Thread: problem getting structure to work in my function

Hello folks,

I hope my question is not wasting anyones time here. I was trying to make a program that will assist me in my daily work, the idea being to automatically generate a file that contains some inforamation about products and so forth.


I decided to put this information into a structure and then create a file and read the contents of struct to it.

I can get the program to work when I do not use a seperate function, but i cannot seem to get the program to work while having a seperate function. My knowledge of passing structures seems to be a bit limited.

here is the function:

Code:

void createFile(char pc, struct CALL){
FILE *nf;

     nf = fopen(pc, "w");

     if (nf == NULL) {
     fprintf("Can't open created file %s!\n", pc);
     exit(1);
     }

   if (nf != NULL) {
    fwrite(&c, 1, sizeof(CALL), nf);
    fclose(nf);
    }

}

function prototype:

Code:

void createFile(char filename, struct CALL);

and the call to the function:

Code:

createFile(pc,c);

I really tried lots of different attempts and looked at many websites and resource but i still get the same problems. Can someone point out where I went wrong...sure there are numerous errors.


Anyway this is the program that works without function(so you know that i am trying )

Code:

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<string.h>

char *genCallNr();
//void createFile(char *callnr);

struct CALL {
   int qty;
   char contract[5], owner[5], partnr[6], date1[14], date2[14];
   char *callnr;
};

int main(void)
{
 struct CALL c;

 strcpy(c.contract, "DELL");
 strcpy(c.owner, "EMEA");
 strcpy(c.partnr, "615TW");
 strcpy(c.date1, "030320091148");
 strcpy(c.date2, "030320091148");
 c.callnr = genCallNr();
 printf("\n%s", c.callnr);

free (c.callnr);

printf("\n%s\t%s\t%s\t%s\n", c.contract, c.owner, c.partnr, c.callnr);
//createFile(c.callnr);
int i;
FILE *nf;
char *pc;
char cn[12];
pc = cn;

pc = genCallNr();

printf("\n%s", pc);

 nf = fopen(pc, "w");

     if (nf == NULL) {
     fprintf("Can't open created file %s!\n", pc);
     exit(1);
     }

   if (nf != NULL)
fwrite(&c, 1, sizeof(struct CALL), nf);

    fclose(nf);



}

char *genCallNr(){

char *callnr = malloc(12);
time_t now;

 struct tm *ts;
 char buf[12];

 now = time(NULL);
 ts = localtime(&now);

 strftime(buf, sizeof(buf), "1%y%m%d%H%M", ts);
 //printf("\n%s", buf);
 strncpy(callnr, buf,12);
// printf("\n%s", callnr);

return callnr;


}

/*
void createFile(char *callnr){
FILE *nf;

     nf = fopen(callnr, "w");

     if (nf == NULL) {
     fprintf("Can't open created file %s!\n", callnr);
     exit(1);
     }

   if (nf != NULL) {
    fwrite(callnr, 1, sizeof(callnr), nf);
    fclose(nf);
    }

}

*/

there are problems with the information that is writen into the file by the above program but i will tackle them when the problem with the function is resolved...

You mean in my function prototype and function have : struct CALL c instead of struct call:

Code:

void createFile(char filename, struct CALL c);

is the function call :

Code:

 
createFile(pc,c);

that ok?

In your function, you're passing in a copy of the struct, and the function changes the copy, not the original where the function call happens. Your function needs to take a CALL* and operate on that, and when you call the function pass in the address of c (&c).

struct_callsFUNC.c: In function \u2018main\u2019:
struct_callsFUNC.c:56: warning: passing argument 1 of \u2018createFile\u2019 makes integer from pointer without a cast
struct_callsFUNC.c:56: error: type of formal parameter 2 is incomplete


line 56 is:

Code:

createFile(pc,c);

function and prototype looks like this:

Code:

void createFile(char filename, struct CALL c);

with the structure looking like this:

Code:

struct CALL {
   int qty;
   char contract[5], owner[5], partnr[6], date1[14], date2[14];
   char *callnr;
};


int main(void){

 struct CALL c;

...

also I get an error here, when trying to write to the file:

Code:

   if (nf != NULL) {
    fwrite(&c, 1, sizeof(CALL), nf);
    fclose(nf);
    }

when trying to read the structure to the file
struct_callsFUNC.c:92: error: \u2018CALL\u2019 undeclared (first use in this function)
struct_callsFUNC.c:92: error: (Each undeclared identifier is reported only once
struct_callsFUNC.c:92: error: for each function it appears in.)

You only know "struct call". Use

Code:

typedef struct CALL { ... } CALL;

EDIT: You were faster

a quick update with the errors I am having problem solving:

qa@qa:~/Programming$ gcc -o struct_callsFUNC struct_callsFUNC.c
struct_callsFUNC.c:7: warning: \u2018struct CALL\u2019 declared inside parameter list
struct_callsFUNC.c:7: warning: its scope is only this definition or declaration, which is probably not what you want
struct_callsFUNC.c: In function \u2018main\u2019:
struct_callsFUNC.c:55: error: type of formal parameter 2 is incomplete
struct_callsFUNC.c: At top level:
struct_callsFUNC.c:80: error: conflicting types for \u2018createFile\u2019
struct_callsFUNC.c:7: error: previous declaration of \u2018createFile\u2019 was here
struct_callsFUNC.c: In function \u2018createFile\u2019:
struct_callsFUNC.c:86: warning: passing argument 1 of \u2018fprintf\u2019 from incompatible pointer type

and here is the code:

Code:

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<string.h>

char *genCallNr();
void createFile(const char *Ppc, struct CALL c);

struct CALL {
   int qty;
   char contract[5], owner[5], partnr[6], date1[14], date2[14];
   char *callnr;
}CALL;


int main(void){

 struct CALL c;

 strcpy(c.contract, "DELL");
 strcpy(c.owner, "EMEA");
 strcpy(c.partnr, "615TW");
 strcpy(c.date1, "030320091148");
 strcpy(c.date2, "030320091148");
 c.callnr = genCallNr();
 printf("\n%s", c.callnr);

free (c.callnr);

printf("\n%s\t%s\t%s\t%s\n", c.contract, c.owner, c.partnr, c.callnr);
//createFile(c.callnr);
char *pc;
char cn[12];
pc = cn;

pc = genCallNr();
char *Ppc ;
Ppc = pc;
printf("\n%s", Ppc);

createFile(pc, c);

}

char *genCallNr(){

char *callnr = malloc(12);
time_t now;

 struct tm *ts;
 char buf[12];

 now = time(NULL);
 ts = localtime(&now);

 strftime(buf, sizeof(buf), "1%y%m%d%H%M", ts);
 //printf("\n%s", buf);
 strncpy(callnr, buf,12);
// printf("\n%s", callnr);

return callnr;

}


void createFile(const char *Ppc, struct CALL c){
FILE *nf;

     nf = fopen(Ppc, "w");

     if (nf == NULL) {
     fprintf("Can't open created file %s!\n", Ppc);
     exit(1);
     }

   if (nf != NULL) {
    fwrite(&c, 1, sizeof(CALL), nf);
    fclose(nf);
    }

}

maybe I misunderstood both of your comments?

I am blind!

sorry matsp, i completely missed that and thanks also MK27 and Brafil

Everything works now. I have learnt my lesson the declare the function prototypes AFTER the structure if they are calling them...

When I run the program I get this:

^@^@^@^@DELL^@EMEA^@615TW^@030320091148^@K03032009 1148^@^H^H^D^H

Why is this?