I'm trying to alphabetically sort my argv[] array, which will hold char pointers(strings) from the command line. This is my code, but it doesn't seem to be doing anything. Anyone see whats wrong?
Code:int sort_function( const char *a, const char *b) //this is the actual compare function! { return(strcmp(a,b)); } int main (int argc, char *argv[]) { qsort(argv, sizeof(argv), sizeof(argv[0]), sort_function); for (x = 1; x < 4; x++) printf("%s\n", argv[x]); }
Last edited by serg_yegi; 03-27-2010 at 05:32 PM.
sizeof(argv) is almost certainly 4 irrespective of how many things you actually have. argc will tell you how many things you need to sort.
Do I need to assign qsort to something, because even with the argc replacement, I get the same incorrect results.
qsort returns void, so there's nothing there. I am (suprisingly to me at least) getting utter meaninglessness when I print the strings inside the comparator:
More details if and when I figure something out.Code:>temp this that a and b Called with string 39♥ and -9♥, returning 1 Called with string 99♥ and 39♥, returning 1 Called with string ?9♥ and 99♥, returning 1 Called with string B9♥ and ?9♥, returning 1 Called with string G9♥ and B9♥, returning 1 Called with string 39♥ and -9♥, returning 1 Called with string 99♥ and 39♥, returning 1 Called with string ?9♥ and 99♥, returning 1 Called with string B9♥ and ?9♥, returning 1 Called with string 39♥ and -9♥, returning 1 Called with string 99♥ and 39♥, returning 1 Called with string ?9♥ and 99♥, returning 1 Called with string 39♥ and -9♥, returning 1 Called with string 99♥ and 39♥, returning 1 Called with string 39♥ and -9♥, returning 1 this that a and b
Okay after printing absolutely everything out, I was reminded of what I failed to parse from the description of qsort:
(emphasis mine)Originally Posted by ISO C standard
so what your comparator receives are two void *, which point to the data and are therefore functionally char **. So your comparator should look like
You're going to get warnings about dumping the const, which you can fix or ignore at your discretion.Code:int sort_function( const void *a, const void *b) //this is the actual compare function! { char **first = a; char **second = b; return(strcmp(*first,*second)); }
(You'll also want to be careful, when sorting, not to mix the name of the program at argv[0] into the mix as well.)
Thanks a lot. Is there anyway you can top me on how to avoid argv[0]? Everything I've tried so far has produced errors.
Start sorting with argv[1].
Nevermind, got it. Thanks for the help.
