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Re: [Help-bash] Passing multiple arrays to a function

From: Jerry
Subject: Re: [Help-bash] Passing multiple arrays to a function
Date: Thu, 13 Dec 2018 05:42:46 -0500

On Tue, 11 Dec 2018 09:15:39 -0500, Greg Wooledge stated:

>On Tue, Dec 11, 2018 at 09:00:24AM -0500, Jerry wrote:
>> I am trying to pass arrays to a function. I can get it to work if I only
>> pass one function; however, I cannot figure out how to pass two or more
>> arrays simultaneously.  
>> ## Call the function
>> standing "address@hidden" "address@hidden"  
>How does your function know where the first list ends, and the second
>list begins?
>If you want to pass two lists to a function on the argument vector,
>you need to pass a special sentinel value as a separator.  This sentinel
>will have to be something that cannot occur in the first list.  Then,
>you'll need to iterate over the argument vector, assigning elements to
>a local array until the special sentinel is found.
>Other approaches may also be considered.  For instance, you can simply
>hard-code the names of the arrays inside the function, and not pass
>them at all.  Or, you could dump the lists into files, and pass the
>names of the files to the function, which can then read the lists from
>the files.  Or, you could pass one list on the argument vector, and
>the other list as a stream on standard input, and have the function
>read the stream into an array.
>Or, if you are especially brave (or foolish), you could attempt to use
>bash 4.3's name reference feature, and pass the names of the arrays
>on the argument vector, and then have the function attempt to use
>namerefs to point to the arrays in the caller's scope.  Be warned that
>doing this will NEVER be 100% safe, because there is no way to prevent
>the caller from passing an array whose name matches one of your
>function's local variables.  And if that happens, shit blows up.
>The best you can do with namerefs is obfuscate the name of every single
>local variable inside the function using some scheme that the caller
>is unlikely to use.  If the caller is malicious, you're just screwed,
>but you can try to minimize the odds of an accident.

Wow, when I started this project, I had no idea that you could not simply
pass multiple arrays, as simply as passing multiple variables to a function.
I am going to have to redesign this script.

Thanks for your help Greg.


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