filehandle(3)
NAME
FileHandle - supply object methods for filehandles
SYNOPSIS
use FileHandle;
$fh = new FileHandle;
if ($fh->open("< file")) {
print <$fh>;
$fh->close;
}
$fh = new FileHandle "> FOO";
if (defined $fh) {
print $fh "bar0;
$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 "corge0;
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;
DESCRIPTION
NOTE: This class is now a front-end to the IO::* classes.
"FileHandle::new" creates a "FileHandle", which is a ref
erence to a newly created symbol (see the "Symbol" pack
age). 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 "File
Handle" 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
characters, and the second parameter is the open mode,
optionally 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 "FileHan
dle::setvbuf" sets the buffering policy for the FileHan
dle. 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: - close
fileno
getc
gets
eof
clearerr
seek
tell - See perlvar for complete descriptions of each of the fol
lowing 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 acciden tally 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.
SEE ALSO
- The IO extension, perlfunc, "I/O Operators" in perlop.