how to manipulate char* type in C ?

[namgor]

input: char* a = " i love sharky forum ";
output" char* b = "i love sharky forum";

how do I write a little function to perform manipulation on a to make it become b ??

i tried the following, but returned segmentation fault:

char* trims(char* input) {
   char ret[500];
   int i = 0;

   for (i = 0; i < strlen(input); i++) {
	  if (input[i]!=' ') continue;
	  	strcat (ret, input[i]);
   }

   return ret;
}

Thx~!