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

[Robert P. J. Day]

On Sat, 18 Feb 2012, franz.reitinger wrote:

> First of all I suppose you're using the bash.
> Amoung others the shell treats several parameters specially; these
> parameters may only be referenced and assignement to them is not
> allowed.
>
> 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.
> e.g.
> # any command ...
> if [ $? -ne 0 ]; then
>     # error handling
> fi

  i'd have to check but i think the constuct

  if [[ $VAR ]]

does nothing but check if either that variable is defined, or if it
has a non-zero string length.  so no matter what the value of $? is,

  if [[ $? ]]

will always evaluate to true.  you should verify that yourself,
though.

  if you're checking the returned value of $?, you should always
compare it explicitly.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

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