如何从 txt 文件中读取数据并忽略我不想要的值，直到达到某个阈值？

Question

I am tasked with reading data from a txt file that has values in 2 long columns. On the right side is a time and on the left side is a voltage level. an example of the txt file would look like this :

0.000000     -0.031960
0.000977      0.076080
0.001953      0.089640
0.002930      0.065460
0.003906      0.083060
0.004883     -0.074380
0.005859      0.092880
0.006836      0.027440
0.007812      0.058540
0.008789      0.026980
0.009766     -0.082800
0.010742      0.049660
0.011719      0.003560
0.012695      0.046220
0.013672      0.063120
0.014648      0.016040
0.015625      0.030760

I want to read this file and ignore all of the data until the I come across a voltage (right side) that is above 0.5. And then output values that meet another threshold from there until the file ends.

Ive started my code on reading the file but I just do not know how I would read the data and and output data only when the threshold is met.

This is what I have done so far:

#include <stdio.h>
#define MAXCHAR 1000

int main() {
 FILE *fp;
    char str[MAXCHAR];
    char* filename = "test1.txt";
 
    fp = fopen(filename, "r");
    if (fp == NULL){
        printf("Could not open file %s",filename);
        return 1;
    }
    while (fgets(str, MAXCHAR, fp) != NULL)
    if ()
        printf("%s", str);
    fclose(fp);
    return 0;
}

Answer 1

This may help. I change the value of the first threshold in this for testing (your dataset did not have any voltages over 0.5...)

#include <stdio.h>
#define MAXCHAR 1000

int main() {
    double thres_1 = 0.08;
    FILE *fp;
    char str[MAXCHAR];
    char* filename = "test1.txt";

    fp = fopen(filename, "r");
    if (fp == NULL){
        perror("Could not open file ");
        return 1;
    }
    int tmet = 0;
    while (fgets(str, MAXCHAR, fp) != NULL) {
        float t, v;
        if (sscanf(str, "%g%g", &t, &v) == 2) {
            if (v >= thres_1) {
                tmet = 1;
            }
            if (tmet) {
                printf("%f\t%f\n", t, v);
            }
        }
    }
    if (!tmet) {
        printf("Threshold was never exceeded");
    }
    fclose(fp);
    return 0;
}

The "second threshold", and what to do when it is met, wasn't really specified, but you can build more code to detect that and do something else inside the loop.

Answer 2

before this (not correct) statement;

if ()

the code needs to extract the two values from the current input line