Thread: How to manipulate keyboard input in console

I'm making a C program that works as a bot on a text-mode web browser. The program navigates on web pages and reads stuff from them.

Since making a set of pipes for both reading and writing to and from the browser which my program calls, seems a bit challenging for me, I've come to the conclusion that one handy way of making this work is to, according to desired keys to be pressed, put stuff into stdin. In other words: I want to manipulate keyboard input without actually having to press the keys on the keyboard.

How do I do this?

I understand this may be quite dependent on the platform. However, I don't intend to distribute my program. I'm an Ubuntu user.



So to make the story easier, I want to have a function like the following example:

press_key(56);

where 56 would be either ascii or keycode. The program wouldn't know if it's me pressing a certain key on the keyboard or if I called the press_key function instead.

Thank you for your answer! This sounds easy and makes a lot of sense Even though I've done C programming for many years, I'm really new to the pipes. I would also appreciate it, if I could get a simple example code of just a few lines, which shows how to do this.


"then replace your program's stdin":

Should I use freopen here or something else?



Right now I have something like:

Code:

handle=popen("browser","r");

//initialize key sending connection to "browser"
//how?

while(...){

//send keys to "browser":
// write(..., string_of_keys, size);

while(fgets(string,100,handle)){
   // do something with the string received from "browser"
}

}

pclose(handle);

I'd also like to mention, that I've grabbed one example code from the internet, which does fork(); and execl(...); and then just uses printf(...); to send keys to the program. I've been able to freopen(...); stdout so that I can receive data from the executed program. However, this prevents me from printf()'ing to the console because it all goes to the executed program. I haven't been able to solve this problem. This is why I've figured it would be the easiest if I can popen(...); the browser in mode "r" and then somehow send the keys to it. Since this subject is new to me, I appreciate all help a lot.

Originally Posted by apawamajawa

I'm really new to the pipes. I would also appreciate it, if I could get a simple example code of just a few lines, which shows how to do this.

Alright, there are actually a few ways of doing this. I'll just give you some pseudo-code to get you started, since I don't actually have anything that does this lying around.

Code:

mkfifo(pipe_name, ...);

int id = fork();
if(id)
{
int fd = open(pipe_name, O_RDONLY);
close(STDIN);
dup2(fd, STDIN);
execv(...);
}

sleep(1); // wait for the sibling to open the FIFO

int fd = open(pipe_name, O_WRONLY);
write(fd, "Key press string here\n", ...); // this sends input to the sibling (which should now be your browser), and it doesn't know the difference

Of course, you'll need to do some error checking, fill in the blanks, etc.. But otherwise this should get you started.

Originally Posted by apawamajawa

"then replace your program's stdin":

Should I use freopen here or something else?

I suppose you could. Though, I had a FIFO in mind. See my example above.