Thread: Problems passing file path names with spaces into function

Hi all,
I am writing a C function that can be called through R and am running into problems with passing file path name strings that contain spaces. I know it is bad practice to have spaces in path names, but I am writing the program for other non-computer folks to use and so it has to handle spaces.

Example path name: C:/Project/My Folder/output.csv

If I type the path name in quotes directly into the test function below, it works fine. (The char ** argument for the function is a quirk of using the .C call in R to pass strings).

Code:

void dummy_function(char **my_output_file)
{   
   char path[300];
   strcpy(path, *my_output_file);
   
  FILE *MyFile = fopen("C:/Project/My Folder/output.csv","w"); 
    fprintf(MyFile, "%d,%d\n", 5,6);
   fclose(MyFile); 
}

I tried a very hack way of pasting quotes around the input text string. It prints back console as "C:/Project/My Folder/output.csv", but it is not recognized by fopen().

Code:

void dummy_function(char **my_output_file)
{
     
   char path[300];
   strcpy(path, *my_output_file);
 
   char start_quotes[300] = "\"";
   strcat(start_quotes, path);
   
   char end_quotes[300] = "\"";
   strcat(start_quotes, end_quotes);
   
  FILE *MyFile = fopen(start_quotes,"w"); 
    fprintf(MyFile, "%d,%d\n", 5,6);
    fclose(MyFile); 
}

Is there a better way to make this work?
Thanks!

It is not "bad practice" to have spaces in file names. All programs should be able to handle spaces in file names.

You can't just add quotes to the file name. Do you think the quotes are part of the file name in your first example fopen call? They simply delimit the string. Have you tried it without adding the quotes? What is the result?

What is the exact contents of "test.txt" with this:

Code:

void dummy_function(char **out) {
         FILE *f = fopen("test.txt", "w");
         fprintf(f, "[%s]\n", *out);
         fclose(f);
}

Hi Salem,
The literal string works absolutely fine and it look like the entire string is passing through the function. That's why I thought trying to paste quotes around it might work, but there must be some other weird formatting issue with the space. There is unfortunately not much useful documentation for this particular R to C problem.

Hi Algorism,
The exact output is [C:/Project/My Folder/output.csv] so it looks like there are no weird formatting characters with the spaces. How do I get C to recognize the string as a file path name?
Thanks

Hi c99tutorial,
As far as I can tell, when I type:

Code:

FILE* fp = fopen("C:/Project/My Folder/output.csv", "w");
    fprintf(fp, "Hello. This is foo.csv.\n");
    fclose(fp);

It writes the text into the file just fine.

However, when I try

Code:

char path[300];
strcpy(path, *my_output_file);
FILE *MyFile = fopen(path,"w"); 
  if(MyFile == NULL)
     {
           Rprintf("Error");
     }
fclose(MyFile);

It can't open the file and returns the Error message to R. I checked in the response to Algorism to make sure there were no weird formatting things in the string, but it appears to be correct. Does it need to have quotes around it for C to recognize it as a path with spaces?

Originally Posted by NotAProgrammer

Hi Algorism,
The exact output is [C:/Project/My Folder/output.csv] so it looks like there are no weird formatting characters with the spaces. How do I get C to recognize the string as a file path name?
Thanks

If that worked, then this should work:

Code:

void dummy_function(char **my_output_file) {   
    FILE *MyFile = fopen(*my_output_file, "w"); 
    fprintf(MyFile, "%d,%d\n", 5, 6);
    fclose(MyFile); 
}