I am reading in data from a file orderedfile.txt. Sometimes this file has a header of the form:
BEGIN header
Real Lattice(A) Lattice parameters(A) Cell Angles
2.4675850 0.0000000 0.0000000 a = 2.467585 alpha = 90.000000
0.0000000 30.0000000 0.0000000 b = 30.000000 beta = 90.000000
0.0000000 0.0000000 30.0000000 c = 30.000000 gamma = 90.000000
1 ! nspins
25 300 300 ! fine FFT grid along <a,b,c>
END header: data is "<a b c> pot" in units of Hartrees
1 1 1 0.042580
1 1 2 0.049331
1 1 3 0.038605
1 1 4 0.049181
and sometimes no header is present and the data starts on the first line. My code for reading in the data is shown below. It works when the data starts on line one, but not with the header present. Is there a way to get around this?
int readinputfile() {
FILE *potential = fopen("orderedfile.txt", "r");
for (i=0; i<size; i++) {
fscanf(potential, "%lf %lf %*f %lf", &x[i], &y[i], &V[i]);
}
fclose(potential);
}
The following code will use fgets() to read each line. For each line sscanf() is used to scan the string and store it into double variables.
See a running example (with stdin) at ideone.
#include <stdio.h>
int main()
{
/* maybe the buffer must be greater */
char lineBuffer[256];
FILE *potential = fopen("orderedfile.txt", "r");
/* loop through every line */
while (fgets(lineBuffer, sizeof(lineBuffer), potential) != NULL)
{
double a, b, c;
/* if there are 3 items matched print them */
if (3 == sscanf(lineBuffer, "%lf %lf %*f %lf", &a, &b, &c))
{
printf("%f %f %f\n", a, b, c);
}
}
fclose(potential);
return 0;
}
It is working with the header you provided but if in the header a line such as:
1 1 2 0.049331
would appear then this line would also be read. Another possibility would be to search for the word END header if BEGIN header is present as it is in your given header or use a line count if the number of lines is known.
To search for sub strings the function strstr() could be used.
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