Thread: Help with printf formatting

  1. #1
    Registered User
    Join Date
    Apr 2009

    Help with printf formatting

    Hi guys, first time posting.
    I was reading over some code and I need help identifying what the following snippet means:

    char ack_buf [599];
    printf("\033[2K\r%s\n", ack_buf);
    I don't understand what the "\033[2k" does. I've tried googling for quite a while but all the explanations pertaining to these characters seemed irrelevant and did not make sense to me.

  2. #2
    Registered User
    Join Date
    Apr 2008
    These are escape sequences interpreted by the terminal. Those sequences allow to move the cursor, change colors, clear the screen, etc. Google 'terminal escape sequence' and you will get your answer for the meaning of 2K in particular. Notice this has nothing to do with C programming.

  3. #3
    Frequently Quite Prolix dwks's Avatar
    Join Date
    Apr 2005
    See for example

    It looks like "ESC [ 2 K" clears the entire line, as if you'd positioned the cursor at the beginning of the line and overwritten it with all spaces.
    Last edited by dwks; 04-07-2009 at 12:54 PM.

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  4. #4
    Registered User
    Join Date
    Apr 2009
    Ah thank you very much! I will go look that up immediately. I apologize for my inexperience; I was not aware of these terminal escape sequences.

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