Question

I have the following function

for(i = 0; i < lines; i++)
    fgets(i[*compare], 36, fp);

It populates the “pointer to an array of X chars of an array of X chars with the string from the file pointer stream fp. The variable lines is the number of lines the file has(precomputed).

I wish to calculate the reading speed of the fgets operation. However I am unsure of how to do this, nor the “formula”

Answer 1

Use clock_gettime to obtain some time, and wrap it around fgets. Then appropriately subtract a from b and you have the time it took to execute fgets (and one clock_gettime call).

#include <time.h>
struct timespec a, b;
clock_gettime(CLOCK_MONOTONIC, &a);
fgets(...)
clock_gettime(CLOCK_MONOTONIC, &b);

36 chars is not a lot, so it’ll be over faster than can be noticably measured. (But then again I hear Linus’s words (about git), “well maybe on Windows maybe you can [measure it]”…) Anyhow, you then now that (at most) this many chars were transferred in the found delta time.