manpagez: man pages & more
man Symbol(3)
Home | html | info | man
Symbol(3pm)            Perl Programmers Reference Guide            Symbol(3pm)




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";              # "main::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
       support 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
       variable names (e.g. "myvar" -> "MyPackage::myvar").  If it is given a
       second 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
       symbol that lives in the specified package. 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 v5.26.1                      2017-07-18                       Symbol(3pm)

perl 5.26.1 - Generated Mon Nov 6 18:36:49 CST 2017
© manpagez.com 2000-2017
Individual documents may contain additional copyright information.