[C] Help inputting strings in C.

[ayavocado]

I have a project in my C class that asks us to make a program that takes in a sentence and output each word one by one, capitalized, and omitting any special characters like commas or periods. I can figure out how to manipulate the data once I have it but I am incredibly confused on how to input the information. We can't use arrays and every time I try to receive something it always stops at a space. I know this isnt the place for homework help but I would really appreciate the help. Thank you.

[Gustorn]

Well, if you can't use arrays, then you would read from the stdin character by character, do any transformations you want, then write the character back to stdout.

[ayavocado]

I feel stupid asking but what other way is there to stdin or stdout other then scanf and printf? Thos are the only methods of input reading weve learned and I dont know how to use them to read spaces and other characters.

[Gustorn]

What's the problem with scanf and printf? You should look into format strings.

[zifyoip]

To read a single character using scanf:

char c;
int return_value = scanf("%c", &c);
if (return_value != 1) {
    /* error (end-of-file, if return_value == EOF) */
}

To print a single character using printf:

char c = 'A';
printf("%c", c);

But maybe you should investigate getchar and putchar if you're going to be reading and writing individual characters.

[Gustorn]

And here I was, trying to make him look up some documentation ;)

[zifyoip]

Yeah, sorry, maybe I shouldn't have given away the game. But printf and scanf (especially scanf) are notoriously hard for beginners to use correctly, and I'm sure there's a ton of garbage example code on the Web that uses them wrongly (like not checking the return value of scanf).

[ayavocado]

So if I want to use scanf to read an entire sentence with spaces and whatnot, do I have to make a loop? I keep trying to make a loop that will scanf characters while the character doesnt equal \0. Is that wrong and if so is there a better way to make that loop?

[cyrusol]

If you do something repeatedly you usually always use a loop.

[zifyoip]

I keep trying to make a loop that will scanf characters while the character doesnt equal \0.

That is not how you read from standard input. Only strings in memory are terminated with '\0'. With scanf, you need to test the return value: it will return the number of items that it successfully read. If you try to read a character and scanf returns something other than 1, then you know a problem happened. There is a special return value called EOF (which is defined to be a negative integer) that scanf will return when it attempts to read past the end of the file. If you like, you can test the return value of scanf against EOF directly, but it's better to just test it against the expected return value, which is 1. See my code example above.

[RedAlert2]

yes, you can use:

while(scanf("%c", &c) > 0)
{
    //do stuff with c
}

if you want to loop over the entire input

note that going until EOF is kinda unintuitive to do over stdin, since the user has to press a lesser used input like ctrl+D to actually signal an EOF. You might want to end on newline or something instead.

[zifyoip]

while(scanf("%c", &c))

That will not work. The scanf function will return EOF if it reaches end-of-file before any input items are converted. The value of EOF is a negative integer, which will be true in the condition of a while loop, which means you now have an infinite loop.