Checking User Input

**Dusterdoo** · 06-25-2011

I'm working on a simple windows application that loads and reads text from a file. I've already gotten the loading and printing code written. But, I'm at a little bit of a hangup, being that I'm new to programming in C. What I would like help on is adding sort of a "command" to my program. IE: If the player types the word "read" into the console, then the application loads the text file, and prints it.

Thanks, Dusterdoo.

**whiteflags** · 06-25-2011

Do you know how to call fgets and compare strings with strcmp? That would be a start.

**Dusterdoo** · 06-25-2011

I've heard of it, but the book I'm reading doesn't give much help on what I'm trying to do.

**tabstop** · 06-25-2011

Generally speaking, you're not going to find "exactly what I'm trying to do" in a book. You're going to find all the tools you'll need; your book (or other tutorials) will tell you how to use fgets and strcmp. The point is, they'll teach you how to use them for everything, not just for this one particular application. So use your book to find out what fgets and strcmp do, and then you should have some idea as to how to use them to do what you want.

**Dusterdoo** · 06-25-2011

Let me rephrase. The book I'm reading doesn't really explain fgets and strcmp at all. It just shows you an example program with only a couple comments.

**tabstop** · 06-25-2011

Well, this looks pretty reasonable: fgets - Wikipedia, the free encyclopedia strcmp - Wikipedia, the free encyclopedia

**smokeyangel** · 06-25-2011

Shouldn't be too difficult, based on what you say you've done already. Reading from the command prompt is just like reading from a file.

I guess your code is something like

Code:

int main(void)
{
   .... read file and print it
}

So you just slot options reading in before you do anything else. I'd structure it like:

Code:

int main(void)
{
     buffer[MAX_STRING_LENGTH];
     while (fgets(buffer, MAX_STRING_LENGTH, stdin))  // this will stop when EOF is detected. EOF is Ctrl+Z on windows. you might want to accept an 'exit' command as well (see below).
    {
         if (strcpy(buffer, "read") == 0)
             .... read file and print it
         else if (strcpy(buffer, "exit") == 0)
              break;  // exit while loop.
                 
    }


}

Hope that helps.

**~~CommonTater~~** · 06-25-2011

Originally Posted by Dusterdoo

Let me rephrase. The book I'm reading doesn't really explain fgets and strcmp at all. It just shows you an example program with only a couple comments.

The compiler you're using should include documentation of it's library functions (If it doesn't, get a different one), so it's mostly a matter of (GULP) ... are you ready for this.... Reading the help files.

**AndrewHunter** · 06-25-2011

Originally Posted by smokeyangel

...

Code:

...     
    while (gets(buffer))  // this will stop when EOF is detected. EOF is Ctrl+Z on windows. you might want to accept an 'exit' command as well (see below).
    {
         if (strcpy(buffer, "read") == 0)
             .... read file and print it
         else if (strcpy(buffer, "exit") == 0)
              break;  // exit while loop.
                 
    }


}

All very valid and useful suggestions. One minor correction is to try to avoid using gets() if at all possible. You can read why gets() is bad.

**smokeyangel** · 06-25-2011

Thanks - of course, you're right. I've edited my previous post to use fgets.

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