I am using this code to print from text file but the program gives me "-1.#IND00"

Question

I have a problem. I am using this code to print from text file but the program gives me a different number -such as 11732408.000000- each time. However I don't get this problem when ex is integer.

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

int main() {
    char example[] ="123.12/456 ";
    double ex = atof(strtok(example, "/"));
    printf("%lf", ex);
    return 0;
}

Welcome to SO. Please provide examples of working and non-working input. — rtx13, Apr 12 '20 at 23:31
Please provide a [minimal verifiable example](https://stackoverflow.com/help/minimal-reproducible-example). That is, code that others can copy, run and reproduce the problem. Please ensure to include the exact input, expected result and actual result. — kaylum, Apr 12 '20 at 23:37
We can't run your code because it is incomplete. And we also don't know what is in your input file and so can't even check that the code is reading it correctly. And finally, you have given an incorrect output but we don't know what the expected correct output is. Please read the provided link on how to create a minimal verifiable example. — kaylum, Apr 12 '20 at 23:45
I need to get some numbers such as 44.5676. If I change from float to int I can get it but I need to get in double type. — aybkcn, Apr 12 '20 at 23:45
Yes, but what does the input file look like? How is `line` declared? How was the file read into `line`? What is the code before this? In programming, the details really matter alot. The error could be in any of those steps. Thus with so much missing detail we can't effectively help. — kaylum, Apr 12 '20 at 23:47
Thank you for your advice about a good question. This is my first question and English is not my native language so I may not have been able to explain my problem completely. I edited the question and elaborated it, I hope it is understandable. — aybkcn, Apr 12 '20 at 23:58
the posted code does not compile! it is missing a LOT, including the `#include` statements for the needed header files, a `main()` function AND the complete function that contains this code snippet — user3629249, Apr 13 '20 at 01:20
when using `strtok()`, always check (!=NULL) before trying to use the pointer returned by `strtok()` — user3629249, Apr 13 '20 at 01:21
the functions: `atoi()` and `atof()` do not step over leading spaces, so should be checking for that condition. The function `strtok()` tends to skip over multiple/adjacent 'delimiters` so should watch for that kind of 'oops'. Suggest (for debugging) to print each char array that is returned by `strtok()` so you will know exactly what is happening — user3629249, Apr 13 '20 at 01:31
[`atoi` shouldn't be used](https://stackoverflow.com/q/17710018/995714) (at least on non trusted input like files). Use `strtol` instead — phuclv, Apr 13 '20 at 02:25
Thanks for your comments. I edited the question by simplifying it, I hope you can help. — aybkcn, Apr 13 '20 at 07:16

score 0 · Answer 1 · answered Apr 13 '20 at 10:17

0

I could solve my problem. Thank you for your helps.

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

int main ()
{

    char example[20]  ="123.12/456 ";
    double ex=atof(strtok(example,"/"));
    printf("%lf",ex);




    return 0;
}

answered Apr 13 '20 at 10:17

aybkcn

25
4

chqrlie · Answer 2 · 2020-04-13T10:48:59.667

You forgot to include <stdlib.h> which contains the declaration of atof().

Your compiler is lenient and accepts your code is spite of the missing declaration, and it incorrectly infers the prototype to be int atof(char *), which causes undefined behavior when storing the return value to ex.

Hence the bogus output.

Note also that the l in the format %lf is necessary for scanf() but ignored by printf() as float arguments are implicitly converted to double when passed to vararg functions.

Here is a corrected version:

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

int main() {
    char example[] = "123.12/456 ";
    char *p = strtok(example, "/");
    if (p != NULL) {
       double ex = atof(p);
       printf("%f\n", ex);
    }
    return 0;
}

I am using this code to print from text file but the program gives me "-1.#IND00"

2 Answers2