Does _LAST_ and &SYSLAST always means the same value?

[whymath]

I am going to write some macro and want to know which one is more robuster.

[Kurt_Bremser]

According to the documentation, they will deliver the same value. With %SYSLAST, take care of macro timing rules and the trailing blanks.

[Quentin]

Generally I'm not a fan of _LAST_ or &SYSLAST, and I think it was a bad language design decision to have a PROC step default to reading _LAST_ if no dataset is specified.

It's part of the language so it's not going to change, but I would avoid relying on either.

That said, I think they really might be the same thing.  I just noticed that if you assign a value the the macro variable SYSLAST, the value will be used by _LAST_, e.g.:

%let syslast=sashelp.class ;

proc print data=_last_(obs=3) ;
run ;

%let syslast=sashelp.shoes ;

proc print data=_last_(obs=3) ;
run ;

options _last_=sashelp.prdsale ;
%put &syslast ;

proc print ;
run ;

[Tom · Accepted solution]

They will both reference the same dataset, if that is what you meant.

But they aren't the same thing at all.

_LAST_ is a keyword you can use in places where SAS syntax expects a dataset name.

SYSLAST is a macro variable.  You can use it anywhere you would use a macro variable.