C check if file exists

cc89

In a project I have to do in C89 standard I have to check if a file exists.
How do I do this?

I thought of using

FILE *file;
if ((file = fopen(fname, "r")) == NULL)
{
  printf("file doesn't exists");
}
return 0;

but I think there can be more cases then file doesn't exists that will do fopen == NULL.

How do I do this? I prefer not using includes rather then .

Best Answer

If you can't use stat() in your environment (which is definitely the better approach), just evaluate errno. Don't forget to include errno.h.

FILE *file;
if ((file = fopen(fname, "r")) == NULL) {
  if (errno == ENOENT) {
    printf("File doesn't exist");
  } else {
    // Check for other errors too, like EACCES and EISDIR
    printf("Some other error occured");
  }
} else {
  fclose(file);
}
return 0;

Edit: forgot to wrap fclose into a else

Related Solutions

Printing leading 0’s in C

printf("%05d", zipCode);

The 0 indicates what you are padding with and the 5 shows the width of the integer number.

Example 1: If you use "%02d" (useful for dates) this would only pad zeros for numbers in the ones column. E.g., 06 instead of 6.

Example 2: "%03d" would pad 2 zeros for one number in the ones column and pad 1 zero for a number in the tens column. E.g., number 7 padded to 007 and number 17 padded to 017.

What’s the best way to check if a file exists in C

Look up the access() function, found in unistd.h. You can replace your function with

if( access( fname, F_OK ) == 0 ) {
    // file exists
} else {
    // file doesn't exist
}

You can also use R_OK, W_OK, and X_OK in place of F_OK to check for read permission, write permission, and execute permission (respectively) rather than existence, and you can OR any of them together (i.e. check for both read and write permission using R_OK|W_OK)

Update: Note that on Windows, you can't use W_OK to reliably test for write permission, since the access function does not take DACLs into account. access( fname, W_OK ) may return 0 (success) because the file does not have the read-only attribute set, but you still may not have permission to write to the file.

Best Answer

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Printing leading 0’s in C

What’s the best way to check if a file exists in C

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