problem with arrays

when I print out my array in one place it works fine, in another function the same code don't work.

my code

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include "lab41.h"

int readfil(FILE *filen, person *personer[10]) {
    int counter = 0;
    char mystring[100];
    person p1;

    while(feof(filen) == NULL) {

                        fscanf(filen,"%s", &p1.fnamn);
                        fscanf(filen,"%s", &p1.enamn);
                                    fscanf(filen,"%d", &p1.alder);
                                    fscanf(filen,"%d", &p1.vikt);
                                    personer[counter] = &p1;
                                   
                                    /*--------test ---------*/
                                   
                        printf("%s", personer[counter]->fnamn);
                        printf("\n");
                        printf("%s", personer[counter]->enamn);
                        printf("\n");
                        printf("%d", personer[counter]->alder);
                        printf("\n");
                        printf("%d", personer[counter]->vikt);
                        printf("\n");
                       
                        /*--------slut test-------*/
                      counter++;
                      }
                printf("\n-----------------END---------------\n");
    return 0;
    }


int skriv_ut_personer(FILE *filen, person *personer[10]) {
int counter = 0;
rewind (filen);
        while(counter < (sizeof(personer)-1)) {
                        printf("%s", personer[counter]->fnamn);
                        printf("\n");
                        printf("%s", personer[counter]->enamn);
                        printf("\n");
                        printf("%d", personer[counter]->alder);
                        printf("\n");
                        printf("%d", personer[counter]->vikt);
                        printf("\n");
                counter++;
        }
 free(personer);

return 0;
}


int main() {
person *personer[10];
FILE *filen;
char filnamn[40];
enum filtyp {db,txt,bin};
typedef enum filtyp filtyp;

printf("Skriv filnamn: ");
scanf("%s", &filnamn);
if((filen = fopen(filnamn, "r")) == NULL) {
            printf("file don't exist");
            exit(1);
        }
readfil(filen,personer);
skriv_ut_personer(filen,personer);
return 0;
}

---

header

Code:

---

typedef struct {
        char fnamn[40];
        char enamn[40];
        int alder;
        int vikt;
        } person;

---

output

Code:

---

client128-24:CORSAIR $ ./a.out
Skriv filnamn: p.txt
Johan
olsson
32
64
nilj
kall
31
56
frida
........
32
12
monika
ulv
54
123
monika
ulv
54
123

-----------------END---------------
moni????
???W????1???1?X???????8?1??1??
-1607342536
0

???W????1???1?X???????8?1??1??
-1607342536
0

???W????1???1?X???????8?1??1??
-1607342536
0
a.out(607) malloc: *** error for object 0xbffff904: Non-aligned pointer being freed
*** set a breakpoint in malloc_error_break to debug

---

Quote:

---

while(feof(filen) == NULL)

---

do not use feof to control loop - read FAQ
--------------
also read description of the function you are using, feof never returns NULL, it returns true or false
----------------

Quote:

---

personer[counter] = &p1;

---

you are storing pointer to the local variable which will be
1. overwritten on the next loop iteration
2. destructed as soon as you leave the function

allright, I change personer[10] to a global varible and that it only print one post. but still the same.

output.

Code:

---

client128-24:CORSAIR $ ./a.out
enter filename:: p.txt
Johan olsson
32
64

-----------------END---------------
Joha???? ???W????1???1?????????8?1??1??
-1607342536
0
client128-24:CORSAIR

---

code

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include "lab41.h"
person *personer[10];

int readfil(FILE *filen) {
    int counter = 0;
    char mystring[100];
    person p1;

    while(counter < 1) {

                        fscanf(filen,"%s", &p1.fnamn);
                        fscanf(filen,"%s", &p1.enamn);
                                    fscanf(filen,"%d", &p1.alder);
                                    fscanf(filen,"%d", &p1.vikt);
                                    personer[counter] = &p1;
                                   
                                    /*--------test ---------*/
                                   
                        printf("%s", personer[counter]->fnamn);
                        printf(" ");
                        printf("%s", personer[counter]->enamn);
                        printf("\n");
                        printf("%d", personer[counter]->alder);
                        printf("\n");
                        printf("%d", personer[counter]->vikt);
                        printf("\n");
                       
                        /*--------slut test-------*/
                      counter++;
                      }
                         
                printf("\n-----------------END---------------\n");
    return 0;
    }


int skriv_ut_personer(FILE *filen) {
int counter = 0;
rewind (filen);
        while(counter < 1) {
                        printf("%s", personer[counter]->fnamn);
                        printf(" ");
                        printf("%s", personer[counter]->enamn);
                        printf("\n");
                        printf("%d", personer[counter]->alder);
                        printf("\n");
                        printf("%d", personer[counter]->vikt);
                        printf("\n");
                counter++;
        }
 

return 0;
}


int main() {
FILE *filen;
char filnamn[40];
enum filtyp {db,txt,bin};
typedef enum filtyp filtyp;

printf("enter filename: ");
scanf("%s", &filnamn);
if((filen = fopen(filnamn, "r")) == NULL) {
            printf("file don't exist");
            exit(1);
        }
readfil(filen);
skriv_ut_personer(filen);
return 0;
}

---

The problem isn't personer, it is with the fact that p1 is a local variable that gets destroyed and has it's memory reused for other purposes once the function that reads the file is finished.

You either need to allocate memory for person in the function that does the reading, and store that in the personer array, or make personer array not a pointer, but a array of class person.

--
Mats

allright. I'm trying to allocate memory with malloc but i'm getting a error.

&p1 = (person*) malloc(sizeof(person));

error: invalid lvalue in assignment

Yes, I can see that. You need to make p1 a pointer. You can't set the address of a variable, so &p1 or something like that can not be the left-hand side of = (which is pretty much what "lvalue" means - I mean, something that can go to the left of =).

Edit: And you should not cast the result of malloc. If you find that you get compiler errors from that, you are probably using a C++ compiler rather than a C compiler.

--
Mats

Now p1 is a pointer. now i get back to a old problem (p1 was a pointer before) now i get Segmentation Fault at

Quote:

---

fscanf(filen,"%s", p1->alder);

---

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include "lab41.h"
person *personer[10];


int readfil(FILE *filen) {
    int counter = 0;
    char mystring[100];
    person *p1;

    while(counter < 1) {
                                p1 = malloc(sizeof(person));
                                fscanf(filen,"%s", p1->fnamn);
                    fscanf(filen,"%s", p1->enamn);
                            fscanf(filen,"%s", p1->alder);
                            fscanf(filen,"%s", p1->vikt);
                            personer[counter] = p1;
                                   
                                    /*--------test ---------*/
                                   
                        printf("%s", personer[counter]->fnamn);
                        printf(" ");
                        printf("%s", personer[counter]->enamn);
                        printf("\n");
                        printf("%d", personer[counter]->alder);
                        printf("\n");
                        printf("%d", personer[counter]->vikt);
                        printf("\n");
                       
                        /*--------slut test-------*/
                      counter++;
                      }
                printf("\n-----------------END---------------\n");
    return 0;
    }


int skriv_ut_personer(FILE *filen) {
int counter = 0;
rewind (filen);
        while(counter < 1) {
                        printf("%s", personer[counter]->fnamn);
                        printf(" ");
                        printf("%s", personer[counter]->enamn);
                        printf("\n");
                        printf("%d", personer[counter]->alder);
                        printf("\n");
                        printf("%d", personer[counter]->vikt);
                        printf("\n");
                counter++;
        }
 

return 0;
}


int main() {
FILE *filen;
char filnamn[40];
enum filtyp {db,txt,bin};
typedef enum filtyp filtyp;
printf("Skriv filnamn: ");
scanf("%s", &filnamn);
if((filen = fopen(filnamn, "r")) == NULL) {
            printf("file don't exist");
            exit(1);
        }
readfil(filen);
skriv_ut_personer(filen);
return 0;
}

---

Code:

---

fscanf(filen,"%s", p1->alder);

---

I thought alder was an int? Why are you trying to read a string into it? (And you need & to read into an int variable as well.)

It's printing correct now. Thanks! but when it reach return 0 in main() the window close, should it do that? I use DeV-C++

Do something at the end of the program that stops it from closing? Perhaps read something from the console?

--
Mats