Programming Perl, 3rd Edition

FileHandle

use FileHandle;

$fh = new FileHandle;
if ($fh->open("< file")) {
    print $line while defined($line = $fh->getline);
    $fh->close;
}

$pos = $fh->getpos;     # like tell()
$fh->setpos($pos);      # like seek()

($readfh, $writefh) = FileHandle::pipe();

autoflush STDOUT 1;

The FileHandle module mostly serves as a mechanism for cloaking Perl's punctuation variables in longer, more OO-looking calls. It is provided for compatibility with older releases, but is now really only a frontend for several more specific modules, like IO::Handle and IO::File.^[5] Its best property is the low-level access it provides to certain rare functions from the C library (clearerr (3), fgetpos (3), fsetpos (3), and setvbuf (3)).

Variable	Method
$|	autoflush
$,	output_field_separator
$\	output_record_separator
$/	input_record_separator
$.	input_line_number
$%	format_page_number
$=	format_lines_per_page
$-	format_lines_left
$~	format_name
$^	format_top_name
$:	format_line_break_characters
$^L	format_formfeed

Instead of saying:

$ofh = select(HANDLE);
$~ = 'SomeFormat';
$| = 1;
select($ofh);

you can just say:

use FileHandle;
HANDLE->format_name('SomeFormat');
HANDLE->autoflush(1);

Currently, three methods (output_field_separator, output_record_separator, and input_record_separator) only pretend to be per-handle methods: setting them on one handle actually affects all filehandles. They are therefore only supported as class methods, not as per-filehandle methods. This restriction may be lifted someday.

To get a lexically scoped filehandle, instead ...