Thread: file somethingsomething

heres a piece of my code :

FILE *f;
f=fopen("dump.df","w");
if(!f)
{
printf("Could not open dump.df\n");
return 1;
}

i was wondering if there is a possible way of making the filename
>> "dump.df" being asked from the user ?

something like:

scanf("%s", ??);
FILE *f;
f=fopen("%s","w"), ??;
if(!f)
{
printf("Could not open dump.df\n");
return 1;
}

hmmmmm.... thats odd. it only gives me errormessages when i run it

Code:

FILE *f;
char filename[255];

puts(" Enter Filename: ");
gets(filename);
f=fopen(filename,"w"); 
if(!f) 
{ 
printf("Could not open %s\n", filename); 
return 1; 
}

Originally posted by Unregistered
hmmmmm.... thats odd. it only gives me errormessages when i run it

That's because the fgets function also includes the newline character in your buffer.
Remove the newline character from your buffer after the fgets function:

Code:

buffer[strlen(buffer)-1] = '\0';

Try to avoid functions like gets and scanf.
With these functions you can get a buffer overflow:

Code:

int main()
{
  char buf[10];
  gets(buf);
  return 0;
}

If the user enters more than 10 characters the application can crash (access violation) because there is only space for 10 characters.

> Try to avoid functions like gets and scanf.

That's a valid point. Try to use 'fgets(..., stdin)' instead!

thx for all ur support... i think ive got it now

this is beginning to be veryvery strange (atleast for my skill)

this is my full code >>

#include <stdio.h>

int main()
{
clrscr();
printf("=[ Dumpfile creator ]=\n\nEnter size in Mb: ");
FILE *f;
f=fopen("dump.df","w");
if(!f)
{
printf("Could not open dump.df\n");
return 1;
}
int luku, x, x2, iso;
int kohta=10000, koko=59000;
float mgs=1;
scanf("%d", &x2);
x = x2 * 59000;
printf("\n\n\n");
while(luku<=x)
{
fprintf(f, "%d%d\n",luku, iso);
luku=luku+1;
iso=iso+luku;
if(luku == koko)
{
clrscr();
koko=koko+59000;
printf("Total size: %6.2f Mb", mgs);
mgs=mgs+1;
}
}
printf("\n\n\nWrite completed to dump.df\n");
printf("Code by Metael\n");
fclose(f);
}


now ... u told me how to make it ask the file name...

it should look like this then >>

#include <stdio.h>

int main()
{
clrscr();
printf("=[ Dumpfile creator ]=\n\nEnter Filename: ");
FILE *f;
char filename[255];
gets(filename);
f=fopen(filename,"w");
if(!f)
{
printf("Could not open %s\n", filename);
return 1;
}
int luku, x, x2, iso;
int kohta=10000, koko=59000;
float mgs=1;
printf("\nEnter size in Mb: ");
scanf("%d", &x2);
x = x2 * 59000;
printf("\n\n\n");
while(luku<=x)
{
fprintf(f, "%d%d\n",luku, iso);
luku=luku+1;
iso=iso+luku;
if(luku == koko)
{
clrscr();
koko=koko+59000;
printf("Total size: %6.2f Mb", mgs);
mgs=mgs+1;
}
}
printf("\n\n\nWrite completed to %s\n", filename);
printf("Code by Metael\n");
fclose(f);
}

now when i compile and run this... it stops somewhere around

scanf("%d", &x2);
x = x2 * 59000;
printf("\n\n\n");
<< here >>
while(luku<=x)
{

or something and just creates the file as long as i have enough space on my harddrive, doesnt show the progress as it should and is very irrating because i dont know what to do..

Some tips:

- Begin your main with declaring all your variables
- You are using the var luku in your while loop without initializing it
- Same story for the var iso
- int main() -> return something at the end of main
- gets(filename); -> this can result in a buffer overflow (if the user enters more than 255 characters). Try fgets instead (but watch out for the newline char):

Code:

fgets(filename, 255, stdin);
if(filename[strlen(filename)-1] == '\n')
  filename[strlen(filename)-1] = '\0';

Cheers,
Monster