how to validate user input in file name

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I want to program that file name input that allow the user 3 chances to enter a valid file name. If a valid file name is not entered after 3 chances, terminate the program.
else print successful message

Posted 14-Mar-13 2:33am

Venkat Raghvan

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2 solutions

Solution 2

Are you asking for code to check for a valid filename or that a particular filename exists already on the file system?

For the latter:

C++

int fileExists(TCHAR * file)
{
   WIN32_FIND_DATA FindFileData;
   HANDLE handle = FindFirstFile(file, &FindFileData) ;
   int found = handle != INVALID_HANDLE_VALUE;
   if(found) 
   {
       FindClose(&handle);
   }
   return found;
}

This code looks to see if a file exists without opening it.

Posted 14-Mar-13 11:15am

H.Brydon

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CPallini · Accepted Answer · 2013-03-14T02:43:00

That usually depend on what you mean with 'valid filename', e.g. Should its path be formally correct? Should it be an existing file? Should it be a new file? ("Should we buy a new guitar?").
Depending on your needs you have to build your validation function (it might be very simple, e.g. just trying to open the file). Once you have the validation function you have only to keep track of failed attempts and close the program if this number becomes 3.

[Update]
I would use

C

int i;
FILE fp = NULL;
for (i=0; i<3; i++)
{
  printf("\n\nEnter filename :" );
  gets( fname );
  fp = fopen (fname, "r");
  if (fp)
    break;
  printf("Cannot open %s for reading \n", fname );
}
if ( ! fp ) return -1; // exit the program here
// fp is OK here, you may continue...

[/Update]