Runtime error

si im building a little program for revision

which is the folowing

Code:

---

#include <stdio.h>

typedef struct inventory{
        char partname[40];
        int partnumber;
        float price;
        int stock;
       
}Inventory;

void fill(FILE *main_program);
void get_info(Inventory *slot);

int main (void)
{
        int option=0;
        FILE *main;

        main=fopen("parts.txt","ab");

        printf("PLEASE select from the following options\n");
        printf("1. Enter new part\n");
        printf("2. Edit existing part\n");
        printf("3. Sort part list by number and write output file\n");
        printf("5 Quit\n\n");

        scanf("%d",&option);

        while(option!=5)
        {
                switch(option)
                {
                case 1:
                        fill(main);
                        break;

                }/*close switch*/

        }/*close while*/

        fclose(main);

        return 0;

}/*close main*/

void fill(FILE *main_program)
{
        Inventory  slot = {"",0,0.0,0};

        main_program=fopen("parts.txt","ab");

        fseek(main_program,0,SEEK_SET);
        fread(&slot,sizeof(Inventory),1,main_program);

        get_info(&slot);

        fseek(main_program,0,SEEK_SET);
        fwrite(&slot,sizeof(Inventory),1,main_program);

       

        fclose(main_program);

}/*close function*/

void get_info(Inventory *slot)
{
        gets_s(slot->partname,40);
        printf("Please enter partname\n");
        gets_s(slot->partname,40);

        printf("Please enter partnumber\n");
        scanf("%d", &slot->partnumber);

        printf("Please enter price\n");
        scanf("%d", &slot->price);

        printf("Please enter stock\n");
        scanf("%d", &slot->stock);

        printf("\n");

}/*close*/

---

however im having problems because when i select option one it doesnt return to menu but keep entering data.

Also id like to know if there are any ways of understanding exactly how to read and write from binary files because im having problems inderstanding.

thanks

Code:

---

        while(option!=5)
        {
                switch(option)
                {
                case 1:
                        fill(main);
                        break;

                }/*close switch*/

        }/*close while*/

---

There is nothing in this loop that changes "option", so it will never exit the loop if option != 5 to begin with.

--
Mats

God i have no idea how i didnt see it.

Also another question when one uses gets how come sometimes it skips it?

I end up having to write it twice any reason for that?

thanks again

EDIT

also id like some help understanding binary files and how they store information, thanks

> Also another question when one uses gets how come sometimes it skips it?
http://faq.cprogramming.com/cgi-bin/...&id=1043284392 Sort of explains it :)

Code:

---

scanf("%d", &slot->price);

---

Price is a float, not integer. Use %f.

Quote:

---

Originally Posted by Salnitro

God i have no idea how i didnt see it.

Also another question when one uses gets how come sometimes it skips it?

I end up having to write it twice any reason for that?

thanks again

EDIT

also id like some help understanding binary files and how they store information, thanks

---

gets will read up to the next newline. If you have a newline in the input buffer, it will read that and consider the task done. scanf() reads to the next whitespace (where newline is one of several "whitespace" characters), but leaves the whitespace itself in the input buffer, so gets() will then immediately see a newline. The correct solution is to get rid of the junk in the input buffer with something like this:

Code:

---

void inputflush(void)
{
  int ch;
  while((ch = getchar()) != '\n' && ch != EOF);
}

---

after any scanf [when switching to another input method than scanf, that is].

--
Mats

An even better way is to avoid scanf and use gets_s/fgets entirely. Then convert the string into an appropriate type using strtol/strtof/etc.

thanks for the great input, really learning a large amount here.

the conversion specifier problem i figured it out.

Regarding the scanf very interesting piece of information however considering ive been using it for 6 months i doubt i could do with out it, so for now ill use the double gets_s.

Last time my lecturer kinda asked me about the gets_s because he didnt know about the buffer! So i dont want to risk getting penalised by using different methods too much.

So here come more questions, ive added another function to the program, that is to search for a particular part number and modify the details, however im having problems because the program appears to discard the data already in the file and on occasions ignores files.

Is there a way to fix this?

new program

Code:

---

#include <stdio.h>

typedef struct inventory{
        char partname[40];
        int partnumber;
        float price;
        int stock;
       
}Inventory;

void fill(FILE *main_program);
void get_info(Inventory *slot);
void edit(FILE*main_program);
void edit_info(Inventory *slot);

int main (void)
{
        int option=0;
        FILE *main;

        main=fopen("parts.txt","ab");

        while(option!=5)
        {

                printf("PLEASE select from the following options\n");
                printf("1. Enter new part\n");
                printf("2. Edit existing part\n");
                printf("3. Sort part list by number and write output file\n");
                printf("5 Quit\n\n");

                scanf("&#37;d",&option);

       
                switch(option)
                {
                case 1:
                        fill(main);
                        break;

                case 2:
                        edit(main);
                        break;

                }/*close switch*/

        }/*close while*/

        fclose(main);

        return 0;

}/*close main*/


void edit(FILE*main_program)
{
        Inventory  slot = {"",0,0,0};
        int partnumber;
        int verify=1;
        int controller=1;

        main_program=fopen("parts.txt","rb+");

        printf("Please enter part number\n");
        scanf("%d", &partnumber);


        while(controller==1)
        {
                fseek(main_program,(verify-1)*sizeof(Inventory),SEEK_SET);
                fread(&slot,(verify-1)*sizeof(Inventory),1,main_program);

                if(partnumber==slot.partnumber)
                {
                        printf("Current details are:\n");
                        printf("Part name :  %s\n",slot.partname);
                        printf("Part price : %f\n",slot.price);
                        printf("Stock :      %d\n\n",slot.stock);
                        printf("************************************************\n");

                        edit_info(&slot);

                        fseek(main_program,(verify-1)*sizeof(Inventory),SEEK_SET);
                        fread(&slot,(verify-1)*sizeof(Inventory),1,main_program);
                        controller=0;
                }/*close if*/

                if(verify<=30)
                {
                        verify++;
                }/*close if*/

                if(verify>=30)
                {
                        printf("Part number not found, re enter number\n");
                        scanf("%d",&partnumber);
                        verify=1;
                }/*close if*/


               
        }/*close while*/

        fclose(main_program);
        printf("\n");
}/*close function*/



void fill(FILE *main_program)
{
        Inventory  slot = {"",0,0,0};

        main_program=fopen("parts.txt","ab");

        fseek(main_program,0,SEEK_SET);
        fread(&slot,sizeof(Inventory),1,main_program);

        get_info(&slot);

        fseek(main_program,0,SEEK_SET);
        fwrite(&slot,sizeof(Inventory),1,main_program);

       

        fclose(main_program);

}/*close function*/

void get_info(Inventory *slot)
{
        gets_s(slot->partname,40);
        printf("Please enter partname\n");
        gets_s(slot->partname,40);

        printf("Please enter partnumber\n");
        scanf("%d", &slot->partnumber);

        printf("Please enter price\n");
        scanf("%f", &slot->price);

        printf("Please enter stock\n");
        scanf("%d", &slot->stock);

        printf("\n");

}/*close*/

void edit_info(Inventory *slot)
{
        gets_s(slot->partname,40);
        printf("Please enter partname\n");
        gets_s(slot->partname,40);

        printf("Please enter price\n");
        scanf("%f", &slot->price);

        printf("Please enter stock\n");
        scanf("%d", &slot->stock);

        printf("\n");
}/*close */

---

Code:

---

        FILE *main;

        main=fopen("parts.txt","ab");

---

DO NOT EVER CALL A VARIABLE "main", ok?

It's also a good idea never to call variables the same name as any function.

Code:

---

void edit(FILE*main_program)
{
....
        main_program=fopen("parts.txt","rb+");

---

Don't open a file that is already opened elsewhere. (And this variable name is really not appropriate)

Code:

---

void fill(FILE *main_program)
{
        Inventory  slot = {"",0,0,0};

        main_program=fopen("parts.txt","ab");

        fseek(main_program,0,SEEK_SET);
        fread(&slot,sizeof(Inventory),1,main_program);

        get_info(&slot);

        fseek(main_program,0,SEEK_SET);
        fwrite(&slot,sizeof(Inventory),1,main_program);

       

        fclose(main_program);

}/*close function*/

---

You are always reading and writing the "inventory" data to position zero in the file - no surprise that it "ignores anything else you've entered".

--
Mats

Quote:

---

DO NOT EVER CALL A VARIABLE "main", ok?

It's also a good idea never to call variables the same name as any function.

---

will fix.

Quote:

---

Don't open a file that is already opened elsewhere. (And this variable name is really not appropriate)

---

were exactly?

Quote:

---

You are always reading and writing the "inventory" data to position zero in the file - no surprise that it "ignores anything else you've entered".

---

however when i input data i want that the program doesnt overwrite the other records so i think its ok, in the search function it ignores old data and acts really strangely.

thanks for the input though.

Quote:

---

Originally Posted by Salnitro

will fix.



were exactly?

---

Code:

---

        main=fopen("parts.txt","ab");

---

That's the same file you later on open in the edit and fill functions. You should only ever open the same file in one place. You DEFINITELY should not pass in a FILE pointer that has been opeend to another function, and then open a file into that file-pointer again, then close it before leaving the function - that is indeed very bad.

Quote:

---

however when i input data i want that the program doesnt overwrite the other records so i think its ok, in the search function it ignores old data and acts really strangely.

thanks for the input though.

---

I see nothing in your file that writes to any location other than 0, so how do you expect data to be anywhere other than at position zero? Can you please point out where you do that?

Also, after you have called "edit_info", you are READING the data again, not writing the updated data back.

--
Mats

Quote:

---

That's the same file you later on open in the edit and fill functions. You should only ever open the same file in one place. You DEFINITELY should not pass in a FILE pointer that has been opeend to another function, and then open a file into that file-pointer again, then close it before leaving the function - that is indeed very bad.

---

well i was told to open and close files and in the book were using (C how to program) the examples all show instances were files are opened and closed in each function.

I have no idea how to do otherwise.

Quote:

---

I see nothing in your file that writes to any location other than 0, so how do you expect data to be anywhere other than at position zero? Can you please point out where you do that?

---

well according to the book the command "ab" makes sure the file is pointing to the end therefore any added fields automatically go there (infact when i inspected the actual file they appear in the above manner).

Quote:

---

Also, after you have called "edit_info", you are READING the data again, not writing the updated data back.

---

i know however dont the two commands after the function call edit_info write the updated slot into the file?

It is fine to open and close the file within a function, but if you do so, then the FILE * that you are using for this should not be one that is passed from another function that also holds an already opened handle to the same file. You should NEVER open the same file more than once [unless you ABSOLUTELY KNOW what you are doing - and you have a quite few more lessons until you reach that stage].

However, if it is the same file that you open and close in each function, then it would be preferable to open the file once.

Code:

---

                        edit_info(&slot);

                        fseek(main_program,(verify-1)*sizeof(Inventory),SEEK_SET);
                        fread(&slot,(verify-1)*sizeof(Inventory),1,main_program);

---

fread does not WRITE to the file.

Quote:

---

well according to the book the command "ab" makes sure the file is pointing to the end therefore any added fields automatically go there (infact when i inspected the actual file they appear in the above manner)

---

Yes, but the "append" effect is negated by fseek(file, 0, SEEK_SET), which sets your file-position to the beginning of the file. And you do this twice in the "fill" function.

--
Mats

Quote:

---

Originally Posted by matsp

It is fine to open and close the file within a function, but if you do so, then the FILE * that you are using for this should not be one that is passed from another function that also holds an already opened handle to the same file. You should NEVER open the same file more than once [unless you ABSOLUTELY KNOW what you are doing - and you have a quite few more lessons until you reach that stage].

However, if it is the same file that you open and close in each function, then it would be preferable to open the file once.

Code:

---

                        edit_info(&slot);

                        fseek(main_program,(verify-1)*sizeof(Inventory),SEEK_SET);
                        fread(&slot,(verify-1)*sizeof(Inventory),1,main_program);

---

fread does not WRITE to the file.


Yes, but the "append" effect is negated by fseek(file, 0, SEEK_SET), which sets your file-position to the beginning of the file. And you do this twice in the "fill" function.

--
Mats

---

your right i removed the fseek and fixed the fread (i realised this after i posted forgot to edit)

i made the necassary changes yet i still have an error when searching, it misses the first field any idea why?

thanks for your help as its extremely usefull.

heres the updated program

Code:

---

#include <stdio.h>

typedef struct inventory{
        char partname[40];
        int partnumber;
        float price;
        int stock;
       
}Inventory;

void fill(FILE *fill_program);
void get_info(Inventory *slot);
void edit(FILE*edit_program);
void edit_info(Inventory *slot);

int main (void)
{
        int option=0;
        FILE *primary;

        primary=fopen("parts.txt","ab");

        while(option!=5)
        {

                printf("PLEASE select from the following options\n");
                printf("1. Enter new part\n");
                printf("2. Edit existing part\n");
                printf("3. Sort part list by number and write output file\n");
                printf("5 Quit\n\n");

                scanf("%d",&option);

       
                switch(option)
                {
                case 1:
                        fill(primary);
                        break;

                case 2:
                        edit(primary);
                        break;

                }/*close switch*/

        }/*close while*/

        fclose(main);

        return 0;

}/*close main*/


void edit(FILE*edit_program)
{
        Inventory  slot = {"",0,0,0};
        int partnumber;
        int verify=1;
        int controller=1;

        edit_program=fopen("parts.txt","rb+");

        printf("Please enter part number\n");
        scanf("%d", &partnumber);


        while(controller==1)
        {
                fseek(edit_program,(verify-1)*sizeof(Inventory),SEEK_SET);
                fread(&slot,(verify-1)*sizeof(Inventory),1,edit_program);

                if(partnumber==slot.partnumber)
                {
                        printf("Current details are:\n");
                        printf("Part name :  %s\n",slot.partname);
                        printf("Part price : %f\n",slot.price);
                        printf("Stock :      %d\n\n",slot.stock);
                        printf("************************************************\n");

                        edit_info(&slot);

                        fseek(edit_program,(verify-1)*sizeof(Inventory),SEEK_SET);
                        fwrite(&slot,(verify-1)*sizeof(Inventory),1,edit_program);
                        controller=0;
                }/*close if*/

                if(verify<=30)
                {
                        verify++;
                }/*close if*/

                if(verify>=30)
                {
                        printf("Part number not found, re enter number\n");
                        scanf("%d",&partnumber);
                        verify=1;
                }/*close if*/


               
        }/*close while*/

        fclose(edit_program);
        printf("\n");
}/*close function*/



void fill(FILE *fill_program)
{
        Inventory  slot = {"",0,0,0};

        fill_program=fopen("parts.txt","ab");

       
        fread(&slot,sizeof(Inventory),1,fill_program);

        get_info(&slot);

       
        fwrite(&slot,sizeof(Inventory),1,fill_program);

       

        fclose(fill_program);

}/*close function*/

void get_info(Inventory *slot)
{
        gets_s(slot->partname,40);
        printf("Please enter partname\n");
        gets_s(slot->partname,40);

        printf("Please enter partnumber\n");
        scanf("%d", &slot->partnumber);

        printf("Please enter price\n");
        scanf("%f", &slot->price);

        printf("Please enter stock\n");
        scanf("%d", &slot->stock);

        printf("\n");

}/*close*/

void edit_info(Inventory *slot)
{
        gets_s(slot->partname,40);
        printf("Please enter partname\n");
        gets_s(slot->partname,40);

        printf("Please enter price\n");
        scanf("%f", &slot->price);

        printf("Please enter stock\n");
        scanf("%d", &slot->stock);

        printf("\n");
}/*close */

---

Perhaps because of this:

Code:

---

                fread(&slot,(verify-1)*sizeof(Inventory),1,edit_program);

---

You should not multiply the size of what you read with verify-1 in the first place, and in the first record, this becomes zero, so you read nothing.

--
Mats