help with struct

This is a discussion on help with struct within the C Programming forums, part of the General Programming Boards category; hello guys, i have been thinking of my college project work given to me. where in one sutitation i was ...

  1. #1
    Registered User ssharish2005's Avatar
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    help with struct

    hello guys,
    i have been thinking of my college project work given to me. where in one sutitation i was suppose to check where a structure is empty are not. for instance
    Code:
    struct something
    {
         int something1;
         int something2[20];
    };
    
    
    int main()
    {
           struct something some[10];
    
          if(how do i check that some[1] struct variable is empty)
    }
    is there any way that i can check that.

    i got one more thing to be clarified about strtok fucntion, lets take an example
    Code:
    #include <stdio.h>
    #include <string.h>
    
    int main()
    {
        char str[]= {"This is a test string"};
        char *p;
        
        p=strtok(str," ");
        while(p != NULL)
        {
            printf("Token : %s\n",p);
            p=strtok(NULL," "); 
        }
        printf("The original string \" %s \"",str);
        
        getchar();
        return 0;
    }
    /*my ouput
    Token : This
    Token : is
    Token : a
    Token : test
    Token : string
    The original string " This "
    */
    if u look at that code the first call to function strtok is with the orginal string 'str' and with the second call i am sending the update pointer NULL as a parameter. and at the end i wanted to print the original string of 'str'. but after using strtok my original string is changed which just contains the first word. is there any way that i can get back that string. well i thought of one way that's copy the original string to some other string before the sending the orginal string to strtok.

    well, it might me simple thing which might have confused me a lot, can any one explain this please

    ssharish2005
    Last edited by ssharish2005; 12-12-2005 at 06:40 PM.

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    if(how do i check that some[1] struct variable is empty)
    Check all members for zero (or whatever it was initialized to), and strings for "".
    dwk

    Seek and ye shall find. quaere et invenies.

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  3. #3
    cwr
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    When you declare a struct as an automatic variable (inside a function), it's filled with undefined values unless you initialise it. There's no such concept as "empty". Initialise the struct to some sentry values (perhaps 0), and use that to denote "empty".

    As for strtok, it will always put nulls into your string. Make a copy if you want it untouched.

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Code:
    p=strtok(str," ");
    That's not how you use strtok(). At least, I don't think it is.

    [edit]
    Yes it is; sorry. http://faq.cprogramming.com/cgi-bin/...&id=1044780608
    [/edit]
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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    Unofficial Wiki FAQ: cpwiki.sf.net

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    Projects: codeform, xuni, atlantis, nort, etc.

  5. #5
    Registered User ssharish2005's Avatar
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    well, the best way that i can keep original string safe is just have a copy of it. as crw says.

    ssharish2005

  6. #6
    Just Lurking Dave_Sinkula's Avatar
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    To keep the original string unmodified, consider using strcspn or sscanf instead of using strtok.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  7. #7
    Registered User ssharish2005's Avatar
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    thax very my DAVE is got sorted

    ssharish2005

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