Re: trapping key press using signals

["Bharti" <bhartig@sasken.com>]

Hi,

       With reference to your question : How to catch signals generated by 
key press using signals i would like to share a piece of code which will 
help you understand  the concept more easily.

There are basically 3 ways to send singnals to Processes:
1.Using the keyboard : Like Ctrl-C , this causes the system to send an INT 
signal (SIGINT) to the running process by default it causes the process to 
immediately  terminate. Another one is Ctrl-Z  (SIGTSTP) which causes the 
process to suspend execution and Ctrl-\ (SIGABRT) which does the same as 
Ctrl-C but gives us some better flexibility.
Here is the piece of code snippet that causes the progeam to print the 
string "Testing Code to understand" when a user presses Ctrl-C:

#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<signal.h>
void catch_int(sig_num)
{
   /* re-set the signal handler again to catch_int, for next time*/
signal(SIGINT,catch_int);
printf("Testing Code to understand\n");
fflush(stdout);
}

int main(int argc,char* argv[])
{
/*set the INT (Ctrl-C) signal handler to 'catch_int' */
signal(SIGINT,catch_int);
/*now,lets get into an infinite loop of doing nothing.*/
for(;;)
     pause();
}

The pause() system call causes the process to halt execution, until a signal 
is received. It is suerly  better than a 'busy wait' infinite loop.


2. Sending signals from the command Line: Like Kill
 kill-<signal><PID>
If no signal name or number is specified, by default TERM signal is sent to 
the process.
3. Using Susyem Calls:  This way of generating signals is acheived by using 
Kill system call (normal of sending a signal from one process to another).

Bye,
Bharti.

"pdn" <preetham@sasken.com> wrote in message 
news:ds7ggl$jc4$1@ncc-m.sasken.com...
> Hi,
>        How do i catch the signals generated by keypress using signals.
>
> 



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