Thread: program failing while trying to open/create file

r+ read and write text mode
w+ read and write text mode (truncates file to zero length or creates new file)

My guess is that you want to use "w+".

The "r+" mode doesn't create the file. If it exists, it opens it for reading and writing. If it doesn't exist, fopen() returns NULL.

The "w+" mode works only slightly differently. If it exists, it truncates the file and opens it reading and writing. If it doesn't exist, the file is created and then opened for reading and writing.

But it sounds like what you want is actually "a+". If the file exists, it's opened (but not truncated) for reading and writing. If it doesn't exist, it's created and opened for reading and writing. The only caveat is that the you'll need to reposition the stream to the beginning of the file if you want to read from the file. You can do this by simply using:

fseek(auto_file, 0, SEEK_SET);

...after opening the file.

Check here for more information.

Actually you don't have to escape slashes if you're using a string passed from the user, because it automatically does it for you. Simply fgets some text into a buffer, with slashes in it, and print it out, you'll see what I mean.


Quzah.

Code:

                if(path[loop] != '\\')
                    path[loop] = '\0';
                else if(path[loop] == '\\')
                    break;

You don't need the second if(). It works just as well with just else.

However,

Code:

    for(loop = 0; loop < 256; loop++)
    {
        if(path[loop] == '\0')
        {
            while(loop > 0)
            {
                if(path[loop] != '\\')
                    path[loop] = '\0';
                else if(path[loop] == '\\')
                    break;
                loop--;
            }
            break;
        }
    }
    strcpy(path+loop+1, "cars.aut");

This whole thing could be replaced with:

Code:

{
  char *p;

  if((p = strrchr(path, '\\')))
    p++;
  else
    p = path;

  strcpy(p, "cars.aut");
}

...and I think it makes it a little bit clearer what you're actually trying to do.

Well, the other thing is, if you're expecting the changes you make to path in your filepath_edit() function to be returned to the calling function then you're doing it wrong. Your filepath_edit() function is passed a copy of the pointer and then modifying that local pointer. The path variable in the calling function is unaffected.

What you'll need to do instead is pass a pointer to a pointer to your filepath_edit() function (e.g. filepath_edit(&path)). This will change your function somewhat:

Code:

int filepath_edit(char **path, char **argv)
{
  char *p;

  *path = argv[0];

  if((p = strrchr(*path, '\\')))
    p++;
  else
    p = *path;

  strcpy(p, "cars.aut");
  puts(*path);

  return 0;
}

Edit: ^ Definitely fix that first

You'll probably need to re-post your code.
Maybe all of it instead of a snippet.
You've likely made changes.

The only thing I see wrong with your last piece of code is if yes_or_no == 'y' you never even attempt to open a file.

Does yes_or_no actually equal 'y' or 'n'?
is auto_file declared correctly as a FILE pointer?
are you sure you're looking in the right spot for the created file? (sounds like you are).

Maybe try something simple like just opening and writing to a file.
The actual problem may be elsewhere.

Code:

#include <stdio.h>

int main( void )
{
    FILE *fp;
    fp = fopen("TEST.txt", "w+");

    if(fp == NULL) {
        printf("Failed to open file TEST.txt\n");
        return -1;
    }

    fprintf(fp, "%s", "Hello World\n");

    fclose(fp);

    return 0;
}