Stdin question

[Johanson]

I've been trying to make my program get its input from a file instead of typing everything myself.
So I thought of using fprintf to write what I had in the file to the stdin, and I tought everytime scanf appeared in the code it would read what I wrote in stdin but the program worked as if nothing changed.
Is it possible to do what I want with stdin or is there another way?

[grumpy]

Instead of what you're doing, open your file (using fopen()) as an INPUT file, and replace your calls of scanf() with calls to fscanf(the_file, <rest of arguments>). Keep in mind that scanf(<arguments>) is functionally equivalent to fscanf(stdin, <arguments>);

[ssharish2005]

So I thought of using fprintf to write what I had in the file to the stdin

u cant do that. stdin is a standard pointer pointing to standard input stream. u get an error when u do that

ssharish2005

[Salem]

int main ( ) {
  char buff[BUFSIZ];
  while ( fgets( buff, sizeof buff, stdin ) != NULL ) {
    fputs( buff, stdout );
  }
  return 0;
}

If you run this program from the command line as
prog.exe
then you would just type stuff in.

Or you could run it like this, to get input from a file
prog.exe < input.txt

int main ( int argc, char *argv[] ) {
  char buff[BUFSIZ];
  FILE *fp = fopen( argv[1], "r" );
  while ( fgets( buff, sizeof buff, fp ) != NULL ) {
    fputs( buff, stdout );
  }
  return 0;
}

You could run this program as
prog.exe input.txt

By changing just a few lines, you can flexibly read input from either stdin or from a file. Once the line of input is in 'buff', you can do whatever you want to it, with whatever functions you like.

One advantage of sscanf() over scanf/fscanf is that it doesn't alter the state, so you can have several passes over the same buffer with sscanf().

A good example is getting the user to type in a date in a flexible format (12/13/06 or Dec-13), and figuring out which format they chose.

[Johanson]

I don't think I explained my problem well, because I think it is a bit more complex.
My program asks for a command from a user then uses a scanf to get the first letter and uses that letter as the variable for a switch.
Inside the switch the program uses several scanfs to get the needed information from the buffer.
What I want to do is a command that opens a file and execute the commands that are written in the file, with every command with \n in the end.
I hope I was clear enough :|

[quzah]

We're not going to write the whole damn thing for you. Get crackin' and produce your attempt.


Quzah.

[Salem]

> I hope I was clear enough
I thought I was - you should have no problem if you read the snippets of code I posted.

I mean, just replace fputs(buff,stdout) with decodeMyCommandLine(buff) and you're almost there.

[Johanson]

> I hope I was clear enough
I thought I was - you should have no problem if you read the snippets of code I posted.

I mean, just replace fputs(buff,stdout) with decodeMyCommandLine(buff) and you're almost there.

I guess I misunderstood your previous post. Now I understand that I have to copy what is in the file to a string and then get the information from the string.

I guess I'll have to do some changes to the way the program runs, but nothing major.

Thanks.