CODEWITHSUNDEEP
cexportgnuplot
fragon
fragon

Reputation: 3471

How to export the data to .txt readable by GNUplot

Yesterday I was too tired to post correct and specific question. So there it is:

if (t==2){
    printf ("abc\n");
    printf ("abc = "); scanf ("%f",&r);
    printf ("abc = "); scanf ("%d",&n);
    printf ("abc = "); scanf ("%d",&k);
    a=2*r;
    b=2*r;
    c=2*r;

    for (i=0;i<=n;i++){
        float x=(float)rand()/((float)RAND_MAX/a);
        float y=(float)rand()/((float)RAND_MAX/b);
        float z=(float)rand()/((float)RAND_MAX/c);

        if ((x-(r))*(x-(r))+(y-(r))*(y-(r))+(z-(r))*(z-(r))<=(r*r))
            m++;

            if ( i % k ==0 && i > 0 ){
                freopen ( "data.txt","w", stdout );
                printf("%s %s      %s \n","#","n","Vka");
                Vka = ( 2*r*2*r*2*r )*m/i;
                printf("% 6.2f % 6.2f \n",n,Vka);
                fclose (stdout);
            }

    }

    Vk=(2*r*2*r*2*r)*m/n;
    printf ("abc =%d\n", m);
    printf ("abc=%d\n", n);
    printf("abc =%f", Vk);

    }

Unfortunately program does not work as I want it to work. It should export the data to the file "data.txt", but the file still looks like this: 

# n      Vka 
0.00   0.00

Morover the program finishes operation just after creating this file, while I want it to finish its operation on printing Vk in the terminal.

Upvotes: 0

Views: 460

Answers (2)

nibot
nibot

Reputation: 14928

  1. open the file before the loop
  2. write to the file inside the loop using fprintf
  3. close the file after the loop

There's no reason in this program to mess with stdout at all.

Upvotes: 1

askmish
askmish

Reputation: 6684

Use open() syscall to open the file write.txt and assign it to a fd, say fdout. Then use dup2(fdout, 1) for stdout.

You have 3 open pre-def file descriptors by default, in your OS, before you even reach main:
0 assigned to stdin, 1 to stdout, 2 to stderr.

From the manpage of dup2:

dup2(int oldfd, int newfd) makes newfd to be the copy of oldfd, closing newfd first if necessary.

The dup2 call replaces stdout with your open file write.txt. So when you printf the data to stdout, it will be written to your files rather than to the pre-defined fd's setup by the OS.

This will not only get your job done, the opening and closing of stdout is not your headache anymore.

Upvotes: 0

Related Questions