FileHandle(3p) Perl Programmers Reference Guide FileHandle(3p)
FileHandle - supply object methods for filehandles
use FileHandle;
$fh = new FileHandle;
if ($fh->open("< file")) {
print <$fh>;
$fh->close;
}
$fh = new FileHandle "> FOO";
if (defined $fh) {
print $fh "bar\n";
$fh->close;
}
$fh = new FileHandle "file", "r";
if (defined $fh) {
print <$fh>;
undef $fh; # automatically closes the file
}
$fh = new FileHandle "file", O_WRONLY|O_APPEND;
if (defined $fh) {
print $fh "corge\n";
undef $fh; # automatically closes the file
}
$pos = $fh->getpos;
$fh->setpos($pos);
$fh->setvbuf($buffer_var, _IOLBF, 1024);
($readfh, $writefh) = FileHandle::pipe;
autoflush STDOUT 1;
NOTE: This class is now a front-end to the IO::* classes.
"FileHandle::new" creates a "FileHandle", which is a refer-
ence to a newly created symbol (see the "Symbol" package).
If it receives any parameters, they are passed to
"FileHandle::open"; if the open fails, the "FileHandle"
object is destroyed. Otherwise, it is returned to the
caller.
"FileHandle::new_from_fd" creates a "FileHandle" like "new"
does. It requires two parameters, which are passed to
"FileHandle::fdopen"; if the fdopen fails, the "FileHandle"
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FileHandle(3p) Perl Programmers Reference Guide FileHandle(3p)
object is destroyed. Otherwise, it is returned to the
caller.
"FileHandle::open" accepts one parameter or two. With one
parameter, it is just a front end for the built-in "open"
function. With two parameters, the first parameter is a
filename that may include whitespace or other special char-
acters, and the second parameter is the open mode, option-
ally followed by a file permission value.
If "FileHandle::open" receives a Perl mode string (">",
"+<", etc.) or a POSIX fopen() mode string ("w", "r+",
etc.), it uses the basic Perl "open" operator.
If "FileHandle::open" is given a numeric mode, it passes
that mode and the optional permissions value to the Perl
"sysopen" operator. For convenience, "FileHandle::import"
tries to import the O_XXX constants from the Fcntl module.
If dynamic loading is not available, this may fail, but the
rest of FileHandle will still work.
"FileHandle::fdopen" is like "open" except that its first
parameter is not a filename but rather a file handle name, a
FileHandle object, or a file descriptor number.
If the C functions fgetpos() and fsetpos() are available,
then "FileHandle::getpos" returns an opaque value that
represents the current position of the FileHandle, and
"FileHandle::setpos" uses that value to return to a previ-
ously visited position.
If the C function setvbuf() is available, then
"FileHandle::setvbuf" sets the buffering policy for the
FileHandle. The calling sequence for the Perl function is
the same as its C counterpart, including the macros
"_IOFBF", "_IOLBF", and "_IONBF", except that the buffer
parameter specifies a scalar variable to use as a buffer.
WARNING: A variable used as a buffer by
"FileHandle::setvbuf" must not be modified in any way until
the FileHandle is closed or until "FileHandle::setvbuf" is
called again, or memory corruption may result!
See perlfunc for complete descriptions of each of the fol-
lowing supported "FileHandle" methods, which are just front
ends for the corresponding built-in functions:
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FileHandle(3p) Perl Programmers Reference Guide FileHandle(3p)
close
fileno
getc
gets
eof
clearerr
seek
tell
See perlvar for complete descriptions of each of the follow-
ing supported "FileHandle" methods:
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
format_formfeed
Furthermore, for doing normal I/O you might need these:
$fh->print
See "print" in perlfunc.
$fh->printf
See "printf" in perlfunc.
$fh->getline
This works like <$fh> described in "I/O Operators" in
perlop except that it's more readable and can be safely
called in a list context but still returns just one
line.
$fh->getlines
This works like <$fh> when called in a list context to
read all the remaining lines in a file, except that it's
more readable. It will also croak() if accidentally
called in a scalar context.
There are many other functions available since FileHandle is
descended from IO::File, IO::Seekable, and IO::Handle.
Please see those respective pages for documentation on more
functions.
The IO extension, perlfunc, "I/O Operators" in perlop.
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