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# tie

Perl 5 version 10.1 documentation
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# tie

Perl functions A-Z | Perl functions by category | The 'perlfunc' manpage

- tie VARIABLE,CLASSNAME,LIST

  This function binds a variable to a package class that will provide the implementation for the variable. VARIABLE is the name of the variable to be enchanted. CLASSNAME is the name of a class implementing objects of correct type. Any additional arguments are passed to the `new` method of the class (meaning `TIESCALAR` , `TIEHANDLE` , `TIEARRAY` , or `TIEHASH` ). Typically these are arguments such as might be passed to the `dbm_open()` function of C. The object returned by the `new` method is also returned by the `tie` function, which would be useful if you want to access other methods in CLASSNAME.

  Note that functions such as `keys` and `values` may return huge lists when used on large objects, like DBM files. You may prefer to use the `each` function to iterate over such. Example:

          # print out history file offsets    use NDBM_File;    tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);    while (($key,$val) = each %HIST) {	print $key, ' = ', unpack('L',$val), "\n";    }    untie(%HIST);

  A class implementing a hash should have the following methods:

          TIEHASH classname, LIST    FETCH this, key    STORE this, key, value    DELETE this, key    CLEAR this    EXISTS this, key    FIRSTKEY this    NEXTKEY this, lastkey    SCALAR this    DESTROY this    UNTIE this

  A class implementing an ordinary array should have the following methods:

          TIEARRAY classname, LIST    FETCH this, key    STORE this, key, value    FETCHSIZE this    STORESIZE this, count    CLEAR this    PUSH this, LIST    POP this    SHIFT this    UNSHIFT this, LIST    SPLICE this, offset, length, LIST    EXTEND this, count    DESTROY this    UNTIE this

  A class implementing a file handle should have the following methods:

          TIEHANDLE classname, LIST    READ this, scalar, length, offset    READLINE this    GETC this    WRITE this, scalar, length, offset    PRINT this, LIST    PRINTF this, format, LIST    BINMODE this    EOF this    FILENO this    SEEK this, position, whence    TELL this    OPEN this, mode, LIST    CLOSE this    DESTROY this    UNTIE this

  A class implementing a scalar should have the following methods:

          TIESCALAR classname, LIST    FETCH this,    STORE this, value    DESTROY this    UNTIE this

  Not all methods indicated above need be implemented. See perltie, Tie::Hash, Tie::Array, Tie::Scalar, and Tie::Handle.

  Unlike `dbmopen`, the `tie` function will not use or require a module for you--you need to do that explicitly yourself. See DB_File or the Config module for interesting `tie` implementations.

  For further details see perltie, "tied VARIABLE".

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