Thread: Working with char

This simple section of my program isn't working as I expected.

Code:

printf("Make a move (A,B,L,R): ");
move = getchar();
printf("\n move = %c\n", move);

It never actually wait for me to enter a character, why is this so?

getchar gets a character from the keyboard buffer. If you've already got input in the keyboard buffer waiting for it, then it's not going to hang around waiting for more.

Sorry but keyboard buffer? I'm not sure what that is.
The ASCII being returned is actually -1, which isn't appearing on that chart. Ok so I should do something like

Code:

while ( (getchar() == -1) && (getchar() == '\n') && (getchar() == ' ") ) {
    move = getchar();
}

In order to avoid this -1 thing, any new lines and spaces.

That means you have bigger problems. What are you typing right before this code (if anything)? Are you redirecting input from a file? Context.

Yes it's input from a file, but it could also equivalently be input from the user. If there are any other questions you need answering, just ask. I'd post the code too but it's about 300 lines long so I doubt you want to see all that.

Ok so I'm not getting an ascii of -1 anymore, but it keeps posting 32 (space) when I use a file input:

Code:

char makeMove() {
    char move = ' ';
    
    printf("Make a move (A,B,L,R): ");
    while ( (getchar() == -1) && (getchar() == '\n') && (getchar() == ' ') ) {
        move = getchar();
    }
    printf("\n move = %c (ascii %d)\n", move, move);
    
    return move;
}

So how could I get it to actually read the input from the user? Oh by the way, when I enter the file in manually through the prompt, it actually stops to wait for my input but it still says that the char move variable is different to what I entered.

If you're redirecting input from a file, that is:

Code:

myprog < input

then you can't also get input from the user. -1 would correspond to EOF which would mean that your file is empty.
Also your while statement is a very interesting thing, and I doubt that it's quite what you want. For instance, if the first getchar is anything at all, then move is never changed (because you never assigned the getchar result to move), so it is still the space you set it to be at the very top.

So

Code:

move = getchar();

is completely ignored? Maybe I should be using scanf instead then.

Originally Posted by Mentallic

So

Code:

move = getchar();

is completely ignored? Maybe I should be using scanf instead then.

It's completely ignored only because you surrounded it with a while loop that cannot possibly actually run (since the loop condition must needs be false). Perhaps you meant something like

Code:

move = getchar();
while (move == '\n' || move == ' ')
    move = getchar();

(Note the assigning of move so that the character is actually read, plus the change in the while loop to make it at least feasibly a loop.)

Oh that makes perfect sense! Thankyou for your help.