#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define TRIMSPACES(p) while(*p != '\0' && isspace((unsigned char)*p) != 0) ++p
#define NSTRIP(p, n) p += n
#define STRIP(p) ++p

char* getcode(const char *input, size_t limit)
{
	char *p = (char*) input, *buf, *pbuf;
	size_t i = 0;

	while(*p != '\0') {
		if(strncmp(p, "CODE", 3) == 0) {

		NSTRIP(p, 4); //remove 'code'
		TRIMSPACES(p);//trim all white-spaces after 'code'
		
		/* check we have a '=' after CODE (without spaces).
		   if there is not, returns NULL
		*/
		if(*p != '=') 
			return NULL;
		
		/* ok. We have.. now we don't need of it
			just remove it from we output string.
		*/
		STRIP(p);
		
		/* remove again all white-spaces after '=' */
		TRIMSPACES(p);
		
		/* the rest of string is not valid,
			because are white-spaces values.
		*/
		if(*p == '\0')
			return NULL;
		
		/* allocate space for store the value
			between code= and -.
			this limit is set into second parameter.
		*/
		if((buf = malloc(limit)) == NULL)
			return NULL;

	/* copy the value until found a '-' 
		note: you must be control the size of it, 
	   for don't overflow. we allocated 256 bytes.
		if the string is greater it, do implementation with
		subjecents call to realloc()
	*/
     pbuf = buf;
      while(*p != '\0' && *p != '-' && i < limit) {
		*pbuf ++ = *p++; 
		i ++;
	}
	
	  *pbuf ++ = '\0';
	  return buf;
	}
    p ++;
  }

  return NULL;
}

int 
main(void)
{

char buf[255] = "foo baa CODE =     12345-MODE-12453-CODE-12355";
char *code = getcode(buf,256);

if(code != NULL) {
	printf("code = %s\n", code);
	free(code);
} else {
	printf("Not found code.\n");
}
 return 0;
}

code = 12345