Checking a file for matching string - c

Question

I'm writing a program that allows multiple users to create, save, and load data to files. I'm running into an issue where I can't find seem to figure out a logic that doesn't allow users to create duplicate file names.
Here is the important working part of my code thus far, but where my issues are. The variable user is assigned at the launch of my program where the user must enter their username and password.
else if (selection == 6)
{
int i;
int d;
printf("Please enter a file name: ");
scanf("%s", filename);
newFile = fopen(filename, "a+");
Record = fopen("records.txt", "a+");
fprintf(Record, "%s %s\n", user, filename);
for (i = 0; i < icount; i++)
{
fprintf(newFile, "%d ", ints[i]);
}
for (d = 0; d < dcount; d++)
{
fprintf(newFile, "%lf ", doubles[d]);
}
fclose(Record);
fclose(newFile);
}
else if (selection == 7)
{
printf("Please enter a file name: ");
scanf("%s", filename);
Record = fopen("records.txt", "a+");
while (fscanf(Record, "%s %s", curuser, curfile) != EOF)
{
if (strcmp(user, curuser) == 0 && strcmp(filename, curfile) == 0)
{
int c;
//fopen(newFile, "a+");
newFile = fopen(filename, "a+");
if (newFile) {
while ((c = getc(newFile)) != EOF)
{
putchar(c);
}
fclose(newFile);
break;
}
}
else
{
printf("You don't have access to this file.\n");
break;
}
}
}
Somewhere in selection 6, I'm trying to say in code, "Okay user, enter a file, unless the name already exists." What I tried was
while (fscanf(Record, "%s %s", curuser, curfile) != EOF)
{
if (strcmp(curfile, filename) == 0)
{
break;
}
else
{
fprintf(Record, "%s %s\n", user, filename);
fclose(Record);
}
}
and I'm unable to figure out why this won't work. I tried placing this code right below Record file declaration.
I think the issue may be that when the record file is empty, the != EOF line is causing it to break, but I also can't figure out a way to initially get one user and filename in the record before probing the rest of the users for their filenames. Any guidance in the right direction would be appreciated!

Answer 1

I think you can solve your problem by cutting the while loop in several parts:
do the fscanf
check for end of file
check for "user found"
And finally,
write user if not previously in file.
I would have written something like:
int record_found = 0;
int scanf_res;
while (1)
{
/* do the fscanf */
scanf_res = fscanf(Record, "%s %s", curuser, curfile);
/* test for end of file */
if (EOF == scanf_res)
{
/* end of file reached */
break;
}
/* if fscanf has mado 2 conversion AND
filename is curfile */
if ((2 == scanf_res) && (strcmp(curfile, filename) == 0))
{
record_found = 1;
break;
}
}
if (!record_found)
{
/* add user if needed */
fprintf(Record, "%s %s\n", user, filename);
}
/* and close file in all cases */
fclose(Record);