学习笔记-Perl-记录最简单的一些实例-3

#Example21        #对文件的处理
#!/usr/bin/perl -w          
#Usage:perl test1.pl test?.txt      #用"?"不用"*"可以加快程序运行

use strict;

chomp(my $date = `date`);   #引用系统命令date，取当前系统日期，保存到"$date"中
$^I = ".bak";               #程序自动生成备份文件，并将".bak"追加到名字后面去

while (<>){                 #读入txt文件
  s/^print/printf/;
  s/\#.*\n//;
  print;
}

#perl -p -i.bak -w -e 's/print/printf/g' test*.pl.bak
#这是一条命令
#-p自动生成一小段程序 -i.bak 制定后缀名(如果不需要备份，只写-i即可) -w打开警告信息 -e后面跟着的是程序代码
#将test*.pl.bak文件中所有的print改成printf，并生成源文件的备份，将.bak追加到备份文件后面
#于是，我们得到的文件时test*.pl.bak和test*.pl.bak.bak

#-----------------------------------------------------------------------------------------------------------------------------------------------------
#Example21        #Perl程序控制
#!/usr/bin/perl -w  
if ($freed =~ /^[A-Z_]\w*$/i){
print "The value of \$freed really look like a Perl identifier name.\n";
} else {
print "The value of \$freed doesn't look like a Perl identifier name.\n";
}
#以上程序与下面的功能完全一样

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

while($j < $i){
$j*=2;
}
#以上程序与下面的功能完全一样

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

print "The value of \$freed really look like a Perl identifier name.\n" if $freed =~ /^[A-Z_]\w*$/i ;
#以上程序与下面的功能完全一样

if ($freed =~ /^[A-Z_]\w*$/i){
print "The value of \$freed really look like a Perl identifier name.\n";
}

#开开眼界吧，这都什么东西啊，但是他们确实可以执行
&error("Invalid input") unless &valid($input);   
$i *= 2 until $i > $j;
print " ", ($n +=2) while $n < 10;
&greet($_) foreach @person;

#-----------------------------------------------------------------------------------------------------------------------------------------------------
#Example22        #定义多个变量
#!/usr/bin/perl

$_ = "Hello there, neigthor!";          #一下子定义三个变量
my($f, $s, $t) = /(\S+) (\S+), (\S+)/;
printf "First: $f\n";
printf "Second: $s\n";
printf "Third: $t\n";
$x = join "\:","$f","$s","$t";          #再连接起来
print "$x\n";

#-----------------------------------------------------------------------------------------------------------------------------------------------------
#Example23        #读入文件，并做统计
#!/usr/bin/perl

while (<>) {      #转世操作符，分行读入
 foreach (split) {   #用空格拆分
  $total++;
  next if /\W/;      #如果该字符串含有特殊字符，跳过下面的
  $valid++;          #不含特殊字符的正常的单词
  $count{$_}++;      #统计每个单词个数
  }
}

print "Total things = $total, Valid words = $valid!\n";  #输出统计信息
foreach $word (sort keys %count) {    #这个很好玩，再猜几次吧
print "$word was seen $count{$word} times.\n";
}

#-----------------------------------------------------------------------------------------------------------------------------------------------------
#Example24        #统计字符串是否曾经出现过
#!/usr/bin/perl -w
my @people = qw{ Fred abc Fred bam bam nm bc nu ;lll};
my %seen;
for (@people) {
 print "I've seen you somewhere before,$_!\n" 
 if $seen{$_}++;
}

#-----------------------------------------------------------------------------------------------------------------------------------------------------
#Example25        #获取某类文件，并存入@ARGV中
#!/usr/bin/perl -w
#第一段的执行方式是: perl test5.pl *.pl
#第二段的执行方式是: perl test5.pl

#foreach $arg (@ARGV) {
# print "One arg is $arg\n";
#}

#my @ARGV = glob "*.pl";
#my @ARGV = <*>;
my $dir = "/bocnet/app_bak/yu/yu_perl";
my @ARGV = <$dir/* $dir/.*>; 
foreach $arg (@ARGV) {
 print "One arg is $arg\n";
}

#-----------------------------------------------------------------------------------------------------------------------------------------------------
#Example26         #目录句柄
#!/usr/bin/perl -w

my $dir = "/bocnet/app_bak/yu/yu_perl";
opendir DH,$dir or die "Cannot open $dir: $!";
foreach $file (readdir DH) {
  print "One file in $dir if $file\n";
}
closedir DH;