On Fri, 2013-04-26 at 16:42 +0300, Cristian Sava wrote: > On Fri, 2013-04-26 at 08:30 -0500, Chris Adams wrote: > > Once upon a time, Jonathan Kamens <jik@xxxxxxxxx> said: > > > This, however, is fine: > > > > > > [ "$WEBALIZER_CRON" != yes ] > > > > > > because the quotes ensure that the statement will be evaluated with an > > > expression to the left of the != even if the expression is just an empty > > > string. > > > > > > This is fine too: > > > > > > [ z$WEBALIZER_CRON != zyes ] > > > > > > because if the variable is empty, the expression to the left will be "z" > > > rather than an empty string. > > > > The reason some use a combination of quotes and a leading character is > > for testing user-provided input. It shouldn't matter in this case, but > > it is just a little bit more defensive programming. > > > > The problem if you are testing a user-provided variable is that they > > could give input that starts with a dash, a close bracket, etc., and > > that would screw up the test. Putting a character at the start protects > > against that. > > > > Also, always quoting the variable is good programming practice; it could > > have whitespace in it, in which case the non-quoted version would expand > > to multiple tokens (and again break). > > > > So, still today, the best defensive way is: > > > > [ "z$WEBALIZER_CRON" != zyes ] > > > > -- > > Chris Adams <cmadams@xxxxxxxxxx> > > Systems and Network Administrator - HiWAAY Internet Services > > I don't speak for anybody but myself - that's enough trouble. > Good to know. Thank you very much, I think we *all* learned something here today :) (actually I finally figured out the reason for this independently, just last month or so. Only took me thirteen years of Linux use...) -- Adam Williamson Fedora QA Community Monkey IRC: adamw | Twitter: AdamW_Fedora | identi.ca: adamwfedora http://www.happyassassin.net -- test mailing list test@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe: https://admin.fedoraproject.org/mailman/listinfo/test
