char st1="aviad b aviad";
char st2="aviad";
puts(delete_all_string(st1,st2));

        char str() = "aviad my name is aviad aviad";
	char* strTokHelper = NULL;
	char* output = (char*)malloc(sizeof(str) 1);//output string..you can use a counter and realloc if memory is super important for you
	int flag = 1;//for the first copy	
	strTokHelper = strtok(str," ");
	while(strTokHelper != NULL)
	{
		if(strcmp(strTokHelper,"aviad") != 0)//if they arent identical
		{
			if(flag == 1)//first time you need to copy and not concat
			{
				strcpy(output,strTokHelper);
				flag = 0;//no more copying from now on we will concat
			}
			else
                        {
				strcat(output,strTokHelper);//concating 
                        }
			strcat(output," ");//putting a space between each word
		}
		strTokHelper = strtok(NULL," ");//finding the next word..strTokHelper == NULL -> end of string
	}
	printf("%s\n",output);

char st1[14]="aviad b aviad";
char st2[6]="aviad";
puts(delete_all_string(st1,st2));