how to read in octal

I am creating a simple calculator to do simple math in dec hex and octal froms , i am having trouble reading in an argument as a octal value, my hex is working fine when I enter 0x before the number but when reading in 010 for 8 in octal it just reads in 10, any suggestions?

Code:

#include<stdio.h>
#include <stdlib.h>
#include<string.h>
int main(int argc, char *argv[]){
  int a;
  int b;
  int c;
  int i;


  if  (argc  == 4 || (strcmp (argv[4], "dec") == 0 )){
    if (strcmp (argv[2], "+") == 0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a+b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "-")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a-b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "*")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a*b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "/")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a/b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "%")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a%b;
      printf("%d\n", c);}}

  if (argc == 5){
 if  ((strcmp (argv[4], "oct") == 0 )){
    if (strcmp (argv[2], "+") == 0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c=a+b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "-")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a-b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "*")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a*b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "/")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a/b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "%")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a%b;
      printf("%o\n", c);}}

 if  ((strcmp (argv[4], "hex") == 0 )){
   if (strcmp (argv[2], "+") == 0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c=a+b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "-")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a-b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "*")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a*b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "/")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a/b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "%")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a%b;
     printf("%x\n", c);}}
  }

return 0;
}

thanks

Read it as a string and parse from there. Scanf doesn't support octal(AFAIK) and it isn't too hard to convert anyway.

Originally Posted by User Name:

Read it as a string and parse from there. Scanf doesn't support octal(AFAIK) and it isn't too hard to convert anyway.

im not using scanf, we were told not to i am reading them in as arguments

Sorry, didn't RTFS.

Okay... The problem is with atof. You'll have to implement your own I guess. For octal:

Code:

int octal(char *num)
{
     int total = 0;
     for(int digit = 0;num[digit] != '\0';digit++)
          total += (num[digit] - '0') * (int)pow(8, strlen(num) - (digit + 1));

     return total;
}

Is your class at a point where this would be reasonable, or is this "too advanced" and they are likely looking for something else?

Originally Posted by User Name:

Sorry, didn't RTFS.

Okay... The problem is with atof. You'll have to implement your own I guess. For octal:

Code:

int octal(char *num)
{
     int total = 0;
     for(int digit = 0;num[digit] != '\0';digit++)
          total += (num[digit] - '0') * (int)pow(8, strlen(num) - (digit + 1));

     return total;
}

Is your class at a point where this would be reasonable, or is this "too advanced" and they are likely looking for something else?

sounds a little complicated but not aweful, is there no simpler way?

>> Scanf doesn't support octal(AFAIK)

Use %o -- see this page for a source.

> im not using scanf, we were told not to i am reading them in as arguments
So use sscanf() then.

Why ARE you using atof() when you should have used atoi()? Which should have done the octal magic for you.
Floating point doesn't do bases very well.

If you really want to make it robust, then use strtol().