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GNU/Linux |
CentOS 2.1AS(Slurm) |
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Symbol(3pm) |
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Symbol − manipulate Perl symbols and their names
use Symbol;
$sym = gensym;
open($sym, "filename");
$_ = <$sym>;
# etc.
ungensym $sym; # no effect
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::’};
"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::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.
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Symbol(3pm) | |