Convert numbers with toString in Ansi C

Question

Is it possible to use toString operator, or how to convert numbers to char arrays.

Answer 1

int myNumber = 27; /* or what have you */
char myBuffer[100];
snprintf(myBuffer, 100, "%d", myNumber);

There are several considerations for you to think about here. Who provides the memory to hold the string? How long do you need it for, etc? (Above it's a stack buffer of 100 bytes, which is way bigger than necessary for any integer value being printed.)

Best answer: start using Java. Or Javascript, or C#, or for the love of God almost anything but C. Only tigers lie this way.

Answer 2

Use the sprintf() function.

Answer 3

sprintf() is considered unsafe because it can lead to a buffer overflow. If it's available (and on many platforms it is), you should use snprintf() instead. Consider the following code:

#include <stdio.h>
int main()
{
    int i = 12345;
    char buf[4];
    sprintf(buf, "%d", i);
}

This leads to a buffer overflow. So, you have to over-allocate a buffer to the maximum size (as a string) of an int, even if you require fewer characters, since you have the possibility of an overflow. Instead, if you used snprintf(), you could specify the number of characters to write, and any more than that number would simply be truncated.

#include <stdio.h>
int main()
{
    int i = 12345;
    char buf[4];
    snprintf(buf, 4, "%d", i);
    //truncates the string to 123
}

Note that in either case, you should take care to allocate enough buffer space for any valid output. It's just that snprintf() provides you with a safety net in case you haven't considered that one edge case where your buffer would otherwise overflow.