shell script timing

rockarolla · 12-26-2006, 03:13 AM

Hi,

how can we run a given shell script or application at a given time, say once or periodically?

thanks!

penguiniator · 12-26-2006, 03:23 AM

To run it once use the at command. You must ensure that the at daemon is running. Then you can type something like:

at 4:07pm
warning: commands will be executed using /bin/sh
at> command to run
at> another command to run
at> Ctrl+d
job 1 at 2006-12-26 04:07
$

You can place this in a script to make it reschedule itself like this, perhaps using calculated times based on runtime conditions:

at $time 2>/dev/null << EOF
command to run
another command to run
EOF

You can also use cron to create a regular schedule for the program.

leo.zhai · 12-30-2006, 01:29 AM

You can use "crontab -e" to edit a regular schedule and use "crontab -l" to display your schedule.

rockarolla · 01-01-2007, 08:46 AM

actually what I need is to listen to a given process or event that is due to certain circumstances my desktop is connected via a linksys usb adapter WUSB54G but the connection is not stable and from time to time its disconnected. I need to reconnect manually or as I did using the cron facility, However the latter cannot add a modprobe as I think the path is not correct. The disadvantage cron has is that even if the connection isn't broken it will periodically run the commands (like ifconfig wlan0 etc...) I think it is possible to make it better by adding a line in the /etc/inittab file for example using respawn when the connection is lost ld you suggest a better way?

thanx,

FredrikN · 01-06-2007, 06:11 AM

Well, of of many ways is to create a script that autostarts everytime the systems turns on.

PHP Code:



#!/bin/sh

Create an array of ten sites or more.
ARRAY=(
  site1
  site2
  .. 
  ..
  ..
}

while [ true ]
do 
   Select a random site.
   RANGE=${#ARRAY[*]}
   number=$RANDOM
   let "number %= $RANGE"

   if [ `wget -O /tmp/trash.html ${ARRAY[$number]}` == TIMEOUT ]
   then 
       create a new connection
   fi

sleep 60;

done;

Or if you want to check if some process is alive

PHP Code:



#!/bin/bash

while [ true ]
do

 if [ "`ps aux | grep your_proc | grep -v grep`" == "" ]
 then
    echo 'Not alive, create connection or run some command'
 fi

sleep 60;

done;