Re: [PATCH] stat.2: fixed inode printing in example program

["Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>]

Hello Konstantin,

On 9/13/20 9:40 PM, Konstantin Bukin wrote:
> inode numbers are expected to be positive. Casting them to a signed type
> may result in printing negative values. E.g. running example program on
> the following file:
> 
> $ ls -li test.txt
> 9280843260537405888 -r--r--r-- 1 kbukin hardware 300 Jul 21 06:36 test.txt
> 
> resutls in the following output:
> 
> $ ./example test.txt
> ID of containing device:  [0,480]
> File type:                regular file
> I-node number:            -9165900813172145728
> Mode:                     100444 (octal)
> Link count:               1
> Ownership:                UID=2743   GID=30
> Preferred I/O block size: 32768 bytes
> File size:                300 bytes
> Blocks allocated:         8
> Last status change:       Tue Jul 21 06:36:50 2020
> Last file access:         Sat Sep 12 14:13:38 2020
> Last file modification:   Tue Jul 21 06:36:50 2020
> 
> Such erroneous reporting happens for inode values greater than maximum
> value which can be stored in signed long. Printing inode as unsigned
> long long fixes the issue.
> ---
>  man2/stat.2 | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/man2/stat.2 b/man2/stat.2
> index 7e5417480..82eaefcda 100644
> --- a/man2/stat.2
> +++ b/man2/stat.2
> @@ -681,7 +681,7 @@ main(int argc, char *argv[])
>      default:       printf("unknown?\en");                break;
>      }
>  
> -    printf("I\-node number:            %ld\en", (long) sb.st_ino);
> +    printf("I\-node number:            %llu\en", (unsigned long long) sb.st_ino);
>  
>      printf("Mode:                     %lo (octal)\en",
>              (unsigned long) sb.st_mode);

Thanks for your patches and problem report. But, it seems best to 
go with Alejandro's suggestion to use uintmax_t + %ju. See the
patch that Alejandro has sent.

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/