# phpman > perldoc > IO::InnerFile

## NAME
    [IO::InnerFile](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AInnerFile/markdown) - define a file inside another file

## SYNOPSIS
        ### Read a subset of a file:
        $inner = [IO::InnerFile](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AInnerFile/markdown)->new($fh, $start, $length);
        while (<$inner>) {
            ...
        }

## DESCRIPTION
    If you have a filehandle that can seek() and tell(), then you can open an [IO::InnerFile](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AInnerFile/markdown) on a
    range of the underlying file.

## PUBLIC INTERFACE
    new FILEHANDLE, [START, [LENGTH]]
        *Class method, constructor.* Create a new inner-file opened on the given FILEHANDLE, from
        bytes START to START+LENGTH. Both START and LENGTH default to 0; negative values are
        silently coerced to zero.

        Note that FILEHANDLE must be able to seek() and tell(), in addition to whatever other
        methods you may desire for reading it.

    set_length LENGTH
    get_length
    add_length NBYTES
        *Instance methods.* Get/set the virtual length of the inner file.

    set_start START
    get_start
    add_start NBYTES
        *Instance methods.* Get/set the virtual start position of the inner file.

    binmode
    close
    flush
    getc
    getline
    print LIST
    printf LIST
    read BUF, NBYTES
    readline
    seek OFFFSET, WHENCE
    tell
    write ARGS...
        *Instance methods.* Standard filehandle methods.

## VERSION
    $Id: InnerFile.pm,v 1.4 2005/02/10 21:21:53 dfs Exp $

## AUTHOR
    Original version by Doru Petrescu (<pdoru@kappa.ro>).

    Documentation and by Eryq (<eryq@zeegee.com>).

    Currently maintained by Dianne Skoll (<dfs@roaringpenguin.com>).