User-specified input file issue.

Hi all, I've recently started programming at university and am having a bit of trouble with it. I've begun a piece of work that requires the user to enter a filename, read it into an array, do some maths/statistics and display a variety of results in tables. Annoyingly, I can't get the first part working - my attempt thus far is as follows;

Code:

---

#include<stdio.h>
#include<math.h>
#include<string.h>
int main(void)
{
        char filename[25];
        int numbers;

        FILE * fptr;
        printf("Please enter a filename: ");
        scanf(" %24s",filename[25]);
        fptr=fopen(filename[25],"r");
        if (fptr==NULL) printf("Open failed.");
        while(fscanf(fptr," %d",&numbers)!=EOF)
                printf(" %3d",numbers);
        fclose(fptr);
       
    getchar();
    getchar();
    return 0;
}

---

The program seems to freeze as soon as I type in the filename and hit enter; I was under the impression that the scanf would read in whatever I typed to filename[25], so if I typed for example "statsdata.txt", this would then open the file as if I'd simply typed fptr=fopen("statsdata.txt","r"); normally, so I'm not sure what to do!

Also, in my file I have 8 numbers seperated by whitespace; if I type out the fptr=fopen("statsdata.txt","r"), these numbers are displayed onscreen. I'm unsure though if these are now in an array or not - is filename[25] here considered to be a string and unrelated to the numbers within?

The program required is pretty complex for my current knowledge, kind of stressing about it which doesn't help either. Thanks a lot for any help you can give.

Code:

---

#include<stdio.h>
#include<math.h>
#include<string.h>
int main(void)
{
        char filename[25];
        int numbers;

        FILE * fptr;
        printf("Please enter a filename: ");
        scanf(" %24s",filename[25]);
        fptr=fopen(filename[25],"r");
        if (fptr==NULL) printf("Open failed.");
        while(fscanf(fptr," %d",&numbers)!=EOF)
                printf(" %3d",numbers);
        fclose(fptr);
       
    getchar();
    getchar();
    return 0;
}

---

To start, the bits in red should be eliminated.

Ah, I see, that's sorted it out. Seems such a basic mistake..going to have to read over my notes again (and again) and improve general c knowledge I think!

Thanks again, hopefully can make some progress with the rest of it now. :)

Yep - in that case, you want just the name of the char array, filename. When you use the just the name, it is the same as doing filename[0]. What you had done was pass it an address to the end of the array, which is usually not good.

Sometimes it is good to just test things on a smaller scale. Just work on the part to do with getting the user input, and then print it out. If you get that working, then you can use the name of the file to open the file with fopen.

Quote:

---

Originally Posted by kermit

Yep - in that case, you want just the name of the char array, filename. When you use the just the name, it is the same as doing filename[0].

---

To be clear, it's the same as doing &filename[0]. filename[0] is just a single character, &filename[0] or just filename refer to the address of the first element, which is how you refer to "strings" in C.

Quote:

---

Originally Posted by anduril462

To be clear, it's the same as doing &filename[0]. filename[0] is just a single character, &filename[0] or just filename refer to the address of the first element, which is how you refer to "strings" in C.

---

Indeed. Good catch on a sloppy answer from me.