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help with a unix shell script

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Top Forums Shell Programming and Scripting help with a unix shell script
# 1  
Old 01-10-2009
help with a unix shell script
hi,

i have just started learning shell scripting...



i use fedora10 with linux kernel 2.6.27.9-159.fc10.i686

i m trying to make a shell script to check for my ppp0 connection every 1min

the logic i use is pretty simple...

i check if there is any ppp0 connection , using ifconfig....if ppp0 is active then i sleep for 60 seconds and recheck...if at any time ppp0 is dropped (because of my goddamn ISP!! Smilie ) then ifconfig will not mention it....and if it does not mention it...then i ll use the "ifup ppp0" command and try and reconnect ...

here is the script

Code:
i=0
for((i=2;i<100;i++))
do
if [ ifconfig | grep "ppp0" | wc -l -eq 1 ] then
echo already connected
fi
if [ ifconfig | grep "ppp0" | wc -l -eq 0 ] then 
echo not connected
echo trying to bring up ppp0
 ifup ppp0
fi
echo current ifconfig 
ifconfig ppp0
sleep 60
i=$($i-1)
done

when i run the script...i get the following error

Code:
./ipcheckup.sh: line 6: syntax error near unexpected token `fi'
./ipcheckup.sh: line 6: `fi'

i dont understand why?
# 2  
Old 01-10-2009
Quote:
Originally Posted by c_d
hi,
Code:
i=0
for((i=2;i<100;i++))


That is non-standard syntax. More portable is:

Code:
i=2
while [ $i -lt 100 ]
do
    : ....
    i=$(( $i + 1 ))
done

Quote:
Code:
do
if [ ifconfig | grep "ppp0" | wc -l -eq 1 ] then


You don't need the test command (a.k.a. '[') and wc, and you must separate then from if <list>:

Code:
if ifconfig | grep "ppp0"; then

# 3  
Old 01-10-2009
verifing connectivity with your isp
While your script will verify that your ppp0 connection is active, there is a better way to do it. In some cases ppp0 will still show up in the output of ifconfig but your network connectivity is non-existant.

What you should be checking is the ability to ping an ip#, popular choices for the ip# would be your ISP's nameserver. if the ping fails shutdown your ppp0 and restart it.

while true ; do
ping -c 1 nameserver_ip# || echo "restart ppp0" ;
sleep 60 ;
done


James Dickens
uadmin.blogspot.com
# 4  
Old 01-10-2009
thanks guys...i modified the script as recommended...Smilie

here is a modified version

Code:
while true
do
    if ifconfig | grep "ppp0" ; then 
         echo already connected...
         echo current ipaddress
         ifconfig ppp0 | head -2
         echo ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
         echo verifying connection...
         ping -c1 google.com > op
         cat op | head -1
         cat op | tail -2
         echo 
         echo
   else
         echo not connected
         echo trying to bring up ppp0
         ifup ppp0
   fi
   echo 
   echo 
   echo
   sleep 60
done

now....i m glad that its working...but, i dont understand why wc did not work out...
Last edited by c_d; 01-10-2009 at 11:39 PM..
# 5  
Old 01-11-2009
ok...i need help again...

this is my current code

Code:
while true
do
    if ifconfig | grep "ppp0" ; then 
        echo already connected...
        echo current ipaddress
        ifconfig ppp0 | head -2
        echo ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
        echo verifying connection...
        ping -c1 google.com > op
        cat op | head -1
        cat op | tail -2
        echo 
        echo
    else
        echo not connected
        echo trying to bring up ppp0
        ifup ppp0
    fi
    echo 
    echo 
    echo
    i=60
    while [ $i -ne 0 ]
    do
        echo -e "next check-up in $i sec \r"
        i=$(($i-1))
        sleep 1
    done
done

the output comes out like this...

Code:
[c_d@localhost scripts]$ ./ipcheckup.sh 
ppp0      Link encap:Point-to-Point Protocol  
already connected...
current ipaddress
ppp0      Link encap:Point-to-Point Protocol  
          inet addr:<my addy>  P-t-P:<my addy>  Mask:<my addy>
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
verifying connection...
PING google.com (74.125.45.100) 56(84) bytes of data.
1 packets transmitted, 1 received, 0% packet loss, time 340ms
rtt min/avg/max/mdev = 294.700/294.700/294.700/0.000 ms





next check-up in 60 sec 
next check-up in 59 sec 
next check-up in 58 sec 
^Z
[25]+  Stopped                 ./ipcheckup.sh

i thought \r was for carriage return....why isn't it working?

i want it to print "next check-up in 60 sec" and then overwrite that sentence with "next check-up in 59 sec" ...
i dont want it to list every second...60 through 0.
Last edited by c_d; 01-11-2009 at 12:08 AM.. Reason: removed my ip address...:D
# 6  
Old 01-11-2009
Quote:
Originally Posted by c_d
Code:
    i=60
    while [ $i -ne 0 ]
    do
        echo -e "next check-up in $i sec \r"

Code:
printf "next check-up in $i sec \r"

Quote:
Code:
        i=$(($i-1))
        sleep 1
    done
done

the output comes out like this...

Code:
...
next check-up in 60 sec 
next check-up in 59 sec 
next check-up in 58 sec

i thought \r was for carriage return....why isn't it working?

i want it to print "next check-up in 60 sec" and then overwrite that sentence with "next check-up in 59 sec" ...
i dont want it to list every second...60 through 0.

echo prints a newline at the end. Use printf.
# 7  
Old 01-11-2009
done....sorry to bother you....Smilie

it was supposed to be echo -en instead of echo -e

....searched the forum and found the answer...
Smilie
great forum you got here...

EDIT:

didn't notice your post cfajohnson,your post showed up after i posted mine... thanks for an alternative...gonna try and see that too...and try to notice the difference between the two...
thanks again...

and echo -en also works....
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