Wont run in X, works fine in alt+F1 terminal

This is a discussion on Wont run in X, works fine in alt+F1 terminal within the Linux Programming forums, part of the Platform Specific Boards category; i have this code to determine which lights are on, on a keyboard. but if i run it in x ...

  1. #1
    Registered User zmerlinz's Avatar
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    Wont run in X, works fine in alt+F1 terminal

    i have this code to determine which lights are on, on a keyboard.

    but if i run it in x windows it doesn't work, i get the error
    Code:
    ioctl: Invalid Argument
    but if i press ctrl+alt+f1 for example the code will work in one of these terminals fine.

    is there a way to get it to work in x windows, or is ioctl limited to terminals ??

    here is the code
    Code:
    #include <stdio.h>
    #include <fcntl.h>
    #include <sys/stat.h>
    #include <linux/kd.h>  /* Keyboard IOCTLs */
    #include <sys/ioctl.h> /* ioctl()         */
    #include <sys/types.h>
      
    #define ERROR -1
     
    void checkleds();
    long int arg;
    int main()
        {
           int fd;       /* Console fd (/dev/tty). Used as fd in ioctl() */
           //long int arg; /* Where the LED states will be put into.       */
     
              /* To use as the fd in ioctl(). */
              if ((fd = open("/dev/tty", O_NOCTTY)) == ERROR) {
                 perror("open");
                 exit(ERROR);
              }
              printf("first %d\n" , arg);
              /* Value stored in arg. */
              if (ioctl(fd, KDGETLED,&arg) == ERROR) {
                 perror("ioctl");
                 printf("%d\n", arg);
                 close(fd);
                 exit(ERROR);
              }
     
              /* Here we print out current LEDS. */
            checkleds();
        }
     
    void checkleds()
        {
            /* LED_SCR = 0x1, LED_NUM = 0x2, LED_CAP = 0x4 */
     
            if (arg == LED_SCR) printf("Scroll Lock LED is on.\n");
            else if (arg == LED_NUM) printf("Numeric Lock LED is on.\n");
            else if (arg == LED_CAP) printf("Caps Lock LED is on.\n");
     
            else if (arg == LED_NUM + LED_CAP)
               printf("Numeric Lock and Caps Lock LEDs are on.\n");
     
            else if (arg == LED_NUM + LED_SCR)
               printf("Numeric Lock and Scroll Lock LEDs are on.\n");
     
            else if (arg == LED_CAP + LED_SCR)
               printf("Caps Lock and Scroll Lock LEDs are on.\n");
     
            else if (arg == LED_NUM + LED_SCR + LED_CAP)
               printf("Numeric Lock, Scroll Lock, and Caps Lock LEDs are on.\n");
     
            else if (arg == 0)
              printf("No LEDs are on. \n");
     
            }
    thanks for any help in this matter
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  2. #2
    Registered User linuxdude's Avatar
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    I would think that X takes over the keyboard functions and does something else with them. You might have to go to another website. but to critique your code
    Code:
    1. First you need to include stdlib.h for exit and unistd.h for close
    2. You need %ld in your printf statements
    3. You need to return 0 in your main function

  3. #3
    Obsessed with C chrismiceli's Avatar
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    Did you try including <sys/kbio.h>, I think that is where KDGETLED is defined.
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  4. #4
    Registered User zmerlinz's Avatar
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    GETLED is defined in ioctl.h, i searched for kbio.h and it seems that it is used mainly for SPARC systems
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  5. #5
    Obsessed with C chrismiceli's Avatar
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    oh okay, It should work in X unelss X is doing something to restrict it. ioctl's communicate directly to the kernel and then to the device, X must be restricting that ioctl, don't know why or how, I will try and do mroe research on this topic.
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  6. #6
    Registered User zmerlinz's Avatar
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    thanks a lot, this is really baffling me as well
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