itoa() — Convert int into a string

Standards

Standards / Extensions	C or C++	Dependencies
z/OS® UNIX	both	z/OS V1R5

Format

#define _OPEN_SYS_ITOA_EXT
#include <stdlib.h>

char * itoa(int n, char * buffer, int radix);

General description

The itoa() function coverts the integer n into a character string. The string is placed in the buffer passed, which must be large enough to hold the output. The radix values can be OCTAL, DECIMAL, or HEX. When the radix is DECIMAL, itoa() produces the same result as the following statement:

(void) sprintf(buffer, "%d", n);

with buffer the returned character string. When the radix is OCTAL, itoa() formats integer n into an unsigned octal constant. When the radix is HEX, itoa() formats integer n into an unsigned hexadecimal constant. The hexadecimal value will include lower case abcdef, as necessary.

Returned value

String pointer (same as buffer) will be returned. When passed a non-valid radix argument, function will return NULL and set errno to EINVAL.

Portability considerations

This is a non-standard function. Even though the prototype given is commonly used by compilers on other platforms, there is no guarantee that this function will behave the same on all platforms, in all cases. You can use this function to help port applications from other platforms, but you should avoid using it when writing new applications, in order to ensure maximum portability.

Example

CELEBI12

/* CELEBI12

   This example reads an int and formats it to decimal, unsigned
   octal, and unsigned hexadecimal constants converted to a
   character string.

*/

#define _OPEN_SYS_ITOA_EXT
#include <stdio.h>
#include <stdlib.h>

int main ()
{
   int i;
   char buffer [sizeof(int)*8+1];
   printf ("Enter a number: ");
   if (scanf ("%d",&i) == 1) {
      itoa (i,buffer,DECIMAL);
      printf ("decimal: %s\n",buffer);
      itoa (i,buffer,HEX);
      printf ("hexadecimal: %s\n",buffer);
      itoa (i,buffer,OCTAL);
      printf ("octal: %s\n",buffer);
   }
   return 0;
}

Output

If the input is 1234, then the output should be:

decimal: 1234
hexadecimal: 4d2
octal: 2322