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Top Forums Shell Programming and Scripting Alternative network messaging? Post 302721441 by Corona688 on Thursday 25th of October 2012 11:49:48 AM
Old 10-25-2012
A signal is a way to tell a program to do something when told instead of constantly checking for something. If it hasn't been told to do anything when it gets the signal, the signal will probably kill it instead.

Code:
#!/bin/sh

# Display the contents of a file and set a variable on SIGINT
trap 'cat /tmp/filename ; rm /tmp/filename ; VAR=1' INT

echo "My PID is $$"

while true
do
        VAR=0
        # Two reason read might fail -- end of file, or SIGINT.
        # If it was interrupted, just try again.  Otherwise, quit.
        if ! read LINE
        then
                [ "$VAR" -eq 1 ] && continue
                break
        fi

        echo "read line from keyboard: $LINE"
done

Run this in one window:
Code:
$ ./stupidchat.sh

My pid is 21188

Then do this in another:

Code:
# Vitally important message
$ echo "hey guys alj af MY FACE IS A ROTTORN BANANA" >/tmp/filename
$ kill -INT 21188

...and the first script should receive the signal, trap it, read the file and delete it

Last edited by Corona688; 10-25-2012 at 01:09 PM..
This User Gave Thanks to Corona688 For This Post:
 

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IFSERVICES(5)						       Network configuration						     IFSERVICES(5)

NAME
ifservices-* - control network services with ifup/down SYNOPSIS
/etc/sysconfig/network/ifservices-<configuration_name>/ DESCRIPTION
The directory /etc/sysconfig/network/ifservices-<configuration_name>/ is read by the script /etc/sysconfig/network/scripts/ifup-services which starts and stops system services when an interface is set up/down. ifup-services is used by /sbin/ifup, which is the command line user interface for setting up network interfaces. This is useful if you don't have a permanent network connection. If you sometimes boot without network and plug in the network cable later you can add links to system services in this directory. These services will then be started with ifup and stopped with ifdown. The configuration name used for ifservices-* should match exactly the configuration name of the ifcfg-* file for the interface. For the usage with NetworkManager (where you don't necessarily need a ifcfg-* file) you can also use /etc/sysconfig/network/ifser- vices-<interface>-<essid>/ (for wlan interfaces) or if that does not exist /etc/sysconfig/network/ifservices-<interface>/. As a final fallback /etc/sysconfig/network/ifservices/ is checked as well. If NetworkManager is active services will be stopped after the interface is down. The links in this directory are equal to the links in the runlevel directories /etc/init.d/rc*.d/ They have to point to service start scripts which are usually in /etc/init.d/. Links starting with 'S' are start links, which are called in alphabetical order after ifup has set up the interface. Links starting with 'K' are kill links which are called before ifdown takes down the interface. See also section Sequencing Directories in boot (7). EXAMPLE
In this example we use an interface with MAC address 00:de:ad:be:af:00. This interface is not always physically connected. As soon as you plug in the cable ypbind and autofs should be started. When you pull the cable they should be stopped. This can be reached with: in file /etc/sysconfig/network/ifcfg-eth-id-00:de:ad:be:af:00 ... STARTMODE=ifplugd ... in dir /etc/sysconfig/network/ifservices-eth-id-00:de:ad:be:af:00/ S10portmap -> /etc/init.d/portmap S20ypbind -> /etc/init.d/ypbind S30autofs -> /etc/init.d/autofs S20autofs -> /etc/init.d/autofs K30ypbind -> /etc/init.d/ypbind Now you have to disable the start of this services at boot time chkconfig ypbind off chkconfig autofs off Notes: You may call scripts/create-ifservices-directory [<interface_name>] to create a directory with the links from this example. This will cre- ate the directory ifservices-<interface_name> or if no interface name was given ifservices-template. Maybe you have to add also variable IFPLUGD_PRIORITY. For details about startmode ifplugd read ifup (8). The service portmap had to be added because ypbind needs it. This service is still started at boot time because it does not need an active network connection. But ypbind may now be started earlier as usual. Therefore we make sure that portmap is started before. Starting an already running service again does not affect the service. SEE ALSO
ifup(8), ifcfg(5). AUTHOR
Christian Zoz <zoz@suse.de> sysconfig February 2005 IFSERVICES(5)
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