Fwd: What compiler is doing when we pass unnecessary parameters in scanf

[Aneesh Bhasin <contact.aneesh@gmail.com>]

----forgot to add list as cc------

Hi Kaushik,

any extra non-whitespace, non "%" characters are matched against the
input given from stdin - if they match, it is ignored and if it
doesn't match, no further input is taken.

In case of your second scenario, when you specify "p:%d" as string,
the program expects the input to be of the format "p:<some number>"
but since you give 100 as the input, no value is assigned to the
variable p (you can check the return value of scanf - its zero) and
hence, whatever junk value is in variable p, it is used for further
calculation.

With the second scenario, try giving the input as "p:100" and then p
should get value 100 as expected...

Hope that helps.
Aneesh

On Wed, Jul 29, 2009 at 7:48 PM, RAM_LOCK <Kaushik.Sarkar@netapp.com> wrote:
>
> Hi,
> In the second scenario what value is it printing when i have given extra
> parameter in scanf?
> Does it vary from compiler to compiler?
>
> Scenario : I
> -------------
> root@kaushik_Fedora11 ~/C/LET_US_C/ch-1> cat simple-interest.c
> #include <stdio.h>
>
> void main ()
> {
>        int p;
>        float i=0;
>        printf ("enter the principal amount\n");
>        scanf ("%d",&p);
>        i = (p*5*5)/100;
>        printf ("Interterest is : %f\n",i);
> }
> root@kaushik_Fedora11 ~/C/LET_US_C/ch-1> ./a.out
> enter the principal amount
> 100
> Interterest is : 25.000000
>
>
> Scenario : II
> -------------
> > cat simple-interest.c
> #include <stdio.h>
>
> void main ()
> {
>        int p;
>        float i=0;
>        printf ("enter the principal amount\n");
>        scanf ("p:%d",&p);
>        i = (p*5*5)/100;
>        printf ("Interterest is : %f\n",i);
> }
> root@kaushik_Fedora11 ~/C/LET_US_C/ch-1> ./a.out
> enter the principal amount
> 100
> Interterest is : -9321198.000000
>
> --
> View this message in context: http://www.nabble.com/What-compiler-is-doing-when-we-pass-unnecessary-parameters-in-scanf-tp24719839p24719839.html
> Sent from the linux-c-programming mailing list archive at Nabble.com.
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html