gsub!(pattern, replacement)    → string or nil
gsub!(pattern) {|...| block }  → string or nil

Equivalent to Kernel::gsub, except nil is returned if $_ is not modified.

$_ = "quick brown fox"
gsub! /cat/, '*'   #=> nil
$_                 #=> "quick brown fox"

Source Code

/*
*  call-seq:
*     gsub!(pattern, replacement)    => string or nil
*     gsub!(pattern) {|...| block }  => string or nil
*  
*  Equivalent to <code>Kernel::gsub</code>, except <code>nil</code> is
*  returned if <code>$_</code> is not modified.
*     
*     $_ = "quick brown fox"
*     gsub! /cat/, '*'   #=> nil
*     $_                 #=> "quick brown fox"
*/

static VALUE
rb_f_gsub_bang(argc, argv)
   int argc;
   VALUE *argv;
{
   return rb_str_gsub_bang(argc, argv, uscore_get());
}