Thread: Standard bioskey function

  1. #1
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    Standard bioskey function

    Hi,

    I have faced the following code, can you help me to write a standard version of it:

    Code:
    struct timeval tv;
    
    int bioskey() {
        fd_set readfds;
    
    
        FD_ZERO (&readfds);
        FD_SET (fileno(stdin), &readfds);
        tv.tv_sec=0; tv.tv_usec=0;
        select(16, &readfds, 0, 0, &tv);
    
    
        return (FD_ISSET(fileno(stdin), &readfds));
    }
    I get:

    Code:
    error: call to undeclared function 'fileno';

  2. #2
    Registered User rstanley's Avatar
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    Did you "#include <stdio.h>" that declares the function, fileno().
    Last edited by rstanley; 02-03-2024 at 11:34 AM.

  3. #3
    and the hat of int overfl Salem's Avatar
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    You should also read the manual page for select() while you're at it.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  4. #4
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    I found this from stackoverflow:

    Code:
    int bioskey(void)
    {
        //struct timeval tv = { 0L, 0L };
        fd_set fds;
        FD_ZERO(&fds);
        FD_SET(0, &fds);
        return select(1, &fds, NULL, NULL, &tv) > 0;
    }

  5. #5
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    Depending on your system you may also need to define _POSIX_C_SOURCE before including stdio.h to use fileno:
    Code:
    #define _POSIX_C_SOURCE
    #include <stdio.h>
    A little inaccuracy saves tons of explanation. - H.H. Munro

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