Tie::Handle

Section: Perl Programmers Reference Guide (3pm)
Updated: 2021-03-31
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NAME

Tie::Handle - base class definitions for tied handles

SYNOPSIS

    package NewHandle;
    require Tie::Handle;

    @ISA = qw(Tie::Handle);

    sub READ { ... }            # Provide a needed method
    sub TIEHANDLE { ... }       # Overrides inherited method


    package main;

    tie *FH, 'NewHandle';

DESCRIPTION

This module provides some skeletal methods for handle-tying classes. See perltie for a list of the functions required in tying a handle to a package. The basic Tie::Handle package provides a "new" method, as well as methods "TIEHANDLE", "PRINT", "PRINTF" and "GETC".

For developers wishing to write their own tied-handle classes, the methods are summarized below. The perltie section not only documents these, but has sample code as well:

TIEHANDLE classname, LIST: The method invoked by the command "tie *glob, classname". Associates a new glob instance with the specified class. "LIST" would represent additional arguments (along the lines of AnyDBM_File and compatriots) needed to complete the association.
WRITE this, scalar, length, offset: Write length bytes of data from scalar starting at offset.
PRINT this, LIST: Print the values in LIST
PRINTF this, format, LIST: Print the values in LIST using format
READ this, scalar, length, offset: Read length bytes of data into scalar starting at offset.
READLINE this: Read a single line
GETC this: Get a single character
CLOSE this: Close the handle
OPEN this, filename: (Re-)open the handle
BINMODE this: Specify content is binary
EOF this: Test for end of file.
TELL this: Return position in the file.
SEEK this, offset, whence: Position the file.
Test for end of file.
DESTROY this: Free the storage associated with the tied handle referenced by this. This is rarely needed, as Perl manages its memory quite well. But the option exists, should a class wish to perform specific actions upon the destruction of an instance.

MORE INFORMATION

The perltie section contains an example of tying handles.

COMPATIBILITY

This version of Tie::Handle is neither related to nor compatible with the Tie::Handle (3.0) module available on CPAN. It was due to an accident that two modules with the same name appeared. The namespace clash has been cleared in favor of this module that comes with the perl core in September 2000 and accordingly the version number has been bumped up to 4.0.