ä»¥è¡¨ç¤ºä¸º(). å¨åè¡¨ä¸æå¥ç©ºåè¡¨æ²¡ææä¹. ((),(),()) ä¸()ç¸å. åæ ·, åæä¸ä¸ªç©ºæ°ç»ä¹æ²¡ææä¹.

# Stat returns list value.
$time = (stat($file))[8];

# SYNTAX ERROR HERE.
$time = stat($file)[8]; # OOPS, FORGOT PARENTHESES

# Find a hex digit.
$hexdigit = (’a’,’b’,’c’,’d’,’e’,’f’)[$digit-10];

# A "reverse comma operator".
return (pop(@foo),pop(@foo))[0];

å¯ä»¥ç»åè¡¨èµå¼, å½ç¶åè¡¨ä¸çæ¯ä¸ªåç´ å¿é¡»åæ³æè¡:

($a, $b, $c) = (1, 2, 3);

($map{’red’}, $map{’blue’}, $map{’green’}) = (0x00f, 0x0f0, 0xf00);

($dev, $ino, undef, undef, $uid, $gid) = stat($file);

$x = (($foo,$bar) = (3,2,1)); # set $x to 3, not 2
$x = (($foo,$bar) = f()); # set $x to f()’s return count

$count = () = $string =˜ /\d+/g;

$count = $string =˜ /\d+/g;

æåä¸ä¸ªåç´ å¯ä»¥æ¯æ°ç»æåå¸:

($a, $b, @rest) = split;
my($a, $b, %rest) = @_;

åå¸å¯ä»¥ç¨å«æåå¼å¯¹çåè¡¨æ¥åå§å:

# same as map assignment above
%map = (’red’,0x00f,’blue’,0x0f0,’green’,0xf00);

%map = (
red => 0x00f,
blue => 0x0f0,
green => 0xf00,
);

æèåå§ååå¸çå¼ç¨:

$rec = {
witch => ’Mable the Merciless’,
cat => ’Fluffy the Ferocious’,
date => ’10/31/1776’,
};

or for using call-by-named-parameter to complicated functions:

$field = $query->radio_group(
name => ’group_name’,
values => [’eenie’,’meenie’,’minie’],
default => ’meenie’,
linebreak => ’true’,
labels =>\%labels
);

Subscripts ä¸æ

@myarray = (5, 50, 500, 5000);
print "Element Number 2 is", $myarray[2], "\n";

æ°ç»ä¸æ ä» 0 å¼å§ãè´å¼ä¸æ è¿åä»å°¾é¨å¼å§æ°çå¼ãå¨æä»¬çä¾åä¸- ï¼$myarray[-1] å°æ¯ 5000,$myarray[-2] æ¯ 500ã

%scientists =
(
"Newton" => "Isaac",
"Einstein" => "Albert",
"Darwin" => "Charles",
"Feynman" => "Richard",
);

print "Darwin’s First Name is ", $scientists{"Darwin"}, "\n";

Slices çæ®µ

$whoami = $ENV{"USER"}; # one element from the hash
$parent = $ISA[0]; # one element from the array
$dir = (getpwnam("daemon"))[7]; # likewise, but with list

($him, $her) = @folks[0,-1]; # array slice
@them = @folks[0 .. 3]; # array slice
($who, $home) = @ENV{"USER", "HOME"}; # hash slice
($uid, $dir) = (getpwnam("daemon"))[2,7]; # list slice

@days[3..5] = qw/Wed Thu Fri/;
@colors{’red’,’blue’,’green’}
= (0xff0000, 0x0000ff, 0x00ff00);
@folks[0, -1] = @folks[-1, 0];

ä¸é¢çæä½ä¸ä¸åè¯å¥çä»·:

($days[3], $days[4], $days[5]) = qw/Wed Thu Fri/;
($colors{’red’}, $colors{’blue’}, $colors{’green’})
= (0xff0000, 0x0000ff, 0x00ff00);
($folks[0], $folks[-1]) = ($folks[-1], $folks[0]);

foreach (@array[ 4 .. 10 ]) { s/peter/paul/ }

foreach (@hash{qw[key1 key2]}) {
s/ˆ\s+//; # trim leading whitespace
s/\s+$//; # trim trailing whitespace
s/(\w+)/\u\L$1/g; # "titlecase" words
}

@a = ()[1,0]; # @a has no elements
@b = (@a)[0,1]; # @b has no elements
@c = (0,1)[2,3]; # @c has no elements

ä½æ¯:

@a = (1)[1,0]; # @a has two elements
@b = (1,undef)[1,0,2]; # @b has three elements

while ( ($home, $user) = (getpwent)[7,0]) {
printf "%-8s %s\n", $user, $home;
}

Typeglobs and Filehandles å¨å±ç±»ååæä»¶å¥æ

*this = *that;

ä½¿å¾$this æä¸º $thatçå«å, @this æä¸º @thatçå«å,%this æä¸º %thatçå«å, &this æä¸º &thatçå«å, çç. ä½¿ç¨å¼ç¨ä¼æ´å®å¨. è¿æ ·:

local *Here::blue =\$There::green;

ææ¶ä½¿ $Here::blue æä¸º $There::greençå«å, ä½ä¸ä¼ä½¿ @Here::blue æä¸º @There::greençå«å, ä¹ä¸ä¼ä½¿ %Here::blue æä¸º %There::greençå«å, çç. åè§ perlmod ä¸ç Symbol Tables æå¤ä¸ªä¾å. çèµ·æ¥å¯è½æäºæªå¼, ä¸è¿è¿å´æ¯æ´ä¸ªimport/exportç³»ç»çåºç¡.

$fh = *STDOUT;

æèä½¿ç¨çæ£çå¼ç¨, è±¡è¿æ ·:

$fh =\*STDOUT;

åè§ perlsub æå³äºé´æ¥å¥æçå¤ä¸ªä¾å.

sub newopen {
my $path = shift;
local *FH; # not my!
open (FH, $path) or return undef;
return *FH;
}
$fh = newopen(’/etc/passwd’);

ææè½åå»ºæä»¶å¥æçå½æ° (open(), opendir(), pipe(), socketpair(), sysopen(), socket(), å accept()) ,å¨ä¼ éç»å®ä»¬çå¥ææ¯æ éæ¶,ä¼èªå¨åå»ºä¸ä¸ªå¿åå¥æ. è¿ä½¿å¾è±¡open(my $fh, ...) å open(local $fh,...) è¿æ ·çç»æå¯ä»¥åå»ºä¸ä¸ªå¨è¶åºèå´æ¶å¯ä»¥èªå¨å³é- çå¥æ,å¦ææ²¡æå¦å¤çå¯¹å®ä»¬çå¼ç¨çè¯. è¿å¤§å¤§åå°äºå¨å±ç±»åçä½¿ç¨,å½éè¦æå¼ä¸ä¸ªå¯ä»¥å°å¤ä½¿ç¨çå¥ææ¶, å¯ä»¥è¿æ ·åï¼

sub myopen {
open my $fh, "@_"
or die "Can’t open ’@_’: $!";
return $fh;
}

{
my $f = myopen("</etc/motd");
print <$f>;
# $f implicitly closed here
}

æ³¨æå¦æä½¿ç¨äºåå§åçæ éï¼é£ä¹ç»æä¼æä¸åï¼‘my $fh=’zzz’; open($fh, ...)’ ä¸‘open( *{’zzz’}, ...)’ çä»·ã‘use strict ’refs’’ ç¦æ¢äºè¿æ ·åã

å¦ä¸ä¸ªåå»ºå¿åå¥æçæ¹æ³æ¯ç¨Symbol æ¨¡åæIO::Handle æ¨¡åæè¯¸å¦æ¤ç±»çä¸è¥¿. These modules have the advantage of not hiding different types of the same name during the local(). å¨ open() in the perlfunc manpage çææ«æä¸ªä¾å- .(è¯èæ³¨:è¯´å®è¯,å¯¹å¿åå¥ææç°å¨ä¹æ¯ä¸å¤´é¾æ°´,ç¿»è¯çä¸å½ä¹å¤,è¯·é«ææåº.)

ä¸æçç»´æ¤äºº

redcandle <redcandle51@nospam.chinaren.com>

ä¸æçææ°æ´æ°

2001å¹´12æ4æ¥ææäº

ä¸ææåé¡µç¿»è¯è®¡å

http://cmpp.linuxforum.net

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æ¬é¡µé¢ä¸æçç±ä¸æ man æåé¡µè®¡åæä¾ã
ä¸æ man æåé¡µè®¡åï¼https://github.com/man-pages-zh/manpages-zh

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