/*
 * plot.c
 * Build: gcc -lm -oplot plot.c
 * Usage: just run :-) ^C to terminate.
 */

#include <stdio.h>
#include <math.h>
#include <unistd.h>

void update_data(FILE* f) {
    static double phase = 0.;
    double t;
    for (t = 0.; t < 10.; t += 0.1)
        fprintf(f, "%f %f\n", t, sin(t + phase));
    phase += 0.1;
}

int main(void) {
    FILE* cmdpipe = popen("gnuplot -", "w");
    for (;;) {
        FILE* datafile = fopen("plot.dat", "w");
        update_data(datafile);
        fclose(datafile);
        
        fputs("plot 'plot.dat' with lines\n", cmdpipe);
        fflush(cmdpipe);
        usleep(100 * 1000); /* Wait for 0.1s */
    }
}