reverse a word

[hope]

hello all,

please help me to understand the following code; it compile fine but the it gives the correct result only for a word of length =< 3. However if I comment out the statement printf("len = %d\n",len) it works fine for all inputs.

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

char *ptr;


  
int main(int args, char *argv[]){
       
 int len = strlen(argv[1]);
 //printf("len = %d\n",len);
 int j = len - 1, i;
 char ch[len];
         for( ptr=argv[1],i=0; i<len; i++,j--){         
                 
              ch[i]=*(ptr + j); 
              }
                          
                 printf(ch);
                 printf("\n");
             
      system("PAUSE"); 
      }

[matsp]

You probably want ch[len+1] and and then put ch[i] = '\0' after the reversing loop.

Of course, ch[len] is non-standard even for C99 compilers, so if you want to follow C standard coding, you'd have to either use a statically sized buffer [remember to check the length before copying], or call malloc to allocate a suitable size string space [don't forget the +1 for the terminating zero].

And

printf("%s\n", ch);

is probably a better solution, as you would get "interesting" results if the user inputs "d%" or some such [and the right combination of % in the input may even cause a crash]

--
Mats