[SOLVED] RTT: string padding does not work

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  • [SOLVED] RTT: string padding does not work

    I'm trying to use the segger RTT SEGGER_RTT_vprintf to print a string with padding.

    The following code doesn't seem to work properly

    C Source Code

    1. SEGGER_RTT_vprintf(0, "%d %-10s - %s", 10, "TEST", "module");

    The padding behaviour doesn't work as mentioned in the documentation.

    Expected10 TEST - module
    Actual10 TEST - module



    When looking at the code, in "%s" mode, the FieldWith seems ignored

    C Source Code

    1. case 's':
    2. {
    3. const char * s = va_arg(*pParamList, const char *);
    4. do {
    5. c = *s;
    6. s++;
    7. if (c == '\0') {
    8. break;
    9. }
    10. _StoreChar(&BufferDesc, c);
    11. } while (BufferDesc.ReturnValue >= 0);
    12. }
    13. break;
    Display All

    RTT version: 7.84d


    Best,
    Gabriel

  • Hi Gabriel,
    this is intentional.

    SEGGER_RTT_printf() is (by far) not a complete printf() implementation.
    Flags, FieldWidth and Precision will be ignored for specifiers s & c.

    Unfortunately, this information was missing from the API documentation in the Wiki.
    We just added this information to prevent confusion:
    wiki.segger.com/RTT#SEGGER_RTT_printf.28.29

    For your specific use case, I would suggest to use snprintf() or similar,
    provided by the library of your choice.

    BR
    Fabian
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