How to search for the number of times a word appears in a text file

Question

I'm trying to write a program that i have to enter a word from the keyboard and then it will check how much times appears in a text file using the strcmp() function. here is my code. i can write the word but when i enter the enter button the program stops. anyone can help me to figured out whats going wrong?

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


int main()
{
char input[20];
char string[20];
int num = 0;


FILE *text;

printf("Enter a word:\n");
scanf_s("%s\n", &input);

fopen_s(&text, "C:\\Users\\USER\\Documents\\Visual Studio 2015\\Projects\\ConsoleApplication8\\text.txt", "r");

if (text == NULL) {
    printf("Failed to open file\n");
    return (-1);
}

while (!feof(text))
{
    fscanf_s(text, "%s", string);
    if (!strcmp(string, input));
    num++;
}

printf("we found the word %d times\n", num);

return 0;
}`

Remove the `\n` from `scanf_s()` call. Also, see: [Why is “while ( !feof (file) )” always wrong?](http://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong) — P.P, Nov 06 '16 at 13:14
for `scanf_s()` while scanning `char` or `char*` you need to send a 3rd argument to specify the buffer length see here: https://msdn.microsoft.com/en-us/library/w40768et.aspx — Cherubim, Nov 06 '16 at 13:19
scanf is not suitable when learning C. Avoid it like the plague. — William Pursell, Nov 06 '16 at 13:34
@WilliamPursell - drop "when learning C" and we're in 100% agreement. :-) — Bob Jarvis - Reinstate Monica, Nov 06 '16 at 13:36
@Bob Jarvis, I was going to write "once you've learned c, you won't need it", but didn't want to seem too extreme. I truly don't understand why people teach it! — William Pursell, Nov 06 '16 at 13:37

score 1 · Answer 1 · edited May 23 '17 at 10:31

[From this "C:\\Users\\USER\\Documents\\Visual Studio 2015\\ ... I concluded the compiler in use is MS-VC]

Besides the wrong use of feof() as pointed out by MarianD in this answer, there is the following fatal mistake:

This line misses the size of the buffer to scan into:

  fscanf_s(text, "%s", string);

It should be

  fscanf_s(text, "%s", string, (unsigned) sizeof string);

Same plus 1 issue here:

  scanf_s("%s\n", &input)

Pass input, not its address. %s expects a char* (to which input decays). Doing &input would in fact pass the same value, but use the wrong type, namely char(*)[20], which would invoke UB.

Pass its size:

scanf_s("%s\n", input, (unsigned) sizeof input)

From fscanf_s documentation:

The main difference between the more secure functions (that have the _s suffix) and the other versions is that the more secure functions require the size in characters of each c, C, s, S, and [ type field to be passed as an argument immediately following the variable.

[...]

The size parameter is of type unsigned, not size_t.

score 0 · Answer 2 · edited Nov 06 '16 at 16:58

0

change

scanf_s("%s\n", &input);

by

scanf_s("%s\n", input);

Indeed input is already a char* and you are sending a char (*)[20].

edited Nov 06 '16 at 16:58

alk

66,653
10
83
219

answered Nov 06 '16 at 13:20

Glick

121
7

**No, you are wrong** (in spite the idea behind it is in general true). `input` and `&input` are in this case the same - see [How come an array's address is equal to its value in C?](http://stackoverflow.com/a/2528328/7023590) – MarianD Nov 06 '16 at 14:30
Hmm, maybe that's because you are not compiling with the same flags as me but if you try with -pedantic -Wall flag you'll get a warning. – Glick Nov 06 '16 at 14:43
It is only **warning** (incompatible pointer type) as compiler don't know anything about **using** this in the body of the called function (particularly if it will perform *pointer arithmetic* - which **is** different for `input` and `&input`). **Values** (= addresses) are the same, **behavior** is **in this case** the same, too, so **your answer has no chance to solve** the problem. (**I'am sorry** that you are not correct but is it not pleasurable to learn something new?) – MarianD Nov 06 '16 at 15:42
2

@MarianD: Same value but wrong type, so using `&input` invokes UB by passing the wrong pointer type, namely `char(*)[20]` instead of `char*`. – alk Nov 06 '16 at 16:42
1

Assuming MS-VC, this `scanf_s("%s\n", input);` is incomplete, to not say wrong. – alk Nov 06 '16 at 16:59
I agree with you (2 times) but my point was that in this case it doesn't make a difference of behavior (and so it doesn't help the person who asked this question). – MarianD Nov 06 '16 at 17:03

How to search for the number of times a word appears in a text file

2 Answers2