CODEWITHSUNDEEP
cwhile-loopscanfstrcmp
Freedom
Freedom

Reputation: 347

strcmp and fscanf with a While Loop through a file

I'm having trouble with a specific line of code that is giving me the errors of

error: invalid conversion from ‘int’ to ‘const char*’

error: initializing argument 1 of ‘int strcmp(const char*, const char*)’

Does anyone happen to know why? This is the line of code in question.

while (strcmp(fscanf(fr, "%s", words), "DONE") != 0)

Essentially, my code scans through a file (performing certain operations) until it reaches the key word of "DONE" (without the quotes), at which it exits the file. I'm a beginner C programmer so forgive any inaccuracies/inefficiencies in code.

The full code is below.

#include <stdio.h>
#include <string.h>

FILE *fr;

struct player {
    char name[50];
    float DOC;

};

struct player players[50];

int main() {
    fr = fopen ("playerinfo.txt", "r");

    if (ftell(fr) == 0) {
        fclose(fr);
        printf("PLAYER FILE IS EMPTY");
        return 0;
    }

    char words[50];

    while (strcmp(fscanf(fr, "%s", words),"DONE") != 0) {
        float pts;
        fscanf(fr, "%f", pts);

        float asts;
        fscanf(fr, "%f", asts);

        float mins;
        fscanf(fr, "%f", mins);

        struct player *aPlayer;
        float theDOC = (pts + asts) / mins;
        strcpy(aPlayer->name, words);
        aPlayer->DOC = theDOC;
    }

    fclose(fr);

    return 0;
}

Upvotes: 0

Views: 661

Answers (2)

Benjamin Barrois
Benjamin Barrois

Reputation: 2686

The problem is in your strcmp() function. Indeed, when you do:

strcmp(fscanf(fr, "%s", words),"DONE")

you compare the return of fscanf (which is an int) to the const char * "DONE". This is impossible. You need to compare directly words with "DONE".

You should do something like:

int test;
test = fscanf(fr, "%s", words);
while ((test != EOF) && (strcmp(words,"DONE") != 0)) {

         float pts;
         fscanf(fr, "%f", pts);

         float asts;
         fscanf(fr, "%f", asts);

         float mins;
         fscanf(fr, "%f", mins);

         struct player *aPlayer;
         float theDOC = (pts + asts) / mins;
         strcpy(aPlayer->name, words);
         aPlayer->DOC = theDOC;

         test = fscanf(fr, "%s", words);
}

Upvotes: 1

Sourav Ghosh
Sourav Ghosh

Reputation: 134386

In your code,

  strcmp(fscanf(fr, "%s", words),"DONE")

does not do what you think it does. fscanf() does not return a pointer to the scanned string, rather, it returns a count (int type). Your compiler warned you. Read the man page before you proceed.

This improper usage causes the warning.

That said, you must check for the success of scanf() family of functions, otherwise, you have a very high possibility of ending up with using indeterminate values (think of the content of words, if scanning fails).

So, you break the operations into two parts.

  • use fgets() / fscanf() to intake the input (newline trimming, if needed). Check for success of the call.
  • compare the input buffer with the required string (strcmp()).

That said, I really don't see much point of the whole loop, as you'll be creating a new local variable aPlayer every time you enter the loop. I hope you know what you're doing.

Disregarding above case, a generic flow should look like

input = "Not Done";
while ('input' is not "Done")
     scan values;
     check for succss;
     store into variables;
     scan next 'input'

Upvotes: 2

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