Need to convert value to be taken as int/float from a file in c

Question

I have a txt file which has the following data:

I need to read the file in a C program line by line. But whatever method I use to read the file, I get the value as a string. I need to get the values as int and float types(depending on the values). Is there any way I can do this? Operating platform is linux.

There's no way to help you solve the problem without doing the problem for you if you don't show us what you're doing that doesn't work. — K Scott Piel, Apr 10 '13 at 14:49
I have tried with fgetc and fgets. The following answer solved the issue. — Harikrishnan, Apr 10 '13 at 15:12

Caladan · Accepted Answer · 2013-04-10T15:13:24.950

2

Use fscanf()

FILE* f = fopen(name, mode);
float d;
fscanf(f, "%f\n", &d);

But this will always give you floats (use %lf for doubles).

If you want to know what's the format read a line as a string and then use strtod() to try to read it as a int first and see how much of the string was used (if all, it's an int) and strtod() to read as a double.

edited Apr 10 '13 at 15:13

answered Apr 10 '13 at 14:50

Caladan

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"In the absence of a size modifier, the application shall ensure that the corresponding argument is a pointer to **float**." -- http://pubs.opengroup.org/onlinepubs/009695399/functions/fscanf.html – autistic Apr 10 '13 at 14:58
`"%f"` is the (or at least "a") correct format for a `double`. There is no format for a `float`, because if you attempt to pass a `float` to `printf`, it'll be promoted to `double` before `printf` receives it http://stackoverflow.com/questions/4264127/correct-format-specifier-for-double-in-printf/4264154#4264154 – MOHAMED Apr 10 '13 at 15:39

score 1 · Answer 2 · answered Apr 10 '13 at 14:52

1

If you want to read float numbers use fscanf with %f percent code

float var;

while (fscanf(yourfilepointer, "%f", &var) == 1)
{
    // do your stuff with your float var
}

answered Apr 10 '13 at 14:52

Davide Berra

6,387
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MOHAMED · Answer 3 · 2013-04-10T15:31:38.890

0

read the file line by line as a float X

If X == ((int) X) then it's an int

Else it's a float

float X;
int a;
while(fscanf(file, "%lf", X)>0) {

   if(X == ((int) X)) {
      a = ((int) X);
      printf("scanned value is integer: %d\n", a);
   } else {
      printf("scanned value is float: %lf\n", X);

   }

}

edited Apr 10 '13 at 15:31

answered Apr 10 '13 at 14:50

MOHAMED

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BLUEPIXY · Answer 4 · 2013-04-10T15:34:26.907

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

typedef union _num {
    long int integer;
    double floating;
} NumberU;

typedef struct _n {
    char type;
    NumberU data;
} Number;

int main() {
    FILE *fp;
    int c,i;
    char buff[16];
    Number num[10];

    fp=fopen("data.txt","r");
    for(c=0;c<10 && NULL!=fgets(buff,sizeof(buff),fp);){
        char *ck;
        long di;
        double dd;
        di=strtol(buff, &ck, 0);
        if(*ck == '\n'|| *ck == '\0'){
            num[c].type = 'i';
            num[c++].data.integer = di;
            continue;
        }
        dd=strtod(buff, &ck);
        if(*ck == '\n'|| *ck == '\0'){
            num[c].type = 'f';
            num[c++].data.floating = dd;
            continue;
        }
        fprintf(stderr, "error input:%s\n", buff);
    }
    fclose(fp);

    for(i=0;i<c;++i){
        if(num[i].type=='i')
            printf("%ld\n", num[i].data.integer);
        else if(num[i].type=='f')
            printf("%lf\n", num[i].data.floating);
    }

    return 0;
}

Need to convert value to be taken as int/float from a file in c

4 Answers4