我将如何使用 strtok 逐字比较

Question

I've been reading up on strtok and thought it would be the best way for me to compare two files word by word. So far i can't really figure out how i would do it though

Here is my function that perfoms it:

int wordcmp(FILE *fp1, FILE *fp2)
{
   char *s1;
   char *s2;
   char *tok;
   char *tok2;
   char line[BUFSIZE];
   char line2[BUFSIZE];
   char comp1[BUFSIZE];
   char comp2[BUFSIZE];
   char temp[BUFSIZE];
   int word = 1;
   size_t i = 0;

while((s1 = fgets(line,BUFSIZE, fp1)) && (s2 = fgets(line2,BUFSIZE, fp2)))
{
    ;
}

tok = strtok(line, " ");
tok2 = strtok(line, " ");

while(tok != NULL)
{
    tok = strtok (NULL, " ");

}


return 0;
}

Don't mind the unused variables, I've been at this for 3 hours and have tried all possible ways I can think of to compare the values of the first and second strtok. Also I would to know how i would check which file reaches EOF first.

when i tried

  if(s1 == EOF && s2 != EOF)
  {
      return -1;
  }

It returns -1 even when the files are the same? Is it because in order for it to reach the if statement outside of the loop both files have reached EOF which makes the program always go to this if statement?

Thanks in advance!

Answer 1

If you want to check if files are same try doing,

    do {
       s1 = fgetc(fp1);
       s2 = fgetc(fp2);

       if (s1 == s2) {
            if (s1 == EOF) {
                return 1; // RETURN TRUE
            }
            continue;
      }
      else {
        return -1;  // RETURN FALSE
      }

  } while (1);

Good Luck:)

Answer 2

When you use strtok() you typically use code like this:

tok = strtok(line, " ");
while (NULL != tok)
{
    tok = strtok(NULL, " ");
}

The NULL in the call in the loop tells strtok to continue from after the previously found token until it finds the null terminating character in the value you originally passed (line) or until there are no more tokens. The current pointer is stored in the run time library, and once strtok() returns NULL to indicate no more tokens any more calls to strtok() using NULL as the first parameter (to continue) will result in NULL. You need to call it with another value (eg another call to strtok(line, " ")) to get it to start again.

What this means is that to use strtok on two different strings at the same time you need to manually update the string position and pass in a modified value on each call.

tok = strtok(line, " ");
tok2 = strtok(line2, " ");
while (NULL != tok && NULL != tok2)
{
    /* Do stuff with tok and tok2 here */
    if (strcmp(tok, tok2)... {}
    /* Update strtok pointers */
    tok += strlen(tok) + 1;
    tok2 += strlen(tok2) + 1;
    /* Get next token */
    tok = strtok(tok, " ");
    tok2 = strtok(tok2, " ");
}

You'll still need to add logic for determining whether lines are different - you've not said whether the files are equivalent if a line break occurs at different position but the words surrounding it are the same. I assume it should be, given your description, but it makes the logic more awkward as you only need to perform the initial fgets() and strtok() for a file if you don't already have a token. You also need to look at how files are read in. Currently your first while loop just reads lines until the end of the file without processing them.