Rc.Local

Half_Elf · 06-02-2002, 02:32 AM

Can I put a little script that recall himself after a sleep time in my rc.local file or this will prevent my system from booting?

My script is very simple and should recall himself every 5min of sleep
If I put this in my rc.local, is my system will be able to boot or it will wait for the end of the script forever?

sakeeb · 06-02-2002, 02:55 AM

i think the it will stop your system from booting if you are using sleep command.

Half_Elf · 06-02-2002, 09:47 AM

arrr... ok
Is there are any other way to do?
Can I use something else instead of a sleep that will not stop my system? Or can I put it somewhere else?

acid_kewpie · 06-02-2002, 10:12 AM

put the scipt in a fiel and fork it into the background:

script &

that's how to solve your problem, but it's a very bad solution to a trivial task. you'd be better off setting a cron job or something similar.

trickykid · 06-02-2002, 11:39 AM

Yeah you don't necessarily need to put a script in the rc.local for this type of job if its not needed at boot time, you can actually have it anywhere you want, setup a cron job to run it whenever needed as acid said.

Half_Elf · 06-02-2002, 04:59 PM

Herm... What is cron job?
I want to put my script in my iptables script (or near it) because my Ispoften change my Ip but my iptables still use the old ip. The script check every 5min if my ip still the same or not, if not restart iptables, ip-updater,server etc.... (please do not tell me to use interface, It gives me other problems!)
So well... If I add something like ./script & to my rc.local, or in my iptables script, will it work? I fact I want this script to recall himself every 5 min, so I use a sleep command. If you know a better way to do please tell me

(Btw Acid sorry for the double post, I just tried to "export" my problem to another forum because it is not really about Slack but mostly about programming)

Half_Elf · 06-02-2002, 05:27 PM

herm that was a very bad idea...
If I start the script with & when it recall himself, it recall another script without closing the first one and another and another....

So I have now something like 150 process of this script running and the same number of -bash hehehehe

Anyone know a better way?

What if, instead of recalling the same script after the sleep time, I just ask my script to "go to" the first line? (what's the syntax of that btw?)

acid_kewpie · 06-02-2002, 05:44 PM

"Anyone know a better way?"

YES.

A
CRON
JOB

man cron.

jtshaw · 06-02-2002, 10:31 PM

You asked what cron is... it is a daemon for running tasks at certain times. It allows you to set up tasks that run automatically on certain time intervals. Thus its purpose is to allow you to do things like what you are attempting. Man contrab is a bettter place to look though, man cron might not exsist on your slackware system (I know it doesn't on mine).
There is a howto on cron.

Half_Elf · 06-02-2002, 10:56 PM

Thanx, jtshaw, I will look at this.

trickykid · 06-02-2002, 11:24 PM

Quote:

Originally posted by jtshaw
Man contrab is a bettter place to look though, man cron might not exsist on your slackware system (I know it doesn't on mine).

Yeah, man cron doesn't exist but it is:
man crontab to clear up anyone that might not realize that was a spelling mistake on jtshaw behalf.

jtshaw · 06-03-2002, 09:49 AM

....opps People keep telling me to read my own posts.....

crabboy · 06-04-2002, 08:47 PM

I'd suggest using cron, but here are starter scripts for either cron or a daemon script. These are just examples to get you started, they have not been tested. It's not a good idea to have a script call itself, as you probably figured out.

Daemon script run from rc.local like: ./testInterface &

Code:

#!/bin/sh

LAST_IP=""

while [ 1 ]; do
 
   IP=`ifconfig eth0 \
        | grep "inet addr" \
        | cut -d":" -f2 \
        | awk ' { print $1 }'`

   if [ "$IP" != "$LAST_IP" ]; then
      if [ "$LAST_IP" = "" ]; then
         LAST_IP=$IP
      else
         echo restart
         LAST_IP=""
      fi
   else
      LAST_IP=$IP
   fi
   sleep 300 
done

Code for a script run from Cron every x minutes:

Code:

#!/bin/sh

IP_FILE="/etc/lastip"

if [ -e $IP_FILE ]; then
   LAST_IP=`cat $IP_FILE`
fi

IP=`ifconfig eth0 \
     | grep "inet addr" \
     | cut -d":" -f2 \
     | awk ' { print $1 }'`

if [ "$IP" != "$LAST_IP" ]; then
   if [ "$LAST_IP" = "" ]; then
      echo $IP > $IP_FILE
   else
      # restart iptables
      rm $IP_FILE 
   fi
else
   echo $IP > $IP_FILE
fi

Half_Elf · 06-05-2002, 12:09 AM

Hum these script are really better than mine

Using a loop is a good idea too I will try it

but why THIS : [ "$IP" != "$LAST_IP" ]
I tried without the ! and it works...
and what is #!/bin/sh
I saw it often but I never found any explication about this useless comment.
It says the path of the script auto-run or something like that it is that right?

can I write something to check error msg too? this is not suppose to happen but if my DSL isn't connected when the script start it can't find the right interface so I want to ask my script to restart the dsl in this case.

acid_kewpie · 06-05-2002, 03:49 AM

!= means not equal to. so obiovusly just removing the ! will make it WRONG

#!/bin/sh defines the interpreter, normal shell in this case, could be perl or a load of others