Searching for partial strings

[Sinensis]

I have an array of structures called STUDENTs that has student names in it, and I need to be able to search this array for partial student names and get back full student records.

For example I need to be able to search for "Mercury, Fred" and get back a student record as well as be able to search for "M" and get back all names starting with "M."

This is the function I have for it:

int nSearch(STUDENT ary[], int size, char key[])
{
	int i;
	int results = 0;
	
	for(i = 0; i < size; i++)
	{
		if(strncmp(key, ary[i].name, sizeof(key)) == 0) 
		{
			printf("\n+---------------------+--------+--------+--------+--------+--------+---------+-------+\n");
			printf("| Student Name        |  ID    | Test 1 | Test 2 | Proj 1 | Proj 2 | Average | Grade |\n");
			printf("+---------------------+--------+--------+--------+--------+--------+---------+-------+\n");
			printf("| %-20s| %6d |%5d   |%5d   |%5d   |%5d   |%8.2f |   %-2s  |\n", ary[i].name, ary[i].id, 
				ary[i].s1, ary[i].s2, ary[i].s3, ary[i].s4, ary[i].avg, ary[i].grade);
			results++;
		}
	}
	if (results > 0) printf("+---------------------+--------+--------+--------+--------+--------+---------+-------+\n");
	if (results == 0) return 0; //no match
}

Obviously not working. Anyone know what I can go?

[zacs7]

int nSearch(STUDENT ary[], int size, char key[])
...
if(strncmp(key, ary[i].name, sizeof(key)) == 0)

Remember that key is a pointer (same as writing, char * key). So sizeof() will usually return 4 (or 8 now 64-bit machines are coming popular ). Use strlen() instead which you should call once at the start of the function... ie

int nSearch(STUDENT * arry, size_t n, const char * key)
{
   size_t len = strlen(key);
   size_t i = 0;

   for(i = 0; i < n; i++)
   {
      if(strncmp(arr[i].name, key, len) == 0)
      {
         /* match */ 
      }
   }
}

[Sinensis]

int nSearch(STUDENT ary[], int size, char key[])
...
if(strncmp(key, ary[i].name, sizeof(key)) == 0)

Remember that key is a pointer (same as writing, char * key). So sizeof() will usually return 4 (or 8 now 64-bit machines are coming popular ). Use strlen() instead which you should call once at the start of the function... ie

int nSearch(STUDENT * arry, size_t n, const char * key)
{
   size_t len = strlen(key);
   size_t i = 0;

   for(i = 0; i < n; i++)
   {
      if(strncmp(arr[i].name, key, len) == 0)
      {
         /* match */ 
      }
   }
}

worked perfectly. I certainly appreciate it.

[Salem]

But isn't strncmp() where n = strlen() of one of the strings, just the same as strcmp() ?

[matsp]

But isn't strncmp() where n = strlen() of one of the strings, just the same as strcmp() ?

No, only if n is the length of the LONGER of the strings. strncmp() will MATCH (return 0) if the strings match upto len, even if the longer string continues. E.g.

strncmp("Allan", "All", 3);

will return 0.

--
Mats