Perl 学习手札之十二：Files IO
understanding blocks and streamsthere 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。
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