Please Help Me With Switch Statement Problem

[sammynoy]

Hello! So I'm working on a little personal project. I have been coding in C for around a month and a half, but this is not my first language so I am not a complet beginner in programing.

So onto my little problem. I made a small example of the problem.

#include <stdio.h>
#include <string.h>



int keep_running = 1; //To keep loops running

//Function Decl
void list();
void help();


int main()
{
  //Decl
  char input[81];   
    
 while( keep_running == 1) //Main Screen
 {
     printf("root@chips:~# ");     
     gets(input);
     
     switch(input)
     {
     case 'ls' : 
                 list();
                 break;
     case 'help' :
                 help();
                 break;
     default :
             printf("Unknown Command");
             break;
             
     }
             
     
             


} //while end
      
       
        
 } //Main end   
              

void list() 
{    
     printf("FILES LISTED\n");
}
void help()
{
     printf("HELP STUFF");
}

I'm using Dev-C++ 4.9.9.2 and I get error messages:

C:\Users\*\Documents\C Projects\main.cpp In function `int main()':

24 C:\Users\*\Documents\*\main.cpp switch quantity not an integer

26:11 C:\Users\*\Documents\*\main.cpp [Warning] multi-character character constant

29:11 C:\Users\*\Documents\*\main.cpp [Warning] multi-character character constant

Not sure if I should of wrote strcmp (input, "ls") != 1 insted of just 'ls'

Have I done something wrong? I tried using a if else statement but that did not go to well.

[laserlight]

A few things to note before I get to your problem:

• Avoid global variables: keep_running should be declared in the main function.
• This declares a function named list that takes an unspecified number of arguments:
  

  void list();

  Since you want the function to take no arguments, declare it with a single parameter of type void:
  

  void list(void);

• The gets function leaves you vulnerable to buffer overflow. One option is to use fgets instead, but keep in mind that fgets will store the newline character read if there is space.

I'm using Dev-C++ 4.9.9.2 and I get error messages:

C:\Users\*\Documents\C Projects\main.cpp In function `int main()':

24 C:\Users\*\Documents\*\main.cpp switch quantity not an integer

26:11 C:\Users\*\Documents\*\main.cpp [Warning] multi-character character constant

29:11 C:\Users\*\Documents\*\main.cpp [Warning] multi-character character constant

Not sure if I should of wrote strcmp (input, "ls") != 1 insted of just 'ls'

Have I done something wrong? I tried using a if else statement but that did not go to well.

Yes, you are doing something wrong. In C, a character constant is delimited by single quotes, e.g., 'a' is a character constant. A string constant is delimited by double quotes, e.g., "a" is a string constant. You used 'ls' and 'help', which are string constants, except that they have more than one character, hence the warnings about "multi-character character constant". I am not sure when it is appropriate to use these, but I am sure that it is wrong here.

What you should do is to ditch the switch. Use an if-else chain, comparing strings. To compare strings, use strcmp from <string.h>, keeping in mind that strcmp returns 0 when the strings match.

[sammynoy]

I switched to if else and it works, but I think I did it wrong because it gives weird outputs.

#include <stdio.h>
#include <string.h>





//Function Decl
void list();
void help();


int main()
{
  //Decl
  char input[81];  
  int keep_running = 1; //To keep loops running 
    
 while( keep_running == 1) //Main Screen
 {
     printf("root@chips:~# ");     
     gets(input);
     
     if ( strcmp (input, "ls") != 0)
     {
          list();
     }
     if ( strcmp (input, "help") != 0)
     {
          help();
     }
     else
     {
          printf("Unknown Command\n");
     }
             
     
             


} //while end
      
       
        
 } //Main end   
              

void list() 
{    
     printf("FILES LISTED\n");
}
void help()
{
     printf("HELP STUFF");
}

[laserlight]

You're comparing wrongly. It should be strcmp (input, "ls") == 0. Furthermore, you need the else for the first if statement too.

[sammynoy]

That solved it. Thanks for the help!

[zub]

Avoid gets! Use fgets. And you compare string with "help" even if it is "ls" already. Rewrited in my style:

while( 1 ) {
   printf("root@chips:~# ");     
   if( !fgets(input, sizeof(input), stdin) ) { break; }

   if( strcmp(input, "ls\n") == 0 ) {           // fgets does not delete '\n'. Alternatively,
        list();                                // use function chomp (you can find many open-source
   } else if( strcmp(input, "help\n") == 0 ) {  // variations in Internet or just write your own).
        help();
   } else {
        printf("Unknown Command\n");
   }

}

void crop_string(char* s)
{
    if( s = strpbrk(s, "\n\r") ) {
        *s = '\0';
    }
}