FileHandle(3pm) Perl Programmers Reference Guide FileHandle(3pm)
NAME
FileHandle - supply object methods for filehandles
SYNOPSIS
use FileHandle;
my $fh = FileHandle->new;
if ($fh->open("< file")) {
print <$fh>;
$fh->close;
}
my $fh = FileHandle->new("> FOO");
if (defined $fh) {
print $fh "bar\n";
$fh->close;
}
my $fh = FileHandle->new("file", "r");
if (defined $fh) {
print <$fh>;
undef $fh; # automatically closes the file
}
my $fh = FileHandle->new("file", O_WRONLY|O_APPEND);
if (defined $fh) {
print $fh "corge\n";
undef $fh; # automatically closes the file
}
my $pos = $fh->getpos;
$fh->setpos($pos);
$fh->setvbuf(my $buffer_var, _IOLBF, 1024);
my ($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
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 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
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 following
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 following
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.
SEE ALSO
The IO(3) extension, perlfunc(1), "I/O Operators" in perlop(1).
perl v5.38.2 2023-11-28 FileHandle(3pm)
perl 5.38.2 - Generated Fri Dec 6 12:53:22 CST 2024