Re: if [[ $Something ]] – in what situations does this work?

[Johnny Rosenberg]

2012/2/18 franz.reitinger <franz.reitinger at htl-wels.at>:
> First of all I suppose you're using the bash.

Yes, sorry for not mentioning that.

> Amoung others the shell treats several parameters specially; these
> parameters may only be referenced and assignement to them is not allowed.

But I didn't assign anything to it, did I?

>
> One of them is $?, which expands to the exit status of the most recently
> executed command. However, the exit status 0 means that the command has been
> executed without errors; any other return value has to be interpreted as
> error code.

Yes, but [[ $? ]] returns the same result no matter the value of $?,
so [[ $Something ]] doesn't seem to be a valid syntax, is it? Maybe I
just confuse bash scripting with other things, such as C and even
Basic:
if (x) {
	dostuff;
	domorestuff;
}

or

if x then
	dostuff
	domorestuff
endif


> e.g.
> # any command ...
> if [ $? -ne 0 ]; then
>   # error handling
> fi

I suppose ”if [[ $? == 0 ]]” is equal to ”if [ $? -ne 0 ]”, right? And
I think that even ”if [[ $? = 0 ]]” is allowed and means the same
thing, as far as I have seen.


Kind regards

Johnny Rosenberg
ジョニー・ローゼンバーグ


>
> /franzR
>
> On Sat, 18 Feb 2012 13:56:50 +0100, Johnny Rosenberg wrote:
>>
>> I tried this with the $? variable, but failed. Seems like [[ $? ]] is
>> always true no matter the value of $?. [[ $? == 0 ]] seems to work,
>> though.
>>
>> I thought that ”if [[ $? ]]” means ”if $? is True”. What is True
>> anyway? 0? 1? Anything but 0?
>>
>> I am not sure what I am asking for here, but any kind of input in the
>> subject is welcome. Thanks.
>>
>>
>> Kind regards
>>
>> Johnny Rosenberg
>> ジョニー・ローゼンバーグ
>
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