NAME

IO::Handle - supply object methods for I/O handles

SYNOPSIS

    use IO::Handle;

    $fh = new IO::Handle;
    if ($fh->open "< file") {
        print <$fh>;
        $fh->close;
    }

    $fh = new IO::Handle "> FOO";
    if (defined $fh) {
        print $fh "bar\n";
        $fh->close;
    }

    $fh = new IO::Handle "file", "r";
    if (defined $fh) {
        print <$fh>;
        undef $fh;       # automatically closes the file
    }

    $fh = new IO::Handle "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);

    autoflush STDOUT 1;

DESCRIPTION

IO::Handle is the base class for all other IO handle classes. A IO::Handle object is a reference to a symbol (see the Symbol package)

CONSTRUCTOR

new ()

Creates a new IO::Handle object.

new_from_fd ( FD, MODE )

Creates a IO::Handle like new does. It requires two parameters, which are passed to the method fdopen; if the fdopen fails, the object is destroyed. Otherwise, it is returned to the caller.

METHODS

If the C function setvbuf() is available, then IO::Handle::setvbuf sets the buffering policy for the IO::Handle. 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 IO::Handle::setvbuf must not be modified in any way until the IO::Handle is closed or until IO::Handle::setvbuf is called again, or memory corruption may result!

See perlfunc for complete descriptions of each of the following supported IO::Handle methods, which are just front ends for the corresponding built-in functions:

    close
    fileno
    getc
    gets
    eof
    read
    truncate
    stat
    print
    printf
    sysread
    syswrite

See perlvar for complete descriptions of each of the following supported IO::Handle 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
    format_write

Furthermore, for doing normal I/O you might need these:

$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 an array context but still returns just one line.

$fh->getlines

This works like <$fh> when called in an array 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.

$fh->fdopen ( FD, MODE )

fdopen is like an ordinary open except that its first parameter is not a filename but rather a file handle name, a IO::Handle object, or a file descriptor number.

$fh->write ( BUF, LEN [, OFFSET }\] )

write is like write found in C, that is it is the opposite of read. The wrapper for the perl write function is called format_write.

$fh->opened

Returns true if the object is currently a valid file descriptor.

Lastly, a special method for working under -T and setuid/gid scripts:

$fh->untaint

Marks the object as taint-clean, and as such data read from it will also be considered taint-clean. Note that this is a very trusting action to take, and appropriate consideration for the data source and potential vulnerability should be kept in mind.

NOTE

A IO::Handle object is a GLOB reference. Some modules that inherit from IO::Handle may want to keep object related variables in the hash table part of the GLOB. In an attempt to prevent modules trampling on each other I propose the that any such module should prefix its variables with its own name separated by _'s. For example the IO::Socket module keeps a timeout variable in 'io_socket_timeout'.

SEE ALSO

perlfunc, "I/O Operators" in perlop, "FileHandle" in POSIX

BUGS

Due to backwards compatibility, all filehandles resemble objects of class IO::Handle, or actually classes derived from that class. They actually aren't. Which means you can't derive your own class from IO::Handle and inherit those methods.

HISTORY

Derived from FileHandle.pm by Graham Barr <bodg@tiuk.ti.com>