Question on pointer & files

[Yourhighness]

Hi every one,
I am trying to write a function that deletes a whitespace that seperates the last name followed by a ',' from the first name Initial.
It is part of a compression program that we have to write.

I am having trouble understanding pointers. So if anyone could help me, that would be great.

Here the function I have written so far:

void DelWhiteSpace( char *ptrStr )
{
int i;
char *temp[ strlen( ptrStr ) + 1 ];

*temp = '\0';

for ( i = 0; i < strlen( ptrStr ); ++i )
{
if( isspace( ptrStr[ i ] ) != 0 )
strcat( *temp, strchr( *temp, *( ptrStr + 1 ) ) );
printf( "|%s|\n", temp );
puts( "three" );
}
ptrStr = *temp;
}

My output in cygwin is as follows:

one /*used to identify how far in the main it goes*/
two /*used to identify how far in the main it goes*/
three
three
three
Segmentation fault (core dumped)

Cheers, Johannes

[Hammer]

>>char *temp[ strlen( ptrStr ) + 1 ];
Dynamic sizing of arrays is not supported under C89, only C99 or C++. Which are you coding for?

Also, do you realise that you created an array of pointers, not an array of chars? Did you mean to have (no asterisk)
>>char temp[ LENGTH ];

>>strcat( *temp, strchr( *temp, *( ptrStr + 1 ) ) );
What are you trying to do there? It's bad practice to embed functions like that, if strchr() fails it will return NULL and the program will crash. I suggest you tell us what it is you want this bit of code to do, and then we can guide you better.

Also, please read this

[Yourhighness]

Thanks for the fast reply. The DelWhitespace function is supposed to go through the string, look for the space( ' ' ) and then get rid of the space and concatenate the stirng in a fashion that there is no whitespaces in the string at all.
The Compare function is looking through the string to compare each letter and once the letters of the two strings are not the same anymore, a number representing the count of same lettters, concatenated with the letters different in the string read in last. Ie:

Johnson, F
Johnas, R

is supposed to be written to file like this:

0Johnson,F
4as,R

Cheers,
Johannes

[Hammer]

You can't use strcat() or strchr() in this manner, for this purpose.

Here's a simply way to do this:
Loop through the array, as you find a space, move all the remaining characters left one to cover that space. This will just involve a lot of character swapping on your behalf.

For now concentrate on the DelWhiteSpace function, move on when you've got it right.

[Sebastiani]

If you're just trying to remove whitespace, the idea is to attach two pointers to the
string, one is the iterator, the other the copier. Only increment the copyier if the
undesired char isn't present. Null terminate when done. If you plot it out on a piece
of paper, it will make more sense.

char * stremove(char * string, char remove)
{
 char * iter, * copy = string;

 for(iter = string; *iter != 0; ++iter)
  if(*iter != remove)
   *(copy++) = *iter;

 *copy = 0;

 return string;
}


Which is semantically equivalent to:


char * stremove(char * string, char remove)
{
 char * iter, * copy = string;
 int i, j = 0;

 for(i = 0, iter = string; iter[i] != 0; ++i)
  if(iter[i] != remove)
   copy[j++] = iter[i];

 copy[j] = 0;

 return string;
}


Then it's a simple matter of code reuse:


char * eatwhite(char * string)
{
  return stremove(string, ' ');
}