check exit status

[rubing]

Yo homeys.

 

I am a linux programming noob, greener than your lawn, although i do know php, so not a complete rube.  I  am hoping I can get some help on writing my first script.

 

I am using a blackberry to get internet on my laptop (tethering).  I am damn damn sick and damn damn infuriated at having to always type the commands manually.  So, I wrote the following script:

#!/bin/bash
bcharge
pppd call barry-sprint&

 

This works, but is not really robust.  First, I really need to be able to check whether or not bcharge finds a phone plugged in.  If it doesn't detect anything then i'd want to wait a couple secs and try again, before failing gracefully.  Well, you don't need to hear about all that.  Basically I just want to know how to check whether the phone is plugged in.  Is this what they call exit status??

 

[trq]

You can check the exit status of the last command executed by looking at the $? variable. 0 meens success, anything else is some sort of error. eg;

 

#!/bin/bash
bcharge
if [ "$?" -eq 0 ] ; then
  echo "bcharge successfull"
  pppd call barry-sprint &
fi

 

You can also chain commands together using && (and) or || (or). eg;

 

#!/bin/bash
bcharge && pppd call barry-sprint &

 

This will only execute pppd call barry-sprint & if bcharge is successfull.

 

As for whether or not bcharge finds a phone plugged in, the first thing I would do would be to manually look for it within your /dev directory.

[rubing]

Hey Thorpe!

 

How's the php 5.3 install working?

 

well, I changed that script to read as follows:

 

Script blacknet:

#!/bin/bash

#start bcharge up and send any output to the void

bcharge &> /dev/null

THERE=$?

echo "checking for phone..."

if [ $THERE -eq 0 ];

then

echo "yay, we found you're phone"

#kill any running instances of ppp, before starting it up

pkill ppp*

pppd call barry-sprint&

else

echo "boo, we didn't find jack"

#this needs to sleep and check again first

fi

 

It works, but it runs entirely in the background.  So that if I type blacknet.  I get returned to a prompt and then as commands get executed they pop up.  I would rather the program take away the prompt until its finished running.

[trq]

Remove the & from this line....

 

pppd call barry-sprint&

[rubing]

hmmm...this isn't quite doing what I want, b/c the prompt is not returned at the very end.  It just kind of hangs there saying:

 

/etc/ppp/ip-up finished

[trq]

You need to exit the script at the end. eg;

 

exit 0

[rubing]

That doesn't work either.  Is there a command to take away the command prompt??

[trq]

You can kill it by setting it to an empty string. Seems a hack though.

 

PS1=""

 

You might want to store the current prompt in a temp var so you can restore it when your done. eg;

 

TMP="$PS1"
PS1=""
## do your thing
PS1="$TMP"