Thread: Why does '*' not work? (switch function) [EASY]

Hello everyone! =) I need some help in this case:

Code:

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

potenzieren(float basis, int exponent){ 
    int i; 
    float ergebnis = basis; 
    for(i=1;i<=exponent;i++) 
        ergebnis*=basis; 
        return ergebnis; 
} 
main (int argc,char *argv[]){ 
if (argc==2){ 
    if  (strcmp(argv[1],"-help")||strcmp(argv[1],"--help")||strcmp(argv[1],"help")){ 
    /*showtooltip*/ 
    printf("You can use this programm to calculate simple formulas step  by step.\n Operators you can use are:\n'+'\t\t for addition\n'-'\t\t for  subtraction\n'*' \t\t for multiplying\n'/'\t\t for division\n'^'\t\t for  exponential formulas\n'from'\t\t to get the chance of\n\t\t getting [x]  right from [y]amount\n"); 
    } 
} 

if (argc<4){ 
    printf("Use calculator '[number] [operator] [number]' to get a  result!\n"); 
    exit(1); 
} 
float z; 
if (argc==4){ 
float x = atof(argv[1]); 
float y = atof(argv[3]); 
switch (argv[2][0]){ 
    case '+': 
            z=x+y; 
            break; 
    case '-': 
            z=x-y; 
            break; 
    case '/': 
            z=x/y; 
            break; 
    case '*' :        //42 = '*' ASCII 
            z=x*y; 
            break; 
    case '^': 
            z=potenzieren(x,y); 
            break; 
    default : printf("Wrong operator!\n"); 
                break; 
} 
printf("%s %s %s = %f \n",argv[1], argv[2], argv[3], z); 

} 
exit(0); 
} 

Everything works right, should only be a simple programm to make easy calculations... But multiplying will not work correctly. =(
I don't know why, I even tried entering 42 as binary code, but won't work...

Some help? =)
Greets

You're using * on the command line, so I think the shell is interpreting that as a wildcard, as shells are wont to do.

thanks for the answers!
Yeah... you're right it's a wildcard (i'm using ubuntu)
Like mentioned i could put it in a string, but is there a way to ignore those wildcards? a starting preference of the programm or something like that?

and when i add an '-' in front of the operator will it crash too?
ex.: ./calculator 5 -- 2
result = 3?
same for ./calculator 5 -* 2 (=10)
or will it be interpreted as an wildcard again?

Originally Posted by Ribbley

thanks for the answers!
Yeah... you're right it's a wildcard (i'm using ubuntu)
Like mentioned i could put it in a string, but is there a way to ignore those wildcards? a starting preference of the programm or something like that?

You could escape it like "\*" so the shell doesn't interpret it but passes it as is to the program.

Originally Posted by Ribbley

and when i add an '-' in front of the operator will it crash too?
ex.: ./calculator 5 -- 2
result = 3?

That simply depends on how well the command line parser is written.

Originally Posted by Ribbley

same for ./calculator 5 -* 2 (=10)
or will it be interpreted as an wildcard again?

It'll be interpreted first by the shell, that's why utilities like bc or dc perform such operations inside their own shell.

You could escape it.

./calculator 5 \* 3

This always works in bash.

okay thanks! seems to work with \*... so i have to add it to the help text - "use '\*' to avoid wildcard usage" or smth like that... thanks !!
I will look here more often for answers ;D