jasmine214--love

1.25 255.000 255.0 7.25e45 #7.25x10 的 45 次方(一个大整数) -6.5e24 # -6.5x10 的 24 次方(一个大的负数) -12e-24 #- -12x10 的-24 次方(很小的负数) -1.2E-23 #指数符号可以大写(E) 

0 2001 -40 255 61298040283768 

61_298_040_283_768 

0377 #八进制数字 377,等同于十进制数字 255 0xff #十六进制数字 FF,等同于十进制数字 255 0b11111111 #等同于十进制数字 255 

0x1377_0B77 0x50_65_72_7C 

2+3 #2+3,5 5.1-2.4 #5.1-2.4,2.7 3*12 #3*12,36 14/2 #14/2,7 10.2/0.3 #10.2/0.3,34 10/3 #通常是浮点除,3.33333... ... 

'fred' #四个字符:f,r,e,d '' #空字符(没有字符) 'hello\n' '\'\\' #单引号(')跟着反斜线(\)字符串 

"barney" #等同于 'barney' "hello world\n" #hello world,换行 

"hello"."world" # 同于 "helloworld" "hello".''."world" # 同于 "hello world" 'hello world'."\n" # 同于 "hello world\n" 

"fred" x 3 # "fredfredfred" 5 x 4 # 等于 "5" x 4, "5555" 

"12" * "3" # * 操作符需要数字，所以结果为 36 "12fred34" * " 3" # 结果仍然是 36 , 后面的非数字部分和前面的空格都过滤掉。 

"Z" . 5 * 7 # 等于 "Z".35，或 "Z35" 

$ perl -w perl程序 # 命令行执行警告 #!/usr/bin/perl -w # 源代码中使用警告 

$a_very_long_variable_that_ends_in_1 $a_very_long_variable_that_ends_in_2 

$fred = 17; $barney = "hello"; $barney = $fred + 3;# 将$fred 的值加上三赋给$barney (20) $barney= $barney*2;#将变量$barney 乘 2 再赋给$barney (40) 

$fred = $fred + 5; #没有用二元赋值操作符 $fred+=5; #利用二元赋值操作符 $barney = $barney*3; $barney*=3; $str = str . ""; #$str 后接空格; $str .= ""; #同上 

print "hello world\n"; #输出 hello world,后接换行符 print "The answer is", 6*7, ".\n" 

$meal = "brontosaurus steak" ; $barney = "fred ate a $meal"; $barney = 'fred ate a'.$meal; # 同上 

if ($name gt 'fred') { print "$name’comes after 'fred' in sorted order.\n"; } 

$text = "a line of text\n"; # 也可以由<STDIN>输入 chomp($text); #去掉换行符(\n)。 

chomp ($text = <STDIN>); #读入,但不含换行符 

$food = <STDIN>; $betty = chomp $food; #得到值 1 

$count = 0; while ($count < 10) { $count + = 2; print "count is now $count\n"; } 

$madonna = <STDIN>; If ($defined ($madonna)){ print "The input was $madonna"; } else { print "No input available!\n; } 

$madonna = undef ; #同$madonna 从未被初始化一样。 

#!/usr/bin/env perl -w $fred[0] = "yabba"; $fred[1] = "dabba"; $fred[2] = "doo"; print @fred; #print @fred."\n"; 

qw ! fred barney betty wilma dino ! qw# fred barney betty wilma dino # #有些像注释 qw( fred barney betty wilma dino ) ... 

($fred, $barney, $dino) = ("flintstone", "rubble", undef); ($fred, $barney) = qw <flintstone rubble slate granite>; #两个值被忽略了 ($rocks[0],$rocks[1],$rocks[2],$rocks[3]) = qw/talc mica feldspar quartz/; 

@rocks = qw / bedrock slate lava /; @tiny = (); #空表 @giant = 1..1e5; #包含 100,000 个元素的表 @stuff = (@giant, undef, @giant); #包含 200,001 个元素的表 @dino = "granite"; @quarry = (@rocks, "crushed rock", @tiny, $dino); 

@array = 5..9; $fred = pop(@array); #$fred 得到 9,@array 现在为(5,6,7,8) $barney = pop @array; #$barney gets 8, @array 现在为(5,6,7) pop @array; #@array 现在为(5,6)(7 被丢弃了) 

push(@array,0); #@array 现在为(5,6,0) push @array,8; #@array 现在为(5,6,0,8) push @array,1..10; #@array 现在多了 10 个元素 @others =qw/9 0 2 1 0 /; push @array,@others; #@array 现在又多了 5 个元素(共有 19 个) 

@array = qw# dino fred barney #; $m = shift (@array); #$m 得到 "dino"， @array 现在为 ("fred", "barney") $n = shift @array; #$n 得到 "fred", @array 现在为 ("barney") shift @array; #@array 现在为空 $o = shift @array; #$o 得到 undef, @arry 仍为空 unshift(@array,5); #@array 现在为(5) unshift @array,4; #@array 现在为(4,5) @others = 1..3; unshift @array, @others; #array 现在为(1,2,3,4,5) 

@rocks = qw{ flintstone slate rubble }; print "quartz @rocks limestone\n"; #输出为 5 种 rocks 由空格分开 

foreach $rock (qw/ bedrock slate lava /) { print "One rock is $rock.\n" ; #打印出 3 种 rocks } 

foreach(1..10){ #使用默认的变量$_ print "I can count to $_!\n"; } 

$_ = "Yabba dabba doo\n"; print; # 打印出默认变量 $_ 

@fred = 6 .. 10; @barney = reverse (@fred); #得到 10,9,8,7,6 @wilma = reverse 6 . .10; #同上,没有使用额外的数组 @fred = reverse @fred; #将逆转过的字符串存回去 

@rocks = qw/ bedrock slate rubble granite /; @sorted = sort(@rocks); #得到 bedrock, granite, rubble, slate 

42 + something #something 必须是标量 sort something #something 必须是列表 

@people = qw( fred barney betty ); @sorted = sort @people; #列表内容： barney , betty, fred $number = 42 + @people; #标量内容：42+3,得到 45 

@backwards = reverse qw / yabba dabba doo /; #返回 doo, dabba, yabba $backwards = reverse qw/ yabba dabba doo /; #返回 oodabbadabbay 

@fred = 6*7; @barney = "hello" . '' . "world"; 

@rocks = qw(talc quartz jade obsidian); print "How many rocks do you have?\n; print "I have " @rocks, "rocks!\n"; # 错误,输出 rocks 的名字 print "I have " scalar @rocks, "rocks!\n; # 正确,输出其数字 

@lines = <STDIN>; #将输入读入列表 context 中 chomp (@lines = <STDIN>); #读入所有的行,不包括换行符 

sub marine { $n + = 1; #全局变量$n print "Hello, sailor number $n!\n"; } 

&marine; #输出 Hello, sailor number 1! &marine; #输出 Hello, sailor number 2! &marine; #输出 Hello, sailor number 3! &marine; #输出 Hello, sailor number 4! 

$n = &max(10,15); # 此子程序有 2 个参数 

 sub max{ if($_[0] > $_[1]) { $_[0]; } else { $_[1]; } } 

foreach (1..10){ my($square) = $_*$_; #本循环中的私有变量 print "$_ squared is $squrare.\n"; } 

my ($num) = @_; # 列表 context, 同($sum) = @_; my $num = @_; # 标量 context,同$num = @_; 

use strict; #迫使采用更严格的检测 

my @cards = shuffle(@deck_of_cards); # &是不必要的 

$line = <STDIN>; #读入下一行; chomp($line); #去掉结尾的换行符 chomp($line=<STDIN>) #同上,更常用的方法 

while (defined($line = <STDIN>)) { print "I saw $line"; } 

$n = 0; while (defined($line = <>)) { $n += 1; chomp($line); print "$n $line\n"; } 

while (<>) { chomp; print "It was $_ that I saw!\n"; } 

print @array; #打印出元素的列表 print "@array"; #打印一个字符串(包含一个内插的数组) 

printf "Hello, %s : your password expires in %d days!\n", $user, $days_to_die; printf "%6f\n" 42; # 输出为 ○○○○ 42 (○此处指代空格) printf "%23\n",2e3+1.95; # 2001 

my @items = qw( wilma dino pebbles ); my $format = "The items are:\n". ("%10s\n" x @items); printf $format, @items; 

printf "The items are:\n". ("%10s\n"x @items), @items; 

open CONFIG, "dino" ; open CONFIG, "<dino" ; open BEDROCK, ">fred" ; open LOG, ">>logfile" ; 

open CONFIG, "<", "dino"; open BEDROCK, ">", $file_name; open LOG, ">>", &logfile_name(); 

close BEDROCK; 

if (!open LOG, ">>logfile") { die "Cannot create logfile:$!"; } 

if (!open PASSWD, "/etc/passwd") { die "How did you get logged in?($!)"; } while (<PASSWD>) { chomp; ... } 

$hash {$some_key} 

%some_hash = ("foo",35, "bar", 12.4, 2.5, "hello", "wilma", 1.72e30, "betty", "bye\n"); 

@array_array = %some_hash; 

%new_hash = %old_hash; %inverse_hash = reverse %any_hash; 

my %last_name = ( "fred” => "flintstone", "dino" => undef, "barney" => "rubble", "betty" => "rubble", ); 

my %hash = ("a" => 1, "b" => 2, "c" => 3); my @k = keys %hash; my @v = values %hash; 

while (($key, $value) = each %hash) { print "$key => $value\n"; } 

if (exists $books{$dino}) { print "Hey, there's a libaray card for dino!\n"; } 

my $person = "betty"; delete $books{$person}; # 将$person 的借书卡删除掉 

$_ = "yabba dabba doo"; if (/abba/) { print "It matched!\n"; } 

. ? + * 

/fred+/ # 只能匹配 fredddddd 等 /(fred)+/ # 能匹配 fredfredfred 等 /(fred)*/ # 可以匹配 "hello,world"，因为 * 是匹配前面的 0或多次 

/fred|barney|betty/ /fred( |\t)+barney/ 

\d == [0-9] \w == [A-Za-z0-9_] \s == [\f\t\n\r] # 格式符(form-feed)、制表符(tab)、换行符、回车 

\D == ［^\d] \W == [^\w] \S == [^\s] 

[\d\D] # 任何数字和任何非数字，可以匹配所有字符！比如 . 是不能匹配所有字符的 [^\d\D] # 无用 

if (/yes/i) { #大小写无关 print "In that case, I recommend that you go bowling.\n"; } 

$_ = "I saw Barney\ndown at the bowing alley\nwith Fred\nlast night.\n; if (/Barney.*Fred/s) { print "That string mentions Fred after Barney!\n"; } 

/-?\d+\.?\d*/ # 这是什么含义? / -? \d+ \.? \d* /x # 要好些 

/ -? #可选的负号 d+ #小数点前一个或多个十进制数字 \.? #可选的小数点 \d* #小数点后一些可选的十进制数字 /x #模式结束 

if (/barney.*fred/is/){ # /i 和/s print "That string mentions Fred after Barney!\n"; } 

^ 开头 $ 结尾 

/^\s*$/ # 匹配空行 

my $some_other = "I dream of betty rubble."; if ($some_other =~ /\brub/) { print "Aye, there's the rub.\n"; } 

my $likes_perl = <STDIN> =~ /\byes\b/i; 

$_ = "Hello there, neighbor"; if (/\s(\w+),/) { #空格和逗号之间的词 print "The word was $1\n"; } 

$& # 整个被匹配的部分 $` # 匹配部分的前一部分存放在$`之中 $' # 后一部分被存到$' 

$_ = "He's out bowling with Barney tonight."; s/Barney/Fred/; # Barney 被 Fred 替换掉 print "$_\n"; #接上例:现在 $_ 为 "He's out bowling with Fred tonight." s/Wilma/Betty/; # 用 Wilma 替换 Betty(失败) s/with (\w+)/agaist $1's team/; print "$_\n"; # 为 "He's out bowling against Fred's team tonight."; 

$_ = "home, sweet home!"; s/home/cave/g; print "$_\n"; # "cave, sweet cave!" 

$_ = "Input data\t may have extra whitespace."; s/\s+/ /g; # 现在是 "Input data may have extra whitespace." 

s/^\s+//; #将开头的空白去掉 s/\s+$//; #将结尾的空白去掉 s/^\s+|\s+$//g; #将开头,结尾的空白去掉 

s#^https://#http://#; 

s{fred}{barney}; s[fred](barney); s<fred>#barney#; 

s#wilma#Wilma#gi; # 将所有的 WilmA,或者 WILMA 等等,由 Wilma 替换掉 s{_ _END_ _.*}{ }s; # 将 END 标记及其后面的行去掉 

$file_name =~ s#^.*###s; # 将$file_name 中所有的 Unix 类型的路径去掉 

$_ = "I saw Barney with Fred."; s/(fred|barney)/\U$1/gi; # $_ 现在是 "I saw BARNEY with FRED." 

s/(fred)|barney/\L$1/gi; #$_现在是 "I saw barney with fred." 

s/(\w+) with (\w+)/\U$2\E with $1/I; # $1 现在是 "I saw FRED with barney." 

s/ (fred|barney)/\u$1/ig; #$_现在是 "I saw FRED with Barney." 

s/(fred|barney)/\u\L$1/ig; #$_现在为 "I saw Fred with Barney." 

print "Hello, \L\u$name\E, would you like to play a game?\n"; 

@fields = split /separtor/, $string; 

@fields = split /:/, "abc:def:g:h"; # 返回 ("abc", "def", "g", "h") 

my $some_input = "This is a \t test.\n"; my @args = split /\s+/, $some_input; # ("This", "is", "a", "test." ) 

my @fields = split; # 同 split /\s+/, $_; 

my $result = join $glue, @pieces; 

my $x = join ":", 4, 6, 8, 10, 12; #$x 为 "4:6:8:10:12" 

$_ = "Hello there, neighbor!"; my($first, $second, $third) =/(\S+) (\S+), (\S+)/; print “$second is my $third\n” ; 

my $text = "Fred dropped a 5 ton granite block on Mr. Slate"; my @words = ($text =~ /([a-z]+)/ig); print "Result: @words\n"; #Result: Fred dropped a ton granite block on Mr slate 

my $data = "Barney Rubble Fred Flintstone Wilma Flintstone"; my %last_name = ($data =~ / (\w+)\S+(\w+)/g); 

+ --> /fred.+?barney/ * --> s#<BOLD>(.*?)</BOLD>#$1#g; {5,10}? {8,}? ? --> ?? 

$ perl –p –i.bak –w –e 's/Randall/Randal/g' fred*.dat 

while(<>) { print; } 

unless ($fred =~ /^[A-Z_]\w*$/i) { print "The value of \$fred doesn't look like a Perl identifier name.\n"; } 

if ($fred =~ /^[A-Z_]\w*$/i) { #什么也不做 } else { print "The value of \$fred doesn't look like a Perl identifier name.\n"; } 

unless ($mon =~ /^Feb/) { print "This month has at least thirty days.\n"; } else { print "Do you see what's going on here?\n"; } 

until ($j > $i) { $j *= 2; } 

print "$n is a negative number.\n" if $n<0; 

if ($n < 0) { print "$n is a negative number.\n"; } 

&error ("Invalid input") unless &valid($input); $i *= 2 unitl $i > $j; print "", ($n += 2) while $n <10; &greet($_) foreach @person; 

while(condition) { body; body; body; } 

{ body; body; body; } 

{ print "Please enter a number:"; chomp(my $n = <STDIN>); my $root = sqrt $n; #计算平方根 print "The square root of $n is $root.\n"; } 

my @people = qw{ fred barney fred Wilma dino barney fred pebbles}; my %count; #新的空的 hash $count{$_}++ foreach @people; #根据情况创建新的 keys 和 values 

for (initialization; test; increment) { body; body; } 

for (1..10) { #实际上是 foreach 循环,从1到10 print "I can count to $_!\n"; } 

#输出所有出现 fred 的行,直到遇见 _ _END_ _标记 while(<STDIN>){ if(/_ _ END_ _/){ #这个标记之后不会有其它输入了 last; }elsif(/fred/){ print; } } ##last 跳转到这里## 

# 输入测试 my @words = qw{ fred barney pebbles dino Wilma betty }; my $errors = 0; foreach(@words){ ##redo 跳到这里## print "Type the word '$_' : "; chomp(my $try = <STDIN>); if($try ne $_){ print "sorry -- That's not right.\n\n"; $errors++; redo; #跳转到循环顶端 } } print "You've completed the test, with $errors errors.\n"; 

LINE: while(<>){ foreach (split){ last LINE if /_ _END_ _/; # 退出 LINE 循环 ... } } 

my $last_name = $last_name{$someone} || '(No last name)'; 

Express ? if_true_expr : if_false_expr 

my $size = ($width < 10 ) ? "small": ($width < 20) ? "medium": ($width < 50) ? "large": "extra_large"; #default 

die "Oops! A file called '$filename' already exists.\n" if -e $filename; 

warn "Config file is looking pretty old!\n" if -M CONFIG > 28; 

my @ariginal_files = qw/ fred barney betty Wilma pebbles dino bam-bamm /; my @big_old_files; #要移到备份磁带上的文件 foreach my $filename (@original_files){ push @big_old_files, $filename if -s $filename > 100_100 and -A $filename > 90; } 

my ($dev, $ino, $mode, $nlink, $uid, $gid, $rdev, $size, $atime, $mtime, $ctime, $blksize, $blockes) = stat($filename); 

my($sec, $min, $hour, $day, $mon, $year, $wday, $yday, $isdst) = localtime $timestamp; 

my $timestamp = 1180630098; my $date = localtime $timestamp; 

my $now = gmtime; #得到当前的时间 

chdir "/etc" or die "cannot chdir to /etc: $!"; 

$ echo *.pm barney.pm dino.pm fred.pm wilma.pm $ 

$ cat > show_args foreach $arg (@ARGV) { print "one arg is $arg\n"; } ^D $ perl show_args * ... 

my @all_files = glob "*" ; my @pm_files = glob "*.pm"; 

my @all_files = <*>; # 基本上同 @all_files = glob "*" 一样 

my $dir = "/etc"; my @dir_files = <$dir/* $dir/.*>; 

my $dir_to_process = "/etc"; opendir 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; 

unlink "slate", "bedrock", "lava"; 

rename "over_there/some/place/some_file", "some_file"; 

my $where = readlink "carroll"; # 得到 "dodgson" my $perl = readlink "/usr/local/bin/perl" # 可能得到 Perl 放置的地方 

mkdir "fred", 0755 or warn "Cannot make fred directory: $!"; rmdir glob "fred/*"; # 删除 fred/下面所有的空目录 

chmod 0755, "fred", "barney"; 

my $user = 1004; my $group = 100; chown $user, $group, glob "*.o"; 

defined(my $user = getpwnam "merlyn") or die "user bad"; defined(my $group = getprnam "users") or die "group bad"; chown $user, $group, glob "/home/Merlyn/*"; 

my $now = time; my $ago = $now -24*60*60; # 一天的秒数 utime $now,$ago,glob "*" # 设成当前访问的,一天之前修改的 

$where = index($big, $small); 

$part = substr($string, $initial_position, $length); 

my $mineral = substr("Fred J. Flintstone", 8, 5); # 得到 "Flint" my $rock = substr "Fred J. Flintstone", 13, 1000; # 得到 "stone" my $pebble = substr "Fred J. Flintsone", 13; # 同上，得到 "stone" my $out = substr ("some very long string", -3, 2); # $out 得到 "in" 

#!/usr/bin/perl -w use strict; my $string = "Hello, world!"; substr($string,6) = "Jian Lee!"; print $string . "\n"; 

my $data_tag = sprintf "%4d/%02d/%02d %02d:%02d:%02d", $yr, $mo, $da, $h, $m, $s; 

system "date"; 

system 'ls -l $HOME'; 

system "ls -l \$HOME"; 

$ENV{'PATH'} = "/home/rootbeer/bin:$ENV('PATH')"; delete $ENV{'IFS'}; my $make_result = system "make"; 

my $now = `date`; # 捕获 date 的输出 print "The time is now $now"; # 已经有换行符 

open DATE, "date|" or die "Cannot pipe from date: $!"; open MAIL, "|mail merlyn" or die "Cannot pipe to mail: $!"; 

defined (my $pid= fork) or die "Cannot fork: $!"; unless ($pid){ #子进程在这里 exec "date"; die "cannot exec date: $!"; } #父进程在这里 waitpid($pid, 0); 

kill 2, 4201 or die "Cannot signal 4201 with SIGINT: $!"; 

$ perldoc CGI 

$ perl Makerfile.PL # $ perl Makerfile.PL PREFIX=/Users/fred/lib $ make install 

$ perl Build.PL $./Build install 

$ perl -MCPAN -e shell $ cpan Module::CoreList LWP CGI::Prototype 

use File::Basename; my $name = "/usr/local/bin/perl"; my $basename = basename $name; #得到 "perl" 

use File::Basename qw/ basename /; 

use File::Baename qw/ /; use File::Basename ( ); 

use File:Basename qw/ /; # 没有引入函数 my $betty = &dirname($wilma); # 使用我们自己的子程序 &dirname(这里没有显示) my $name = "/usr/local/bin/perl"; my $dirname = File::Basename::dirname $name; # 使用模块中的 dirname 

use File::Spec; #得到上面的$dirname, $basename 的值 my $new_name = File::Spec->catfile($dirname, $basename); rename($old_name, $new_name) or warn "Can't rename '$old_name' to '$new_name': $!"; 

eval { $barney = $fred / $dino }; # 即使除数为0也不会终止