perl学习笔记(五)

#!/usr/bin/perl

use 5.010;

say "-----------FreezeThaw模块------------------------";
#将复杂结构编码成可以打印的ASCII字符串，使用者可以将编码后的字符串发送到文件、DBM文件、数据库。
#use FreezeThaw qw(freeze thaw);#加载freeze()和thaw()
=pod
$c = {
	'even' => [2,4,6,8],
	'odd'  => [1,3,5,7]
};
$obj = bless ('foo' => 'bar'), 'Example';
$msg = freeze($c,$obj);#数组和散列表必须用引用的形式传递
open(F,'>freeze')||die;
syswtite(F,$msg,length($msg));
($c,$obj) = thaw($msg);#thaw方法读取一个编码过的字符串并返回同样的标量变量列表
=cut

say "-----------Data::Dumper模块------------------------";
#转换成格式美观的perl代码，可以存储到文件中，以后可以进行eval操作
use Data::Dumper;
$c = {
	even => [2,4,6,8,],
	old => [1,3,5,7,]
};
#创建样例对象
$obj = bless {'foo' => 'bar'},'Example';
#$obj = bless $c,'Example';
$msg = Dumper($c,$obj);
#say $msg;
$n = eval($msg);
say $n->{'foo'};
#say $n->{'even'}[0];

say "-----------Storable模块------------------------";
use Storable;
$a = [100,200,{"name" => 'giggs'}];
eval{
	store($a,'test.dat');#指向数据结构(根)的引用，文件名
};
say "error writing to file :$@" if $@;

$a = retrieve('test.dat');#完成相反的工作，给定文件名，返回数据结构的引用
say $a->[0];
say $a->[2]->{"name"};

say "-----------DBI模块--交互式sql前端----------------------";
#错误代码和错误信息$DBI::err和$DBI::errstr
use DBI;
$dbname = 'zhbd';
$user = 'zhbd';
$password = 'zhbd!@#';
$dbd = 'Pg';
my $db = "DBI:Pg:database=zhbd";
$dbh = DBI->connect($db,$user,$password) || 
die "Errot connecting $DBI::errstr";

while(1){
	print "SQL> ";
	$command = <STDIN>;
	last unless defined($command);
	last if ($command =~ /^\s*exit/);
	chomp($command);
	$command =~ s/;\s*$//;
	$sth = $dbh->prepare($command);
	if ($DBI::err) {
		say STDERR "$DBI:errstr";
		next;
	}
	$sth->execute();
	if ($DBI::err) {
		say STDERR "$DBI:errstr";
		next;
	}
	if($command =~ /^\s*select/i){
		my $rl_names =$sth->{NAME}; #列名数组的引用
		say "-----";
		while(@results = $sth->fetchrow){	#检索结果
			say "@results";
			say "***********************";
			if ($DBI::err) {
				say STDERR "$DBI:errstr";
				last;
			}
			foreach $field_name (@$rl_names) {
				printf "%10s: %s\n",$field_name,shift @results;
				print "\n";
			}
		}
		$sth->finish;
	}
}
$dbh->commit;