在c中调用gnuplot

在c里面调用gnuplot，可以直接把图形输出到文件：

# surface.c
#include
/*
        Author: Ioan Vancea (www.vioan.ro)
        *****************************/
int main()
{
        FILE *pipe = popen("gnuplot -persist","w");
        fprintf(pipe, "set samples 40\n");
        fprintf(pipe, "set isosamples 40\n");
        fprintf(pipe, "set hidden3d\n");
        fprintf(pipe, "set xrange [-8.000:8.000]\n");
        fprintf(pipe, "set yrange [-8.000:8.000]\n");
        fprintf(pipe, "set zrange [-2.000:2.000]\n");
        fprintf(pipe, "set terminal png\n");
        fprintf(pipe, "set output 'graph.png'\n");
        fprintf(pipe, "set title 'We are plotting from C'\n");
        fprintf(pipe, "set xlabel 'Label X'\n");
        fprintf(pipe, "set ylabel 'Label Y'\n");
        /* fprintf(pipe, "plot 'datafile.dat' using 1:2\n");*/
        fprintf(pipe, "splot cos(x)+cos(y)\n");

  close(pipe);
  return 0;
}

也可以动态显示图形：

# popen.c

#include 
#include 
#include 
#include 
#include 
#include 

#define PANIC(a) do { \
                perror(a); \
                if (temp_name) unlink(temp_name);\
                exit(1);\
        } while(0)

int main() {
    FILE *command,*data;
    char *temp_name;
    double a,b;
    int i;

    if ((temp_name = tmpnam((char *) 0)) == 0) PANIC("tmpnam failed");
    if(mkfifo(temp_name, S_IRUSR | S_IWUSR) != 0) PANIC("mkfifo failed");
    command = popen("gnuplot","w");
    fprintf(command,"plot \"%s\" with lines\n",temp_name); fflush(command);
    data = fopen(temp_name,"w");
    for (i=0; i<20; i++) {
        a = i/10.0;
        b = sin(a);
        fprintf(data,"%f %f\n",a,b);
    }
    fclose(data);
    fprintf(stderr,"press enter to continue..."); fflush(stderr);
    getchar();

    fprintf(command,"plot \"%s\" with lines\n",temp_name); fflush(command);
    data = fopen(temp_name,"w");
    for (i=0; i<20; i++) {
        a = i/10.0;
        b = cos(a);
        fprintf(data,"%f %f\n",a,b);
    }
    fclose(data);
    fprintf(stderr,"press enter to continue..."); fflush(stderr);
    getchar();
    fclose(command);
    unlink(temp_name);
    return 0;
}