scanf

This is a discussion on scanf within the C Programming forums, part of the General Programming Boards category; What does Code: int var; scanf("%*10d", &var); means? The * character and 10 number....

  1. #1
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    scanf

    What does

    Code:
    int var;
    scanf("%*10d", &var);
    means?

    The * character and 10 number.

  2. #2
    and the hat of wrongness Salem's Avatar
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    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    Im not preety sure what do they mean with "Suppresses assignment. The conversion that follows occurs as usual, but no pointer is used; the result of the conversion is simply discarded.".

    I mean what should i do in the following code below; when suppression is turned on? Should i just getchar() the next input field?

    If the next input field is a valid one for the called scanf, just ignore it if suppression is turned on?

    Code:
    int minscanf(char *fmt, ...)
    {
        va_list ap;
        char *p;
        int suppression;
        int field;
        
        union {
              int ival;
              short int sival;
        } val;
        
        va_start(ap, fmt);
        for(p = fmt; *p; p++) {
              while(*p == ' ' || *p == '\t')
                 p++;
              
              if(*p == '\0')
                 break;
                 
              suppression = field = 0;
              if(*p == '%') {
                    if(*++p == '\0')
                        break;
                    if(*p == '*') {
                       suppression = 1;
                       if(*++p == '\0')
                          break;
                    }
                    while(isdigit(*p) && *p) 
                       field = field * 10 + *p++ - '0';
              }
              if(suppression) {
                   
              }
        }
    }
    Last edited by Tool; 02-18-2010 at 12:48 PM.

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by MSDN
    An asterisk (*) following the percent sign suppresses assignment of the next input field, which is interpreted as a field of the specified type. The field is scanned but not stored.
    I interpret this as scanf actually reads the data in the field specifier but doesn't store the data in any variable.
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    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

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  5. #5
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    scanf:

    I want to add one more thing to the Elysia's answer.

    As he mentioned,* operator in the format specifier of scanf function is used to suppress the assignment of the input to a pointer.scanf won't include it in the count of successful assignments.

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