How to convert part of a character array to a integer variable in C

Question

I have a assignment in which I am supposed to take in a user's input in the form of:

double, char('C' for Celsius or 'F' for Fahrenheit)

and convert it into the other temp scale. To do this task, I wrote this program:

The Program

/*
  The purpose of these program is to convert a user's input and use it in a tempurate conversion programs.
  By Paramjot Singh

  Psuedocode:

  import all needed files

  ask for user's input.

  convert user's imput into 2 varibles: a double and a char

  if the char is 'c' convert the double to farinhiet
  if the char is 'c' convert the double to celius

  display the result.
*/

 #include <stdio.h>
 int main( )
 {
    char input[7];
    printf("Welcome to the Tempurate Conversion Enter a number followed by C or F, depending on if you what to convert a Celuis Temp to Farinheit or vice versa.");
    fgets(input, 7, stdin);
    /*if (in == 'C' || in == 'c') commnented out code
    {
        int f = 9 / 5 (inint + 32);
        printf("Input ", in, " Output: " f, " F");
    }
     else (inint == 'F' || inint == 'f')
    {
        int c = 5 / 9 (inint - 32);
        printf("Input ", in, " Output: " c, " C");
    }
     else 
    {
       printf("I told you to enter c or f. Restart the program.");
    } */

     /*to test what was entered*/
     printf(input);
     return 0;
}

My question is what would I do to convert part of the character array to a double.

What format is the input supposed to be? I'm assuming, e.g., "30F" but you didn't say. All of the suggestions so far assume that the input has a comma. — lurker
– lurker, Commented Aug 9, 2013 at 17:48
Blanket statements like "don't use scanf" without reasons or alternatives are not very useful. — hyde
– hyde, Commented Sep 23, 2014 at 5:34

JackCColeman · Accepted Answer · 2013-08-10 01:13:26Z

1

Per the printf statement:

printf("Welcome to the Tempurate Conversion Enter a number followed by C or F, depending on if you what to convert a Celuis Temp to Farinheit or vice versa.");

It looks like you expect the user to enter (for example): 23.5c

This implies a: scanf("%lf%c", &inDouble, &inChar); statement with NO intervening comma.` Note the change to the variable names.

Also, the tolower(inChar) will simplify some of your if logic.

Hope this helps.

edited Aug 10, 2013 at 1:13

answered Aug 9, 2013 at 23:12

JackCColeman

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8 Comments

user529758 Over a year ago

+1 but you forgot to mention that fgets() and strtod() should be used instead of scanf(). Also, why not inDouble, if we are scanning doubles?

JackCColeman Over a year ago

Will edit the variables name. There is nothing wrong with scanf() when used as directed.

JackCColeman Over a year ago

@H2CO3 i guess everyone can have an opinion, but it certainly is NOT deprecated and new programmers writing console i/o will always use it. So, we might as well teach them how to use it correctly.

user529758 Over a year ago

I never said it was deprecated!

nneonneo Over a year ago

@H2CO3: The first one isn't particularly surprising given that scanf was designed for field-separated data (use fgets for lines). %s overrunning your buffers is definitely a problem that is too easy to make, so I'll accept that.

|

Kninnug · Accepted Answer · 2013-08-09 17:48:01Z

0

Scan your input with sscanf:

sscanf(input, "%lf, %c", &inint, &in);

Edit: inint is a bit of a misleading name. You're supposed to read in a double, right?

edited Aug 9, 2013 at 17:48

answered Aug 9, 2013 at 17:42

Kninnug

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