plot.c

/* plot.c - example of unix pipe. Calls gnuplot graph drawing package to draw
   graphs from within a C program. Info is piped to gnuplot */
/* Creates 2 pipes one will draw graphs of y=0.5 and y = random 0-1.0 */
/* the other graphs of y = sin (1/x) and y = sin x */
/*  c89 -o plot plot.c plotter.c  - ON DECS */
/*  acc -o plot plot.c plotter.c  - ON SUNS */

#include "externals.h"
#include <signal.h>

#define DEG_TO_RAD(x) (x*180/M_PI)

double drand48();
void quit();

FILE *fp1, *fp2, *fp3, *fp4, *fopen();

main()
{   float i;
    float y1,y2,y3,y4;

    /* open files which will store plot data */
    if ( ((fp1 = fopen("plot11.dat","w")) == NULL) ||
           ((fp2 = fopen("plot12.dat","w")) == NULL) ||
            ((fp3 = fopen("plot21.dat","w")) == NULL) ||
             ((fp4 = fopen("plot22.dat","w")) == NULL) )
              { printf("Error can't open one or more data files\n");
                exit(1);
              }
              
    signal(SIGINT,quit); /* trap ctrl-c call quit fn */
    StartPlot();
    y1 = 0.5;
    srand48(1); /* set seed */
    for (i=0;;i+=0.01) /* increment i forever use ctrl-c to quit prog */
      { y2 =  (float) drand48();
        if (i == 0.0)
           y3 = 0.0;
       else
           y3 = sin(DEG_TO_RAD(1.0/i));
        y4 = sin(DEG_TO_RAD(i));
        
        /* load files */
        fprintf(fp1,"%f %f\n",i,y1);
        fprintf(fp2,"%f %f\n",i,y2);
        fprintf(fp3,"%f %f\n",i,y3);
        fprintf(fp4,"%f %f\n",i,y4);
       
        /* make sure buffers flushed so that gnuplot reads up to data file */ 
        fflush(fp1);
        fflush(fp2);
        fflush(fp3);
        fflush(fp4);
        
        /* plot graph */
        PlotOne();
        usleep(250); /* sleep for short time */
      }
}

void quit()
{  printf("\nctrl-c caught:\n Shutting down pipes\n");
   StopPlot();
   
   printf("closing data files\n");
   fclose(fp1);
   fclose(fp2);
   fclose(fp3);
   fclose(fp4);
   
   printf("deleting data files\n");
   RemoveDat();
}