C: Convert char to float

Question

I want to convert a char to a float in language C. But atof() and strtof() are not working.

Here is some code, maybe someone could help me! The difficulty is that my number has a e-02 included

char temp = "6.345e-02"; // the original value is read from a file
float result;

result = atof(temp); //not working correct
result = strtof(temp, NULL); //also not working correct

edit: new code

FILE *file = fopen("file.txt", "r");
char c;
char *temp[11];
float result;
while((c=fgetc(file))!=EOF){
  if(c=='\t'){
    result = atof(temp); //here is the converting problem
    printf("%.6f\n", result);
  } else {
    temp[i] = c;
  }
}

Read compiler warnings. Any C compiler must give you an error or warning message for this code. If yours doesn't, uninstall the crap. — Lundin, Mar 11 '19 at 14:26
Terminating your `temp` string you must... And initialize `i` to 0 first... Also: `fgetc` returns an `int`, not a `char`. — Gerhardh, Mar 11 '19 at 14:35
The "new code" is nothing like the "original" one. Please, *always* provide [mcve] in the future (you still haven't provided one by the way..). — Eugene Sh., Mar 11 '19 at 14:36
You changed your code again. Please avoid creating a moving target. No one wants to waste time for an answer that is useless after the next change. And please provided the output you get. Together with minimum **complete** example. — Gerhardh, Mar 11 '19 at 14:45
[`getchar` returns an **`int`**](https://stackoverflow.com/q/35356322/918959) — Antti Haapala -- Слава Україні, Mar 11 '19 at 14:49

score 1 · Answer 1 · answered Mar 11 '19 at 14:24

1

You're declaring temp as a single character which is not. It's a character array so it must be declared as char *temp instead.

answered Mar 11 '19 at 14:24

Ahmed Karaman

523
3
12

Question has changed, the answer is no longer valid. – Jabberwocky Mar 11 '19 at 14:37
2

@Jabberwocky which is actually the problem of the question... – Eugene Sh. Mar 11 '19 at 14:37

abelenky · Answer 2 · 2019-03-11T14:39:27.577

1

I ran this on IDEOne, and found that if I don't #include <stdlib.h>, I got incorrect results

#include <stdio.h>
//#include <stdlib.h>            // <== This line is crucial

int main(void) {
    char* temp   = "6.345e-2";
    float result = atof(temp);

    printf("%f\n", result);

    return 0;
}

With `stdlib.h:`

Success #stdin #stdout 0s 9424KB
0.063450

Without `stdlib.h`:

Success #stdin #stdout 0s 9424KB
0.000000

edited Mar 11 '19 at 14:39

answered Mar 11 '19 at 14:33

abelenky

63,815
23
109
159

Question has changed, the answer is no longer valid. – Jabberwocky Mar 11 '19 at 14:37

C: Convert char to float

2 Answers2

With stdlib.h:

Without stdlib.h:

With `stdlib.h:`

Without `stdlib.h`: