Determines if current environment is eligible for update suggestion.
@@foo += bar ^^^^^^^^^^^^
@@foo &&= bar ^^^^^^^^^^^^^
@@foo ||= bar ^^^^^^^^^^^^^
$foo += bar ^^^^^^^^^^^
$foo &&= bar ^^^^^^^^^^^^
$foo ||= bar ^^^^^^^^^^^^
foo += bar ^^^^^^^^^^
foo &&= bar ^^^^^^^^^^^
foo ||= bar ^^^^^^^^^^^
@@foo += bar ^^^^^^^^^^^^
@@foo &&= bar ^^^^^^^^^^^^^
@@foo ||= bar ^^^^^^^^^^^^^
$foo += bar ^^^^^^^^^^^
$foo &&= bar ^^^^^^^^^^^^
$foo ||= bar ^^^^^^^^^^^^
foo += bar ^^^^^^^^^^
foo &&= bar ^^^^^^^^^^^
foo ||= bar ^^^^^^^^^^^
Open the specified filename (either in read-only mode or in read-write mode) and lock it for reading or writing.
The opened File
object will be returned. If read_only is true, and the file does not exist, then nil will be returned.
All exceptions are propagated.