Greetings, Eric Blake! >>>>> [ ... -a ... ] is not portable; there are some inherently ambiguous >>>>> situations that it cannot handle. POSIX recommends that you spell it [ >>>>> ... ] && [ ... ] instead. >>>>
>> >> If a script author did not quote the indirect references, it is their fault, > No, even with proper quoting, the use of -a and -o creates ambiguous > situations. For example, a naive read would claim that > test "$var1" -a "$var2" > sets $? to 0 only if both "$var1" and "$var2" are non-empty. But > according to the POSIX rules, if $var1 is '!' and $var2 is '', then this > MUST be treated as the negation of the unary operator '-a "$var2"', if > the shell has a unary -a (bash does, dash does not). And in bash's > case, '-a ""' is false (the empty string never exists as a file), so the > negation is true, and you have a case where the -a version returned 0 in > spite of one of the inputs being empty. That's... great. At the very least, we have a standard we can rely... refer... to... >.< sigh. Thanks for your thorough explanation, much appreciated! (And I have a set of scripts to rewrite...) -- With best regards, Andrey Repin Friday, September 11, 2015 04:58:51 Sorry for my terrible english... -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
