Perl 学习手札之十二：Files IO

understanding blocks and streams

there are two ways to look at files

 -blocks of data

 -stream

a block of data simply a chunk of the file that can be written or read in one operation.

a stream is data that may come as a series of bytes

 - keystrokes from a user

 - data sent over a network connection

handles.pl

#!/usr/bin/perl
#
use strict;
use warnings;

main(@ARGV);

sub main
{
    open(FH, '<', 'workingfile.txt') or error("cannot open file for read($!)");
    #print while <FH>;
    open(NFH, '>', 'newfile.txt') or error("cannot open file for write($!)");  
    
    print NFH while <FH>;
      
    close FH;
    close NFH;
}

sub message
{
    my $m = shift or return;
    print("$m\n");
}

sub error
{
    my $e = shift || 'unkown error';
    print(STDERR "$0: $e\n");
    exit 0;
}

oofiles.pl

#!/usr/bin/perl
#
use strict;
use warnings;
use IO::File;

main(@ARGV);

sub main
{
    my $fh = IO::File->new('workingfile.txt','r') or error("can not open file for read($!)");
    my $nfh = IO::File->new('newfile.txt','w') or error("can not open file for write($!)");
    #print while <$fh>;
    while(my $line = $fh->getline){
        $nfh->print($line);
    }

}

sub message
{
    my $m = shift or return;
    print("$m\n");
}

sub error
{
    my $e = shift || 'unkown error';
    print(STDERR "$0: $e\n");
    exit 0;
}

 应用面向对象的方法操作。可以

binary.pl

#!/usr/bin/perl
#
use strict;
use warnings;
use IO::File;

main(@ARGV);

sub main
{
    my $origfile = "olives.jpg";
    my $newfile = "copy.jpg";
    my $bufsize = 1024*1024;
    
    my $origfh = IO::File->new($origfile,'r')
        or error("cannot open $origfile($!)");
    my $newfh = IO::File->new($newfile,'w')
        or error("cannot open $newfile($!)");
        
    $origfh->binmode(":raw");
    $newfh->binmode(":raw");
    
    my $buf = '';
    while($origfh->read($buf,$bufsize)){
        $newfh->print($buf);
    }
    message("done");
}

sub message
{
    my $m = shift or return;
    print("$m\n");
}

sub error
{
    my $e = shift || 'unkown error';
    print(STDERR "$0: $e\n");
    exit 0;
}

 注意：用到的binary mode。我们是用面向对象的方法打开文件，读到buffer里面，然后print输出到文件。