Thread: Checking for file existence

Can anyone suggest how I can check for a files existence prior to using it...

I have found a code called F_OK - but am not sure of the syntax to use it.

many thanks
Sue

Except "r+" will create the file if it doesn't exist
Perhaps "r"

I think the F_OK you found is from the access (or _access) function. I don't know which OS/compiler you are using and if your compiler supports the function but here's an example:

Code:

#include  <io.h>
#include  <stdio.h>
#include  <stdlib.h>

int main()
{
  // 0 = check for existence, 2 = check for write permission
  // 4 = check for read permission, 6 = check for read/write permission
  if(_access( "C:\\file.xt", 0 ) != -1)
  {
    printf("File exists\n");

    if(_access( "C:\\file.txt", 2 ) != -1)
      printf("File has write permission\n");
  }
}

This (above) is a windows example. If you are using unix/linux and the access function is supported you probably need to include unistd.h and you can use R_OK, W_OK, X_OK and F_OK.

Code:

#include  <unistd.h>
#include  <stdio.h>
#include  <stdlib.h>

int main()
{
  if(access("file.xt", F_OK) != -1)
  {
    printf("File exists\n");

    if(access("file.txt", R_OK|W_OK) != -1)
      printf("File has read/write permission\n");
  }
}

Regards,
Monster