Symbol

Symbol(3)              Perl Programmers Reference Guide              Symbol(3)



NAME
       Symbol - manipulate Perl symbols and their names

SYNOPSIS
           use Symbol;

           $sym = gensym;
           open($sym, "filename");
           $_ = <$sym>;
           # etc.

           ungensym $sym;      # no effect

           # replace *FOO{IO} handle but not $FOO, %FOO, etc.
           *FOO = geniosym;

           print qualify("x"), "\n";              # "Test::x"
           print qualify("x", "FOO"), "\n"        # "FOO::x"
           print qualify("BAR::x"), "\n";         # "BAR::x"
           print qualify("BAR::x", "FOO"), "\n";  # "BAR::x"
           print qualify("STDOUT", "FOO"), "\n";  # "main::STDOUT" (global)
           print qualify(\*x), "\n";              # returns \*x
           print qualify(\*x, "FOO"), "\n";       # returns \*x

           use strict refs;
           print { qualify_to_ref $fh } "foo!\n";
           $ref = qualify_to_ref $name, $pkg;

           use Symbol qw(delete_package);
           delete_package('Foo::Bar');
           print "deleted\n" unless exists $Foo::{'Bar::'};

DESCRIPTION
       "Symbol::gensym" creates an anonymous glob and returns a reference to
       it.  Such a glob reference can be used as a file or directory handle.

       For backward compatibility with older implementations that didn't sup-
       port anonymous globs, "Symbol::ungensym" is also provided.  But it
       doesn't do anything.

       "Symbol::geniosym" creates an anonymous IO handle.  This can be
       assigned into an existing glob without affecting the non-IO portions of
       the glob.

       "Symbol::qualify" turns unqualified symbol names into qualified vari-
       able names (e.g. "myvar" -> "MyPackage::myvar").  If it is given a sec-
       ond parameter, "qualify" uses it as the default package; otherwise, it
       uses the package of its caller.  Regardless, global variable names
       (e.g. "STDOUT", "ENV", "SIG") are always qualified with "main::".

       Qualification applies only to symbol names (strings).  References are
       left unchanged under the assumption that they are glob references,
       which are qualified by their nature.

       "Symbol::qualify_to_ref" is just like "Symbol::qualify" except that it
       returns a glob ref rather than a symbol name, so you can use the result
       even if "use strict 'refs'" is in effect.

       "Symbol::delete_package" wipes out a whole package namespace.  Note
       this routine is not exported by default--you may want to import it
       explicitly.

BUGS
       "Symbol::delete_package" is a bit too powerful. It undefines every sym-
       bol that lives in the specified package and in its sub-packages. Since
       perl, for performance reasons, does not perform a symbol table lookup
       each time a function is called or a global variable is accessed, some
       code that has already been loaded and that makes use of symbols in
       package "Foo" may stop working after you delete "Foo", even if you
       reload the "Foo" module afterwards.



perl v5.8.6                       2001-09-21                         Symbol(3)