Учи баш, учи баш

[amarao]

Вот, я опять узнал что-то новое.

! command позволяет инвертировать код возврата. Казалось бы, тривиально, но с учётом мнения readline по поводу '!' у меня было табу насчёт восклицательных знаков в шелле.

Comments

[juan_gandhi]

OMG. It's complicated, is not it? How do they keep 42? Seems like the script is compiled (and optimized) before running. Weird, weird. Not that I don't like it. Enjoying it.

[ex0_planet]

Yep, it is more complicated than I thought it would be.

Compiled? Not necessarily, IMO they have some sort of expression context (kinda like Perl, after all it is from the same era :)). So, a '! ! 42' evaluates in some sort of numeric context (there is an implicit assignment to $!); in the context of 'if .. then' expression it is evaluated as boolean. Makes sense, huh!?

[juan_gandhi]

Yes, but one had to reduce ! ! to nop, otherwise how does it know that ! 0 should be 42?