Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
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";		  # "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 v5.26.0			  2017-04-19			     Symbol(3)

NAME | SYNOPSIS | DESCRIPTION | BUGS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=Symbol&sektion=3&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help