first time using C

This is a discussion on first time using C within the C Programming forums, part of the General Programming Boards category; Usually I use C++ but was recently given an assignment in C... here's the assignment: Declare a structure named Person. ...

  1. #1
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    first time using C

    Usually I use C++ but was recently given an assignment in C...
    here's the assignment:
    Declare a structure named Person. The Person structure should have the following fields:

    • char name[100];
    • int age;
    • float gpa;


    Write a function with the following signature:
    void fill_person(struct Person* per)
    Use printf to prompt the user for a name, age, and gpa. For input use fgets for the name and scanf for the age and gpa. The values should be stored in the structure pointed to by per.
    Write a second function with the following signature:
    void show_person(struct Person* per)
    This function should use printf to print out each of the members of the structure pointed to by per.
    Your main function needs only three lines:

    1. Create a struct person object
    2. Call the fill_person function
    3. Call the show_person function


    I've started my code but I can not get it to compile, can any one help?
    Here's my code:
    Code:
      1 #include<stdio.h>
    Code:
      2 struct Person
      3 {
      4     char name[100];
      5     int age;
      6     float gpa;
      7 
      8 };
      9     void fill_person(struct Person* per)
     10     {
     11       printf("Enter name of student:");
     12       fgets("%c",100, per->name);
     13       printf("Enter age of student:");
     14       scanf("%d", per->age);
     15       printf("Enter GPA of student:");
     16       scanf("%f", per->gpa);
     17 
     18     }
     19     void show_person(struct Person* per)
     20    {
     21       fgets("%c",100, per->name);
     22       printf("%d", per->age);
     23       printf("%f", per->gpa);
     24    }
     25 
     26 
     27 
     28 int main()
     29 {
     30 }


    here is the error I'm recieving:
    Code:
    assignment12.c: In function 'fill_person':
    Code:
    assignment12.c:12: warning: passing argument 3 of 'fgets' from incompatible pointer type
    /usr/include/stdio.h:604: note: expected 'struct FILE * __restrict__' but argument is of type 'char *'
    assignment12.c: In function 'show_person':
    assignment12.c:21: warning: passing argument 3 of 'fgets' from incompatible pointer type
    /usr/include/stdio.h:604: note: expected 'struct FILE * __restrict__' but argument is of type 'char *'




  2. #2
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    Did you really forget to call the functions you made?

    And int main() should return 0

  3. #3
    Registered User camel-man's Avatar
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    Code:
    printf("Enter name of student:");
     12       fgets("%c",100, per->name);
     13       printf("Enter age of student:");
     14       scanf("%d", per->age);
     15       printf("Enter GPA of student:");
     16       scanf("%f", per->gpa);
    When scanning for a name you need to use %s not %c(which is just one single character).
    Your scanf statments need an '&' before the variable you are trying to store the information in.
    ex)
    Code:
    scanf("%f", &per->gpa);

  4. #4
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    Thank you Camel-man.
    After fixing those issues I am still getting this error, I've looked into fgets and from what I understand it has to pass 3 arguments
    Code:
    assignment12.c: In function 'fill_person':
    assignment12.c:12: warning: passing argument 3 of 'fgets' from incompatible pointer type
    /usr/include/stdio.h:604: note: expected 'struct FILE * __restrict__' but argument is of type 'char (*)[100]'
    assignment12.c: In function 'show_person':
    assignment12.c:21: warning: passing argument 3 of 'fgets' from incompatible pointer type
    /usr/include/stdio.h:604: note: expected 'struct FILE * __restrict__' but argument is of type 'char *'
    I don't understand why I'm getting this error..

  5. #5
    Registered User camel-man's Avatar
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    char *fgets(char *s, int n, FILE *stream);
    That is fgets prototype.
    What you have is fgets("%c",100, per->name); I take it you are typing in the name from the command line, in that case you want to replace per->name with the file stream stdin which is your keyboard. fgets(per->name,100, stdin);

  6. #6
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    Thank you camel-man.
    Now should my struct be in my main?
    I was going to have my main be like this:
    Code:
    int main()
    {
    struct Person* per;
    fill_person(&per);
    show_person(&per);
    }

  7. #7
    Registered User camel-man's Avatar
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    Yes your struct should be in main, however you are creating a struct Person pointer, therefore when you call your function you do not need to use the '&'.
    Code:
    fill_person(&per);
    show_person(&per);
    should be
    Code:
    fill_person(per);
    show_person(per);

  8. #8
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    I got my code to compile, but now when I run it, It prompts me to enter the students name, and when I do that, and press enter I get
    "segmentation fault"
    and the program ends...

  9. #9
    Registered User camel-man's Avatar
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    Right, I did not notice that you are using an invalid pointer. You create your struct Person pointer yet you do not point it to a valid memory address. Have you used malloc before? You can either use malloc or create a local variable in main and point per to that location.

  10. #10
    Registered User hk_mp5kpdw's Avatar
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    You should not be using a pointer to the struct in main. You are instructed to create an object of type struct person in main, an actual object and not a pointer to one. As you pass this object to the two functions you are calling, you will need to use the address-of operator to get the object's address.

    [edit]Never mind, looks like you have another post that seems to address everything I mentioned here. Oh well.[/edit]
    Last edited by hk_mp5kpdw; 11-07-2012 at 05:57 AM.
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
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