CODEWITHSUNDEEP
c++printfoutput
Gerard Júlio
Gerard Júlio

Reputation: 55

Printf Fprintf outputorder

I don't get why "cout" outputs after the file is written, it makes no sense to me... How would I do it correctly? I tried with sleep between the two, but it's still not reversing the order like I want to.

  cout << "Writing to file";
  fp = fopen("plume_visualisation.txt","w");
  for(int i=0;i<grid;i++)
    for(int j=0;j<grid;j++)
      for(int k=0;k<grid;k++)
    fprintf(fp,"%f\t%f\t%f\t%f\n",x[i],y[j],z[k],suv[i][j][k]);
  fclose(fp);

Upvotes: 3

Views: 82

Answers (1)

AmphotericLewisAcid
AmphotericLewisAcid

Reputation: 2299

C++ writes to the output stream, stored in a buffer. You need to flush the buffer to write it to the console. Remember how you probably learned to write a line to the console?

std::cout << "This is a message" << std::endl;

What std::endl does is place a newline character at the end of the message, and flush the buffer. Based on your code, I'm guessing you thought "Hey, I can just leave off endl and it won't write a new line." This is a good way to think...but you probably didn't realize that endl also flushes the buffer. This is what you want:

std::cout << "Writing to file" << std::flush;

Also notice how I prefixed cout and flush with "std." Using "using namespace standard" is bad practice that you should avoid.

On a related note, you're already using C++. Instead of doing file IO the old C way of fprintf, instead set up a file stream. It works pretty much the same way that console IO does. Here's a great guide on how to do what you're doing in a more idiomatic fashion: http://www.cplusplus.com/doc/tutorial/files/

Upvotes: 5

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