FileHandle(3) Perl Programmers Reference Guide FileHandle(3)NAMEFileHandle - 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 "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;
DESCRIPTION
NOTE: This class is now a front-end to the IO::* classes.
"FileHandle::new" creates a "FileHandle", which is a reference 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" 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 white‐
space 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 "File‐
Handle::getpos" returns an opaque value that represents the current
position of the FileHandle, and "FileHandle::setpos" uses that value to
return to a previously 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 parame‐
ter specifies a scalar variable to use as a buffer. WARNING: A vari‐
able 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 following sup‐
ported "FileHandle" methods, which are just front ends for the corre‐
sponding built-in functions:
close
fileno
getc
gets
eof
clearerr
seek
tell
See perlvar for complete descriptions of each of the following sup‐
ported "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 respec‐
tive pages for documentation on more functions.
SEE ALSO
The IO extension, perlfunc, "I/O Operators" in perlop.
perl v5.8.8 2008-09-19 FileHandle(3)