Thread: Append an integer to a char * as a count

MilleniumFalcon has your solution for "int to string".

Your description of what you really need for "desk1", "desk2", ... is a little unclear. Perhaps you should look into arrays: Arrays in C - Cprogramming.com. If that's not what you're looking for, perhaps you could show us some code, or pseudo code to better illustrate your problem.

Thank you for the replies. I have not used macros a great deal in the past but I will certainly look into them. Let me see if I can clarify a little more though. I just am curious to know if there is a way I could concatenate an integer onto a string while still keeping the string format (by string I mean char[]). I have had many instances lately where this would have helped so its for more than this example exclusively. This is what I'm after, although I know this doesn't work.

int n = 99;
char * str = "vote";
char * newstr = strcat(str, n);

I do not know how to convert the n to a string in order to accomplish this.

Thanks!

So, in order for you to actually write to a string, you have to have writable memory. A string literal (a.k.a. string constant) is not writable -- it's constant, unchanging. Thus, you can't do

Code:

char *foo = "some stuff";
strcat(foo, "more stuff");

What you do is declare an array that is large enough to hold the largest string you need (+1 for the terminating null character), and use sprintf as Tim suggested:

Code:

char my_string[17];
sprintf(my_string, "vote%d", 42);

But I would be remiss if I didn't mention two excellent improvements to the above code: defining a constant for the string length, and using snprintf (documentation). The 'n' is the version that limits how much it writes into your string so you don't overflow it.

Code:

#define MAX_STR_LEN 100
...
// in a function because global variables are evil
char my_string[MAX_STR_LEN + 1];  // +1 for the null terminator
snprintf(my_string, sizeof(my_string), "vote%d", 42);

Bonus: notice that I used sizeof(my_string) for the size of my_string, instead of MAX_STR_LEN. Imagine you wanted to change my_string to be of size SOME_OTHER_CONSTANT. If I used MAX_STR_LEN in the snprintf call, I would have to remember to change it -- and I might forget, leaving open the possibility of an overflow. Using sizeof will always give the right size.