Re: [LIP] Avoid use of global variables

Kumar Appaiah wrote:

> 
> Now, I wish to add a feature by which I can allow several files in a
> directory tree to be processed. I, therefore, use the ftw function
> (nftw variant). However, notice that I now have to call my process
> file function from the "callback" function for nftw:
> 
> static int
> ftw_handler(const char *fpath, const struct stat *sb,
>             int tflag, struct FTW *ftwbuf)
> {
>   /* ... */
> 
>   processFile(filename, <variables which depend on command line arguments>);
>   /* ... */
>   return 0;
> }
> 
> int
> main(int argc, char *argv[])
> {
>   /* Get command line parameters */
>   /* ... */
> 
>   if (nftw((argc < 2) ? "." : argv[1], ftw_handler, 20, flags)
>       == -1) {
>     perror("nftw");
>     exit(1);
>   }
>   /* ... */
>   return 0;
> }
>  
> My question is, how do I pass on the elements of the command line
> arguments which alter the behaviour of processFile while calling it?
> It seems to me that the easiest way would be to use global variables,

Yes.

> but is there an elegant way by which this can be avoided? Or, is it
> acceptable to use global variables in this situation?

Usually callbacks accept a void *mystuff style context object to solve 
this exact problem. Since nftw() doesn't let you pass in a context 
object I don't see how you can avoid using globals.

Also using globals is not a bad thing - particularly in write once, read 
many cases.

srp
-- 
http://saju.net.in

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