Thread: Please Help Reading Data From A File

Code:

int foo;
while( (foo = fscanf( ...all this stuff... )) != EOF )
{
    if( foo == numberofconversionsyouexpect )
    {
        ...do something...
    }
    else
    {
        ...incorrect number of conversions, handle your error somehow...
    }
}

Something like this perhaps?

Quzah.

Sorry, I just like playing with [fs]scanf.

Code:

#include <stdio.h>

int main(void)
{
   FILE *file = fopen("cond.inp", "r");
   if ( file )
   {
      int h;
      char conname[20];
      float conconc;
      double conrho, conmw, conprod, C, D, A, B;
      while ( fscanf(file, "Number: %d Species: %19s Concentration: %e "
                     "Density: %lf Molecular Weight: %lf Production Rate: %lf "
                     "Saturation Vapor Pressure%*[^:]: C=%lf D=%lf "
                     "Surface Tension%*[^:]: A=%lf B=%lf ",
                     &h, conname, &conconc, &conrho, &conmw, 
                     &conprod, &C, &D, &A, &B) == 10 )
      {
         printf("Number: %d\n"
                "Species: %s\n"
                "Concentration: %e\n"
                "Density: %f\n"
                "Molecular Weight: %f\n"
                "Production Rate: %f\n"
                "Saturation Vapor Pressure: C=%f D=%f\n"
                "Surface Tension: A=%f B=%f\n\n",
                h, conname, conconc, conrho, conmw, conprod, C, D, A, B);
      }
      fclose(file);
   }
   return 0;
}

/* my output
Number: 1
Species: first
Concentration: 1.000000e+14
Density: 4.000000
Molecular Weight: 1.000000
Production Rate: 1.000000
Saturation Vapor Pressure: C=1.000000 D=1.000000
Surface Tension: A=1.000000 B=0.000000

Number: 2
Species: second
Concentration: 1.000000e+14
Density: 2.000000
Molecular Weight: 1.000000
Production Rate: 1.000000
Saturation Vapor Pressure: C=1.000000 D=1.000000
Surface Tension: A=1.000000 B=0.000000

Number: 3
Species: third
Concentration: 1.000000e+14
Density: 1.000000
Molecular Weight: 1.000000
Production Rate: 1.000000
Saturation Vapor Pressure: C=1.000000 D=1.000000
Surface Tension: A=1.000000 B=0.000000

Number: 4
Species: fourth
Concentration: 1.000000e+14
Density: 4.000000
Molecular Weight: 1.000000
Production Rate: 1.000000
Saturation Vapor Pressure: C=1.000000 D=1.000000
Surface Tension: A=1.000000 B=0.000000
*/

Originally Posted by NickHolmes

1) If I want to save the parameters in a series of arrays how do I include it? tried aa[h]=conrho; ab[h]=conmw; etc
but it gave me an error when run.

I'd recommend a single array of a structure containing all common data.

Code:

#include <stdio.h>

struct con
{
   int    h;
   char   name[20];
   float  conc;
   double rho, mw, prod, C, D, A, B;
};

struct con mycon[5];

int main(void)
{
   FILE *file = fopen("cond.inp", "r");
   if ( file )
   {
      size_t i, j;
      for ( i = 0; i < sizeof mycon / sizeof *mycon; ++i )
      {
         if ( fscanf(file,
                     "Number: %d "
                     "Species: %19s "
                     "Concentration: %e "
                     "Density: %lf "
                     "Molecular Weight: %lf "
                     "Production Rate: %lf "
                     "Saturation Vapor Pressure%*[^:]: C=%lf D=%lf "
                     "Surface Tension%*[^:]: A=%lf B=%lf ",
                     &mycon[i].h,
                     mycon[i].name,
                     &mycon[i].conc,
                     &mycon[i].rho,
                     &mycon[i].mw,
                     &mycon[i].prod,
                     &mycon[i].C, &mycon[i].D,
                     &mycon[i].A, &mycon[i].B) != 10 )
         {
            break;
         }
      }
      fclose(file);
      for ( j = i, i = 0; i < j; ++i )
      {
         printf("Number: %d\n"
                "Species: %s\n"
                "Concentration: %e\n"
                "Density: %f\n"
                "Molecular Weight: %f\n"
                "Production Rate: %f\n"
                "Saturation Vapor Pressure: C=%f D=%f\n"
                "Surface Tension: A=%f B=%f\n\n",
                mycon[i].h,
                mycon[i].name,
                mycon[i].conc,
                mycon[i].rho,
                mycon[i].mw,
                mycon[i].prod,
                mycon[i].C, mycon[i].D,
                mycon[i].A, mycon[i].B);
      }
   }
   return 0;
}

Originally Posted by NickHolmes

2) Why do you have

"Number: %d Species: %19s Concentration: %e "
and
"Density: %lf Molecular Weight: %lf Production Rate: %lf "
on separate lines. I tried it with them all within one set of quotation marks and it only read the first line. How come what is so special about your use of quotation marks

Adjacent string literals are concatenated. So "Hello " "world" becomes "Hello world". Intervening whitespace (space, tab, newline, etc.) does not mess with this.

Originally Posted by NickHolmes

3) Finally I see that conname doesn't have a & infront of it Why? and if I want to have a name that is more than 1 character long how do I do it.

For a single character with %c you would use &conname. But for a string (%19s), you don't use &conname because an array name (conname) used in an expression decays into a pointer to the first element (&conname[0]). You don't want &conname for a string because the type is not correct.

Dear Dave,
You are a star. Thank you so very much.
One last question when I try to print out the

printf("\t%s",mycon[i].name);

it only ever prints out the first value regardless of what i is and then when I repeat the statement

ie printf("\t%s\t%s",mycon[i].name,mycon[i].name

does the program print out the first 2 values.

Also the first 2 values are null?

Is there a simple way of saving mycon[1].name as some string, then mycon[2].name as another string, with the same name but a [x] type variable.
I am sorry for being so thick. You have completely solve the read issues and things work great now.
Thanks again
Nick