extracting token from a string

Hello everyone,

below is my code.  I try to extract a token in the a string, but i get stuck at the next token function.
can anyone help me out with this problem.
thanks

the error i got after i compiled and ran is
subString.c(36) : error C2106: '=' : left operand must be l-value


#include<stdio.h>
#include<string.h>
#define SIZE 100


// Function Prototype

void getInput(char line[]);
int isDelimiter(char letter);
int skipDelimiters(int startPos);
int scanToken(int startPos);
char *nextToken(char token[]);
char *subString(char token[], char inputString[], int start, int cPos);


// Global Variable

char inputString[SIZE];
int maxPos;


// Starting program

int main(void)
{
      
      //int len;
//      int startPos = 0;
//      int lasPos = 3;
      char token[20];
      
      getInput(inputString);

      maxPos = strlen(inputString);

      token = nextToken(inputString);
      printf("length of array %d", strlen(inputString));

      //printf("\n\n%s \n\n", subString(token, inputString, startPos, lasPos));


      return 0;
}


//////////////////////////////////////////////////////////////////////////////
// subString
char *subString(char token[], char inputString[], int start, int cPos)
{

      for(start; start < cPos; start++)
    {
         
          if(start < cPos)
          {
               token[start] = inputString[start];
          }
    }
     token [start] = '\0';

      return token;
}


/////////////////////////////////////////////////////////////////
// getInput function
//----------------------------------------------
void getInput(char line[])
{
      int i = 0;
      while(i < 81 && (line[i++] = getchar()) != '\n')
      ;

      line[i] = '\0';

}


/////////////////////////////////////////////////////////////////
// skipDelimiters function
//----------------------------------------------
/*
      skips delimiters starting from the specified
      position.        Return the index of the first
      non-delimiter character at or after startPos

*/
int skipDelimiters(int startPos)
{
      int position = startPos;
      while(position < maxPos)
      {
            char c = inputString[position];
            
            if(!isDelimiter(c))
            {
                  break;
            }

            position++;
      }
      return position;
}

////////////////////////////////////////////////////////////////
// scanToken function
//----------------------------------------------
/*
      Skips ahead from starPos and returns the index
      of the next delimiter character encountered, or
      maxPos if no such delimiter is found.

*/
int scanToken(int startPos)
{
      int position = startPos;
      while(position < maxPos)
      {
            char c = inputString[position];
            
            if(isDelimiter(c))
            {
                  break;
            }

            position++;
      }
      return position;
      
}


///////////////////////////////////////////////////////////////////
// nextToken function
//----------------------------------------------
/*
      Return next token from the String.

*/
char *nextToken(char token[])
{
      int currentPosition;
      int start;

      currentPosition = skipDelimiters(currentPosition);
      if(currentPosition >=maxPos)
      {
            return 0;
      }

      start = currentPosition;
      currentPosition = scanToken(currentPosition);
      token = subString(token, inputString, start, currentPosition);

      return token;

}

////////////////////////////////////////////////////////////////////
//----------------------------------------------
int isDelimiter(char letter)
{
      char delimiters[] = {' ', ',', '\r', '\n', 0};
      
      int valid = 0;
      int i = 0;

      while(letter != delimiters[i])
      {
            valid = 0;
            i++;
      }

      if(letter == delimiters[i])
      {
            valid = 1;
                  
      }

      return valid ;
}