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, C.Sava -- test mailing list test@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe: https://admin.fedoraproject.org/mailman/listinfo/test
