Thread: strange behaviour

Hi all.

If "test.txt" contains "Hello world", and this is copied into "temp.txt", then why does puts(word) result in "hhhhh"? Why not "Hello"? Thanks in advance.

Code:

// spellcheck.c - checks spelling of a text file against a dictionary file
// 5 functions: copyfile(), getword(), spellcheck(), options(), editfile()

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

#define BUFFERSIZE 4096
#define FILENAME_LENGTH 40
#define STRING_LENGTH 300 // length of string read by fgets() from file
#define WORD_LENGTH 40

void copyfile (FILE *file, FILE *tempfile);
void getword(FILE *tempfile);
void spellcheck (char *word);
void options();
void edit_file();

int main(void)
{
    FILE *file, *dictionary, *tempfile;
    char word_to_check[WORD_LENGTH];

    file = fopen("test.txt", "r");
    tempfile = fopen("temp.txt", "w");
    copyfile(file, tempfile);
    tempfile = fopen("temp.txt", "r");
    getword(tempfile);
    //dictionary = fopen("dictionary.txt", "r");

    //spellcheck(word_to_check);

    return 0;
}

// copy original file to tempfile for reading so that original file can be opened for writing(editing)
void copyfile(FILE *file, FILE *tempfile)
{
    size_t c;
    char buffer[BUFFERSIZE];

    while((c = fread(buffer, 1, BUFFERSIZE, file)) > 0)
    {
        fwrite(buffer, 1, c, tempfile);
    }
    fclose(file);
    fclose(tempfile);
}

void getword(FILE *tempfile)
{
    char word[WORD_LENGTH];
    int ch;
    static int x1 = 0, x2 = 0; // location of space or punctuation
    int ctr = 0;

    while((ch = fgetc(tempfile)) != EOF)
    {
        if((ch != ' ') && (ch != '.') && (ch != '-') && (ch != '!') && (ch != '(') && (ch != ')') && (ch != ':') && (ch != ';') && (ch != '\n'))
        {
            word[ctr] = 'ch';
            ctr++;
            continue;
        }
        else
        {
            word[ctr] = '\0'; // if ch is space or punctuation, add terminator to create string
            puts(word);
            exit (1);
        }
    }
}

//void spellcheck (char *word)
//{
//
//}

> word[ctr] = 'ch';
Because this is a wide character constant, and the LSB of it is just 'h'

Perhaps you meant
word[ctr] = ch;

> exit (1);
This is a bit aggressive having just read one word, what about the rest of the file?

> fclose(file);
> fclose(tempfile);
There is nothing wrong per se, but it might be an idea to open and close the files in the same function.
Leaked file handles (caused by confusion over who opens/closes the file) are pretty serious, since there are so few file handles to begin with.

Thanks for the replies. Such a simple mistake, but I still couldn't figure it out after 2 hours.

Maybe I'll ask here next time if I can't solve something within an hour.

You're using gcc, so you should be able to enable these options.

Code:

$ gcc -std=c99 foo.c
foo.c: In function ‘getword’:
foo.c:61:25: warning: multi-character character constant [-Wmultichar]
foo.c:61:13: warning: overflow in implicit constant conversion [-Woverflow]

$ gcc -Wall -std=c99 foo.c
foo.c: In function ‘main’:
foo.c:22:10: warning: unused variable ‘word_to_check’ [-Wunused-variable]
foo.c:21:18: warning: unused variable ‘dictionary’ [-Wunused-variable]
foo.c: In function ‘getword’:
foo.c:61:25: warning: multi-character character constant [-Wmultichar]
foo.c:61:13: warning: overflow in implicit constant conversion [-Woverflow]
foo.c:54:24: warning: unused variable ‘x2’ [-Wunused-variable]
foo.c:54:16: warning: unused variable ‘x1’ [-Wunused-variable]

Well, the code is starting to take shape, but I am getting the below errors.

I declared the struct in getword(), and want to pass the struct back to main. How do I create a pointer to the struct in main, and assign the returned struct to it? I tried to do this in line 22, but the struct is local to getword(). Thanks.

Code:

main.c||In function ‘main’:|
main.c|30|error: request for member ‘word’ in something not a structure or union|
main.c|31|error: request for member ‘word’ in something not a structure or union|
main.c|34|warning: comparison between pointer and integer [enabled by default]|
main.c|22|warning: variable ‘word_to_check’ set but not used [-Wunused-but-set-variable]|
main.c|21|warning: variable ‘dictionary’ set but not used [-Wunused-but-set-variable]|
main.c||In function ‘getword’:|
main.c|79|warning: return from incompatible pointer type [enabled by default]|
main.c|79|warning: function returns address of local variable [enabled by default]|
main.c|82|warning: return makes pointer from integer without a cast [enabled by default]|
main.c|64|warning: unused variable ‘x2’ [-Wunused-variable]|
main.c|64|warning: variable ‘x1’ set but not used [-Wunused-but-set-variable]|
||=== Build finished: 2 errors, 8 warnings ===|

Code:

// spellcheck.c - checks spelling of a text file against a dictionary file
// 5 functions: copyfile(), getword(), spellcheck(), options(), editfile()

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

#define BUFFERSIZE 4096
#define FILENAME_LENGTH 40
#define STRING_LENGTH 300 // length of string read by fgets() from file
#define WORD_LENGTH 40

void copyfile (FILE *file, FILE *tempfile);
struct word *getword(FILE *tempfile);
void spellcheck (struct word *word_to_check);
void options();
 void editfile();

int main(void)
{
    FILE *file, *dictionary, *tempfile;
    struct word *word_to_check;

    copyfile(file, tempfile);
    tempfile = fopen("temp.txt", "r");
    dictionary = fopen("dictionary.txt", "r");

    do {
        word_to_check = getword(tempfile);
        printf("%s", word_to_check.word);
        spellcheck(word_to_check.word);
    //option();
    //edit();
    } while (getword(tempfile) != 1);

    return 0;
}

// copy original file to tempfile for reading so that original file can be opened for writing(editing)
void copyfile(FILE *file, FILE *tempfile)
{
    size_t c;
    char buffer[BUFFERSIZE];

    file = fopen("test.txt", "r");
    tempfile = fopen("temp.txt", "w");

    while((c = fread(buffer, 1, BUFFERSIZE, file)) > 0)
    {
        fwrite(buffer, 1, c, tempfile);
    }
    fclose(file);
    fclose(tempfile);
}

struct word *getword(FILE *tempfile)
{
    struct word {
    char word[WORD_LENGTH];
    int x;
    } word;

    int ch;
    static int x1 = 0, x2 = 0; // location of space or punctuation
    int ctr = 0;

    while((ch = fgetc(tempfile)) != EOF)
    {
        if((ch != ' ') && (ch != '.') && (ch != '-') && (ch != '!') && (ch != '(') && (ch != ')') && (ch != ':') && (ch != ';') && (ch != '\n'))
        {
            word.word[ctr] = ch;
            ctr++;
            x1 = ctr;
            continue;
        }
        else
        {
            word.word[ctr] = '\0'; // if ch is space or punctuation, add terminator to create string
            return &word; // return pointer to main()
        }
    }
    return (word.x = 1); // flag that EOF has been reached
}

void spellcheck (struct word *word_to_check)
{

}

Lines 58 to 61 need to be moved to around line 12

Make the struct global? That would make things so easy. But people keep telling to stop using globals(including structs).

Oh well, if you say so.

It's global variables (of any type) which people say to avoid.

A struct declaration is like a function prototype. It has to be declared in a place visible to everything that uses it.

So towards the beginning of the file

Code:

// a struct called word, containing members called word and x
    struct word {
    char word[WORD_LENGTH];
    int x;
    };

And in your function

Code:

struct word word;  // create an instance of 'struct word' called 'word'

Originally Posted by AndiPersti

But that line is wrong because you have defined the function to return a pointer and here you try to return an int.
If you want to return some kind of error message to the caller you have to use a pointer. Usually that's done with a null-pointer.

That's great. My only reason for using a struct is so that I could return an int to signify EOF. If I can just return a null pointer, then time to get rid of the struct altogether.