[GNHLUG] Silly C/C++ question...

[Ric Werme]

> I am sure I will kick myself when I find out the answer, but...
> 
> I have a text file that for now consists of 3 lines, later it will have
>   data.
>   line 1: integer representing the array size
>   line 2: four doubles separated by commas
>   line 3: \n
> 
> Here is the code fragment that I have been trying to get to work.  I have
> no idea why I am getting the output I am.

Here are the juicy lines:

> fscanf(fp, "%i", &N);             // Find file length ==> read first line

1) Use printf control strings.  "%d\n" might work.
2) You're looking at your file as a bunch of lines.  (You probably edit
   with vi.)  A Unix file is a bag o' bytes.  Be sure to have fscanf read
   and discard the \n.  May not be necessary, actually.  If you're expecting
   a bunch of lines, you should read the file a line at a time and parse
   that.

> fscanf(fp, "%d%d%d%d", &fstart1, &fend1, &M1, &dt1);     // get fstart, ...
3) Add commas to step over commas.  The number parser will skip white
   space.
4) It's a very good idea to check the return value from scanf.  It returns
   when it can't parse the data and the item count gives you good clues.

My code:
#include <stdio.h>

main() {
    char buf[4097];
    int size;
    double w, x, y, z;
    FILE *fp;
    int num;

    fp = fopen("foo.bruce", "r");
    fgets(buf, sizeof(buf), fp);
    num = sscanf(buf, "%d", &size);
    printf("%d: size %d\n", num, size);

    fgets(buf, sizeof(buf), fp);
    num = sscanf(buf, "%lf,%lf,%lf,%lf", &w, &x, &y, &z);
    printf("%d: %6.4lf %6.4lg %6.4lf %6.4lf\n", num, w, x, y, z);

    fgets(buf, sizeof(buf), fp);
    num = sscanf(buf, "");	/* Pointless */
    printf("%d: %x\n", num, buf[0]);
}

My data:
666
0, 5e-10,2.7182, 3.14159

My output:
tux:c> ./bruce
1: size 666
4: 0.0000  5e-10 2.7182 3.1416
0: a