Thread: Writing 64 bit value in hex to a string

  1. #1
    Registered User
    Join Date
    Mar 2006

    Writing 64 bit value in hex to a string

    How do I write a 64 bit value, example
    0xffffffffffffffff to a buffer?
    My code:
    sprintf( buffer , "%016llx\n" , 0xffffffffffffffff ) ;

    This gives me output in buffer as 0x00000000ffffffff.

    An earlier thread suggested using %016llx or %016llX with
    printf to actually print out the output.
    But this does not seem to work with the above function.

    Please help.


  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
      sprintf( buffer , "%016llx\n", 0xffffffffffffffffull ) ;
    You need to explicitly make the constant an unsigned long long
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
    Just Lurking Dave_Sinkula's Avatar
    Join Date
    Oct 2002
    Perhaps this?
    #include <stdio.h>
    #include <stdint.h>
    #include <inttypes.h>
    int main( void )
       unsigned long long value = -1ULL;
       printf("value = 0x%016"PRIX64"\n", value);
       return 0;
    /* my output
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

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