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inttypes.h

C also provides placeholders for printf() and scanf() in the header file inttypes.h for the four classes of integer types defined in stdint.h.

  • Fixed-width integer types, such as int8_t.
  • Minimum width integer types, e.g. int_least8_t.
  • Fastest minimum width integer types, e.g. int_fast8_t.
  • Maximum width integer type, e.g. intmax_t.

The placeholder for printf() takes the form PRI + raw placeholder + type keyword/width. For example, if the original placeholder is %d, the corresponding placeholder would be as follows.

  • PRIdn (fixed-width type)
  • PRIdLEASTn (minimum width type)
  • PRIdFASTn (fastest minimum width type)
  • PRIdMAX (maximum width type)

The n in the above placeholder can be substituted with 8, 16, 32 or 64.

Here is an example of usage.

#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>

int main(void) {
  int_least16_t x = 3490;
  printf("The value is %" PRIdLEAST16 "! \n", x);
}

In the above example, PRIdLEAST16 corresponds to an integer of type int_least16_t with the original placeholder %d. Also, the first argument to printf() uses the automatic merging of multiple strings.

Here are the other placeholders corresponding to the original placeholder.

  • %i: PRIin PRIiLEASTn PRIiFASTn PRIiMAX
  • %o: PRIon PRIoLEASTn PRIoFASTn PRIoMAX
  • %u: PRIun PRIuLEASTn PRIuFASTn PRIuMAX
  • %x: PRIxn PRIxLEASTn PRIxFASTn PRIxMAX
  • %X: PRIXn PRIXLEASTn PRIXFASTn PRIXMAX

The placeholder rules for scanf() are similar.

  • %d: SCNdn SCNdLEASTn SCNdFASTn SCNdMAX
  • %i: SCNin SCNiLEASTn SCNiFASTn SCNiMAX
  • %o: SCNon SCNoLEASTn SCNoFASTn SCNoMAX
  • %u: SCNun SCNuLEASTn SCNuFASTn SCNuMAX
  • %x: SCNxn SCNxLEASTn SCNxFASTn SCNxMAX