Interacting with the linux console

[manasij7479]

#This may not be the conceptually right place for this post, but I'm hoping for a solution which is a little portable( and wouldn't have to be changed with ..say..changing kernels..or using another flavour of unix) and is C++ friendly.#

Using the system command lets the user 'send' a command to the console and (as far as I know)..that is all , nothing more.

But suppose I want to implement a program which has to give a shell command, get back the response of the console in a string (when the console prompts for input)...and repeat the process.

What would be the best( or 'only' ) way to do so ?

[cyberfish]

For one-way communication look up popen().

For bi-directional communication it gets quite a bit more complicated.
exec
would be a starting point.

[manasij7479]

I was hoping for something simpler..!..but after going through that ..I'm almost sure that a simpler solution does not exist.

[new_ink2001]

Manasij,

Paul S. Wang mentioned another facility in his Introduction to ANSI C on UNIX (ISBN: 0-534-14232-X) there about page 370.
>> A pipe is a direct (in memory) I/O channel between processes.
>> ...
>> The pipe can be thought of as a first-in-first-out character buffer (Figure 12.3) with
>> a read descriptor pointing to one end and a write descriptor pointing to
>> the other end.
>> To establish a pipe, use the system call

>> int pipe(int fildes[2])

>> to obtain a buffer and two descriptors...

I believe that the operating system (Linux specifically) will report that there is a pipe (I think it calls it a message queue these days) via the ipcs command. Wang's usage involves using fork to generate multiple processes and applying the pipe so that they may communicate directly. Here is a code fragment which he suggested:

int fildes[2];
...
   pipe(fildes);   /* establish message queue with operating system */

   if( fork() == 0 )
   {
      close(fildes[1]);   /* child reads fildes[0] */
      ...
      _exit(0);
   }
   close(filedes[0]);   /* parent writes fildes[1] */

He gets more elaborate latter using pairs of pipes so that the children can communicate bi-directionally with the parent process.

Best Regards,