perl学习笔记-5

#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/#.* //;
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. ";
} else {
print "The value of $freed doesn't look like a Perl identifier name. ";
}
#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. ";
} else {
print "The value of $freed really look like a Perl identifier name. ";
}

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. " 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. ";
}

#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 ";
printf "Second: $s ";
printf "Third: $t ";
$x = join ":","$f","$s","$t"; #再连接起来
print "$x ";

#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! "; #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. ";
}

#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,$_! "
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 ";
#}

#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 ";
}

#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 ";
}
closedir DH;