Re^2: Reading binary file byte by byte

$/ is more flexible than you think.

{
   open(my $FILE, "file.binary") or die $!;
   binmode($FILE);

   local $/ = \1;
   while ( my $byte = <$FILE> ) {
      ...
   }

   close $FILE;
}
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But messing with global variables is messy. What if "..." calls a function that reads from a file? Just use read.

{
   open(my $FILE, "file.binary") or die $!;
   binmode($FILE);

   while (read($FILE, my $byte, 1)) {
      ...
   }

   close $FILE;
}
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Re^3: Reading binary file byte by byte by anonymized user 468275 (Curate) on Dec 23, 2010 at 13:26 UTC
Then we are back to reading a byte at a time from a file, which needs some thought applied first in terms of performance. It might be better than sysread which forces a system call with a 1 byte buffer, if thats what you request. Either way, if using buffered I/O, it seems more ept to read at least a page of memory in size at a time from the file but then process that one byte at a time. One world, one people	[reply]
Re^4: Reading binary file byte by byte by ikegami (Patriarch) on Dec 23, 2010 at 16:03 UTC
`read` and `readline` `(<>)` are buffered, so it's not that bad. If you need Perl-side buffering, the following would be much better: `use constant BLK_SIZE => 641024; { open(my $FILE, "file.binary") or die $!; binmode($FILE); while (read($FILE, my $buf, BLK_SIZE)) { for my $byte (unpack('a', $buf)) { ... } } close $FILE; }` [download]	[reply] [d/l] [select]