need C help, passing char buffer[] by-value....

Tue Oct 20 03:24:55 UTC 2009

Gary Kline wrote:
> On Mon, Oct 19, 2009 at 11:09:19AM -0700, Patrick Mahan wrote:
>> See comments interspaced below -
>>
>> Gary,
>>
>> Let me restate your problem: You want to read through a file containing tags
>> delimited by "<>" and to skip these tags if the user has run your command 
>> with
>> the "-N" flag.
>>
>> In C any thing passed by address is "by reference".  For a your static 
>> buffer
>> of 1024 characters: you can pass it by reference as:
>>
>>            skiptags(buf); /* passes in the starting address of the buffer */
>>            skiptags(&buf[0]); /* passes in the starting address of the 
>>            buffer */
>>            skiptags(&buf[10]); /* passes int the starting address of the 
>>            buffer
>>                                   at the 11th character position. */
>>
>> Arrays and pointers are always by reference.  Individual data types "int",
>> "char", etc are by value unless passed in as a pointer.  I think this is 
>> where
>> your confusion is around.
> 
> 
> 	You've got it exactly right, Patrick.  There were no "C" classes in 1978--I 
> 	taught myself.  Obviously, not that well because I have already dreaded 
> 	pointers.  ---Well, usually.

You are welcome, glad to help.

[examples snipped]

> 
> 
> 	Your examples help a lot!   Everything works except when there are two or more 
> 	tags on one line such as:
> 
> 	<BODY BGCOLOR="#FFFFFF" LINK="#00FFFF" VLINK="#006633"><FONT SIZE="4">
> 
> 
> 	I think I see where is your skiptags--pointer arithematic function--this can be
> 	caught.  Thanks much!
>

If I might make a suggestion.  Make use of a case (switch) statement:

         switch(buf[c]) {
             case '<': /* start of tag, skip it if requested */
                  if (skiptags) c = skiptag(&buf[c]);
                  ...

             default: /* handle normal stuff */
                   ...
         }

Inside your while() statement.

Good luck,

Patrick