Thread: using return from UNIX command

Well, I really tried to avoid this, but... I searched all over the place, looked at tutorials, etc., but I can't find an example of how to do what I'm trying to do. It could be because I'm going about it all wrong; I'll be the first to admit I'm pretty green.

I am trying to take the return from the UNIX "uptime" command, get the three float numbers and the end, and average them. It's mostly an exercise (I need to write a bunch of stuff interacting with the OS and until I can figger this out, I can't).

I know that if I do:

char upt[80];
*upt = system("uptime");
printf("%s\n", upt);

I can print the whole line, which resembles:

1:14pm up 99 days, 2:49, 32 users, load average: 0.17, 0.37, 0.35

What I'm trying to do, misguided or not, is to load that information somehow into a struct, convert the salient items from the struct to float, then do the average. What I cannot do is figure out how to get it into the struct. I've learned that a struct is not an lvalue, so I can't simply load the info directly to the struct. So, am I wasting my time, and should I be doing something else based on string operations? Silly kindergarten code follows, please don't whip me :

Code:

#include <stdlib.h>
#include <stdio.h>

/*
Return from UNIX "uptime" command appears generally as follows:
  1:14pm  up 99 days,  2:49,  32 users,  load average: 0.17, 0.37, 0.35
*/

float a = 0;
float b = 0;
float c = 0;
float d = 0;

typedef struct
{
   char filler_a[55];
   char first[4];
   char filler_b[2];
   char second[4];
   char filler_c[2];
   char third[4];
}inforec;


int main()
{

   inforec numbers;
   *numbers = system("uptime");  /* Where I'm going wrong */


   a = atof(numbers.first);
   b = atof(numbers.second);
   c = atof(numbers.third);
   d = (( a + b + c ) / 3 );

   printf("----------------\n");
   printf("FIRST:   %1.2f\n", a);
   printf("SECOND:  %1.2f\n", b);
   printf("THIRD:   %1.2f\n", c);
   printf("-------\n");
   printf("AVERAGE: %1.2f\n\n", d);

   return(0);
}

I'm not asking for code; don't think I'm asking anyone to write something. Just looking for advice and suggestions on where I'm missing the boat here. Thanks!

djp

vVv,

Thank you, that is exactly what I needed. Sorry about the mis-post, I'll go play on the other board. Great FAQ, btw, lots of helpful stuff.

djp