Find a substring in the given text .. C-program

Question

char *substring(char *text, int position, int length)
{
   int i, j=0;
   char *temp ;

   for(i=position-1; i<position+length-1; i++)
   {
     temp[j++] = text[i];
   }
   temp[j] = '\0';

   return temp;
}

Hi What is the error in the following code. I am trying to run this on Fedora Machine. And that gives me an error at runtime "Segmentation Error". What is this error? .. and why does it give this error.

Thank..

Answer 1

You need to allocate memory for temp- at the moment, this is just dangling pointer. You can use mallocfor this, but note that the caller will need to ensure that this storage is subsequently freed.

For instance:

char *substring(const char *text, int position, int length)
{
   char *temp = malloc(length + 1);
   int i, j;

   for (i = position, j = 0; i < position + length; i++, j++)
   {
       temp[j] = text[i];
   }
   temp[j] = '\0';

   return temp;
}

Answer 2

temp uninitialized.

Answer 3

, - , , , .

, temp , , .

length + 1, , , , .

, static ( ), :

if((temp = malloc(length + 1)) == NULL)
  return NULL;

Answer 4

- , .

, ,

1. use C strstr(...)
2. Robin-Karp method
3. Knuth-Morris-Pratt method
4. Boyer Moore method

Update: , ( ). , strchr().

Answer 5

, .

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..

Answer 6

, , / * temp. .

malloc, strdup, . , strncpy (null terminate), .