gsub variables

[Steve V]

Are the $1, $`, $&, etc... variables within a gsub block truely global, or
are they some type of special value local to the block? To be global would
be fine in a single user environment, but in a multi-user web environment it
seems like this could cause problems. Do I need to worry about multi-user
issues with gsub?

Thanks,
Steve

 

[Glenn Parker]

Are the $1, $`, $&, etc... variables within a gsub block truely global, or
are they some type of special value local to the block?

They are actually per-thread variables, meaning they look like global
variables, but each thread maintains its own separate set of values for
them.

To be global would
be fine in a single user environment, but in a multi-user web environment it
seems like this could cause problems. Do I need to worry about multi-user
issues with gsub?

It depends on how you invoke Ruby. The only way I can see it being a
problem is if the state from the last Regexp operation during one
transaction were to leak into the next transaction. In other words, if
the very first thing a web transaction did was:

last_match = $&

Then maybe it could steal some information from an earlier transaction,
assuming that a long-lived thread handled multiple transactions. But if
every transaction is handled in a new thread, or in a new Ruby process,
then $& will always be nil to start with.

 

[Tim Hunter]

Are the $1, $`, $&, etc... variables within a gsub block truely global, or
are they some type of special value local to the block? To be global would
be fine in a single user environment, but in a multi-user web environment it
seems like this could cause problems. Do I need to worry about multi-user
issues with gsub?

Thanks,
Steve

According to the Pickaxe II, they're all local to the thread.

 

[Steve V]

Are the $1, $`, $&, etc... variables within a gsub block truely

global, or

They are actually per-thread variables, meaning they look like global
variables, but each thread maintains its own separate set of values for
them.

Thanks everyone for the quick response.

Steve