Help Adding a CHAR to the end of a STRING

[MicroBlaze]

//====================================================

int main (void) {

   printf("------------------------------------------------\r\n");
   printf("-- Entering main() --\r\n");
   printf("------------------------------------------------\r\n");


  /* Help... after 3 hours I need some help...  I want to take a char
   and add it to the end of a string.  and then be able to print the 
   new string with a standard printf.  Here is a snip of the code I 
   can't get to work... */

// 16 char string that will later be sent to a 2x16 LCD display 
  char LCDString[16] = "Switch = "; 

  char dipSwitch1;
  char dipSwitch2;  
  dipSwitch1 = '6';
  dipSwitch2 = '3';
  printf("the value of the dipSwitches are %c and %c \r\n", dipSwitch1,dipSwitch2);
// This does print the text "the value of charOnes is 6"
// Now I want to take charOnes and add it to the end of the string LCDString
// strcat only seems to work when I has 2 text strings like the following
  char str[80];
  strcpy (str,"strings  ");
  strcat (str,"have been ");
  strcat (str,"concatenated.");
  printf("%s \r\n",str);
/* But what I want is something like strcat (LCDString, charOnes)... 
  but this does not work.  charOnes ends up as odd charachers 
  like "¨°0" or some other unprintable thing... and it seems to 
  change based on the number of lines in my code... so I think I'm 
  getting some pointer or address of what I really want... help  */
  char str2[16];
  strcpy (str2,"Switch =  ");
  strcat (str2,dipSwitch1);
  printf("%s \r\n",str2);
// I want the string to be "Switch = 6"
  strcat (str2,dipSwitch2);
  printf("%s \r\n",str2);
// now I want it to be I want the string to be "Switch = 63"

   printf("------------------------------------------------\r\n");
   print("-- Exiting main() --\r\n");
   printf("------------------------------------------------\r\n");
   return 0;
}

[redhead]

Look at sprintf() or snprintf() depending on what is supported on your system.

[MicroBlaze]

is there a smaller way to do this? my system is an embedded system and I don't have much memory. I just tried sprintf() and it's too big. Is there a way to do this without using sprintf(). For example, I'm wrote a function hex2char(num) where I just do an if else and assign a char for 0 through F. Then I have another function that can take any number and split it into it's individual digits, where 243 would get changed to 2,4,3 then I change each to the char '2','4','3'. now I what to just stick the char '2','4','3' into a string 243. I need the do this with the smallest amount of compiled code... Any better ideas?

[redhead]

You need to be sure, theres room for the addition in the resulting char* if you just want to add it.
Something like this would do:

#include <stdio.h>
#include <string.h>
#define LENGTH 80
int main(){
    char str[LENGTH +1];
    strncpy(str, LENGTH, "Something = ");
    printf("%s\n", str);
    if(strlen(str) < (LENGTH -1))
    {  /* add a char */
        str[strlen(str)] = '3';
        str[strlen(str)] = '\0';
    }
    printf("%s\n", str);
    return 0;
}

But you need to be sure, that you've already assigned enough memory to your string, befor the addition, and that you NULL terminates the string, else your program will have uncontrolable behavior.
But the memory failure will only occur when you dont know what you're doing, you could easily free() the previusly used memory after your snprintf() and have that available instead of using alot and never free it.
ie:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define LENGTH 80

int main(){
    char *str1, *str2;
    str1 = (char*)malloc(LENGTH*sizeof(char));
    str2 = (char*)malloc(LENGTH*sizeof(char));
    if(str1 != NULL)
        strncpy(str1, LENGTH, "Somethign = ");
    printf("%s\n", str1);
    if(str2 != NULL)
        if(strlen(str1) < LENGTH)
            if(sprintf(str2, "%s%c", str1, '3'))
              free(str1);
              /* memory previusly occupied by str1 
               * is now free to be used elsewhere */
    printf("%s\n", str2);
    free(str2);
    /* memory previusly occupied by str2 
     * is now free to be used elsewhere */
    return 0;
}