Thread: putting integer in string

How can I put an integer value in a string? something like:

Code:

int a=5;
char string[]=a;
printf("\n%s\n",string);

I tried testing this out as part of a program, and after messing about a bit couldn't get it to work. Even though it compiled, when it ran, no string was printed.

Also, if there is a way, can it be done for integers greater than 1 digit long also?

Originally Posted by bertazoid

How can I put an integer value in a string? something like:

Code:

int a=5;
char string[]=a;
printf("\n%s\n",string);

I tried testing this out as part of a program, and after messing about a bit couldn't get it to work. Even though it compiled, when it ran, no string was printed.

try this:

Code:

#include <stdio.h>

int main(void)
{
    int a = 5;
    char string[32] = "This is my string.";
    
    sprintf(string, "%s %d", string, a);
    printf("%s", string);
    
    return 0;
}

Code:

#include <stdio.h>

int main () {
	int a=97;
	char string=a;
	printf("&#37;c\n",string);
}

You can give an element of a string an integer value.

> sprintf(string, "%s %d", string, a);
Right idea, but the result should go into a separate string.

Very few functions are guaranteed to do the right thing when you're modifying the thing you're reading from.

As Salem points out in post #4: You probably do not want to READ from and WRITE to the same string - you never know what sprintf() does to the input string - it almost certainly doesn't copy it before starting to write to the output string.

--
Mats

Originally Posted by matsp

As Salem points out in post #4: You probably do not want to READ from and WRITE to the same string - you never know what sprintf() does to the input string - it almost certainly doesn't copy it before starting to write to the output string.

--
Mats

Yeh thanks, I missed that when I made my post, and I tried it and it worked. hoorah!

I have a new question, I'm using sprintf sucessfully now, and for what I want to do, the first thing I'm writing to the string is a char e.g:

Code:

sprintf(string,"%c blahblah",char1);

The problem is, this char is declared in a nested if statement, and only in one of the three cases do I want to actually have anything in there. for the other three cases, I want this to be ignored. I tried declaring the char only on this one case, and when the other two cases happened I got a hexagon with a question mark printed, indicating that I'm trying to print a char that hasn't been declared (It did compile).

I also tried using

Code:

char char1=''; //nothing entered

and

char char1=' '; //with space

but the first didn't compile, and the problem with the second is tha I don't want a space...just nothing at all. Is there something else I can use, between the single quotes?..I'd really like to do this without having to add more if/select statements (if possible).


edit: Hmmm, can I use the null character, '\0'?

Originally Posted by bertazoid

Yeh thanks, I missed that when I made my post, and I tried it and it worked. hoorah!

I have a new question, I'm using sprintf sucessfully now, and for what I want to do, the first thing I'm writing to the string is a char e.g:

Code:

sprintf(string,"%c blahblah",char1);

The problem is, this char is declared in a nested if statement, and only in one of the three cases do I want to actually have anything in there. for the other three cases, I want this to be ignored. I tried declaring the char only on this one case, and when the other two cases happened I got a hexagon with a question mark printed, indicating that I'm trying to print a char that hasn't been declared (It did compile).

There are a few ways to solve this problem. Simplest is to set it to '\0' and then check if it's '\0' - in that case, don't print it [putting a '\0' there will make string zero-length, becasuse sprintf isn't clever enough to know that you don't want a '\0' at the beginning of the string and thus make it an empty string].

The second option is to use a char array instead of a single char. An empty string "" will print as "nothing" in sprintf.

The third option is to use different format strings - only put the %c in the format string if it's actually needed - otherwise it will be ignored. Just beware that this ONLY works when it's the last argument(s) of sprintf that you want to skip, there is no way to skip argument 2, but print args 1, 3 and 4. You just have to use different printfs to do that.

--
Mats

Code:

#include <stdio.h>

int main () {

int n=1;
if(n==1){
  char string[]="+"; /* This variable will go away when the block ends */
} /* poof! */
else{
  char string[]=""; /* ditto */
} /* poof! */

printf("&#37;s", string);  /*what variable "string"? */

return 0;
}

For the second, you can never (and by never, we mean never) assign anything to an array. Ever. Of any kind. You can initialize an array at declare time, but you can never assign to it. If you want something to be put into a char array, you can use strcpy.