#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    pid_t pid;
    int pfd[2];
    int i, status;
    FILE * sd;
    int x[]= {20,275,240,5,20,45,170,205,240,5,20,60,60,70,70,70,65,75,70,70,95,95};
    int y[]= {50,50,25,25,25,12,12,25,25,25,50,50,70,70,85,80,80,80,80,70,70,50};
    
    /*
     * Create a pipe.
     */
    if (pipe(pfd) < 0) {
        perror("pipe");
        exit(1);
    }

    /*
     * Create a child process.
     */
    if ((pid = fork()) < 0) {
        perror("fork");
        exit(1);
    }

    /*
     * The child process executes "matlab" with -nodesktop option.
     */
    if (pid == 0) {
        /*
         * Attach standard input of this child process to read from the pipe.
         */
        dup2(pfd[0], 0);
        close(pfd[1]);  /* close the write end of the pipe */

        execlp("scilab", "scilab", "-nw", 0);
        perror("exec");
        exit(-1);
    }

    /*
     * We won't be reading from the pipe.
     */
    close(pfd[0]);
    sd = fdopen(pfd[1], "w");  /* to use fprintf instead of just write */
    fprintf(sd, "x= [");
    for ( i= 0; i<22; i++)
      fprintf(sd, "%d ", x[i]);
    fprintf(sd, "];\n");
    fprintf(sd, "y= [");
    for ( i= 0; i<22; i++)
      fprintf(sd, "%d ", y[i]);  /* other data could be sent here */
    fprintf(sd, "];\n");fflush(sd);
    fprintf(sd, "subplot(2,1,1);\n");
    fprintf(sd, "plot2d(x,y);\n");
    fprintf(sd, "subplot(2,1,2);\n");
    fprintf(sd, "plot2d(y,x);\n"); fflush(sd);
    sleep(5);
    fprintf(sd, "subplot(2,1,1);\n");
    fprintf(sd, "plot(x);\n");
    fprintf(sd, "subplot(2,1,2);\n");
    fprintf(sd, "plot(abs(fft(x,-1)));\n");fflush(sd);
    sleep(10);
    fprintf(sd, "\n exit\n"); fflush(sd);
    
    /* Wait for the child to exit and
     * close de pipe.
     */
    waitpid(pid, &status, 0);
    fclose(sd);

    /*
     * Exit with a status of 0, indicating that
     * everything went fine.
     */
    exit(0);
}