[ale] re: timeout for read

[Eric Z. Ayers]

Geoffrey Myers writes:
 > }Is there any shell command in bash that will allow me to grab keystrokes other
 > }than read.  I would like to do a read command but give a time limit of 
 > }60 seconds.  Ne1 know how.  Or does ne1 have a C program that will take
 > }the time length on the command line and return the input on STDOUT?
 > 
 > I would think it would be pretty straight forward in C to fork and exec
 > a process that is going to expect the input and the parent could have the
 > timer.  If the timer expires, the parent could signal the child to go away.
 > If the timer doesn't expire, the child takes the input and signals the
 > parent that it has input.  You could get real fancy with pipes between the
 > two processes for communication and passing info.  Really, choose your
 > favorite IPC...
 > 
 > }

Let's not go overboard here.

This little program mayb be all you need to get the job done.  
I couldn't find a bash command to call alarm(), but I know you can catch
signals in a bash shell.  A more sophisticated version might reset the
alarm when a keystroke is pressed.

When the program exits, you can test $? in your bash program to see
if something was really typed, or if the alarm went off.

-------------------

#include <signal.h>
#include <stdio.h>


void alarm_cb (int signum)
{
	/*fprintf (stderr, "ALARM\n");*/
	exit(1);
}

int main (int argc, char * argv)
{
	char inbuf[1024];

	signal (SIGALRM, alarm_cb);
	alarm(30);
	fgets(inbuf, sizeof(inbuf), stdin);
	puts(inbuf);
	return 0;
}
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