another for loop problem

[Rasher]

hi folks could someone guide me on this
ive written a program that prints a character array backwards, if i state the character array it works fine
insert

#include<stdio.h>
#include<string.h>
int main()
{
	char name[25]= "arther";
	int letters;

	letters = (int)strlen(name);

	for(name; letters>=0; letters--)
		{
			printf("%c",name[letters]);
		}
	return 0;
}

However... if i try and get the character array from the user it compiles but does not work??
include

#include<stdio.h>
#include<string.h>
int main()
{
	char name[25];
	int letters;

	printf("Please enter your name ");
	scanf_s("%s",name);

	letters = (int)strlen(name);

	for(name; letters>=0; letters--)
		{
			printf("%c",name[letters]);
		}
	return 0;
}

any pointers would be very grateful!

[MK27]

You did not say what you meant by "does not work", but here's one issue:

"MK27\n"
"\n72KM"

Also, you are the first person I have ever seen cast strlen() -- totally unnecessary.

And why does your for loop look like this:

for(name; letters>=0; letters--)

[Rasher]

Ok my bad when i compile the second lot of code it asks for your name then the program terminates it does not then print it backwards.
as for the (int)strlen(name) ive only done c for about a week and that was the way i was tought. Just the same as my for loop just the way we were shown as i understand the for(name; letters>=0; letters--) does not need to be there just the ;?

[Rasher]

ok it works now i used gets() instead of scanf although im still not too sure why scanf wouldnt work? i think its because scanf() stops processing at the first space so it wouldnt read both names, where gets() can read more than one word?
sorry i know my 1st example only showed one word but ive decided to use two. ie first name and last name

[MK27]

ok it works now i used gets() instead of scanf although im still not too sure why scanf wouldnt work? i think its because scanf() stops processing at the first space so it wouldnt read both names, where gets() can read more than one word?

No, scanf("%s") will include spaces (and newlines ).

The problem with your for loop is this:
for (one;two;three);
"one" is a statement executed before the loop iterates. Generally, it is used to set the value of a counter, eg. "i=0".

"name" (a predefined variable) by itself is a meaningless statement in this context. What the loop should look like is:

for(letters = strlen(name)-1; letters>=0; letters--);

The reason for the "-1" is that the last element of "name" will be '\0', which there is no point in printing that. Obviously, this replaces the previous strlen call.

Also, use fgets() and not gets() -- gets is unsafe (since you were using the "safer" scanf_s before). I've never used scanf_s (just scanf) so I suspect your problem is that it wants an additional parameter to indicate the length of name (for safety) but I dunno -- check your docs!

[Rasher]

Thanks the for loops are actually starting to make sense now, i thought i would have to declare the variable letters before the loop

I understand about the -1 being the terminating zero and now understand why there was no point in name; being in the loop.

I tried to use fgets and gets_s but the compiler said too few arguments to call so i have stuck with gets().

Thanks for the explanation.

If i use scanf my program only prints the first word backwards, when i use scanf_s my program doesnt print anything, how can i make scanf print both words or is that something im likely to come across when i do strings and arrays more indepth?

[tabstop]

Despite what MK says, scanf with %s will stop at spaces.

[Rasher]

Ok thanks thats what i thought