Shell Programming and Scripting

Hello,

What I want to accomplish is this:
I have made a very simple script that runs 2 commands, polipo proxy and tor. The script runs successfully and the output of tor is visible to the screen.
I am using the trap command in order to catch the ctrl+c button combo in order to stop polipo (/usr/local/etc/rc.d/polipo stop). This does not work because, i think, tor catches the signal and exits gracefully and polipo stays running.

I think i have 2 solutions, neither of which i know how to implement:
1. The script runs tor in the "background" (if possible with visible tor output as it was), catches the SIGINT signal and executes the "/usr/local/etc/rc.d/polipo stop" command AND sends the SIGINT signal to the tor process as well, so both exit gracefully.

2. Both the script and the tor process catch the SIGINT signal and exit gracefully.

The script is this:

Code:

#!/bin/sh

echo "Initializing Tor..."

/usr/local/etc/rc.d/polipo onestart

# Start tor
tor

# catch ctrl^c to close polipo as well
trap '/usr/local/etc/rc.d/polipo stop' 2 15

I have 2 and 15 because i was testing what i mentioned above.
My shell is tcsh.

Thanks

If Tor is catching the SIGINT and exiting gracefully can't you just:

Code:

#!/bin/sh
echo "Initializing Tor..."
/usr/local/etc/rc.d/polipo onestart

# catch ctrl^c to close polipo as well
trap '/usr/local/etc/rc.d/polipo stop; quit' 2 15

# Start tor
tor
 
echo "Cleaning up Tor..."
/usr/local/etc/rc.d/polipo stop

It works , thank you very much.
The thing is that i do not know why it does. Just because you changed the order of the commands executed? I do not get why it works now and why it didnt in the first place... Would be grateful if you could explain

#!/bin/sh echo "Initializing Tor..." /usr/local/etc/rc.d/polipo onestart # catch ctrl^c to close polipo as well trap '/usr/local/etc/rc.d/polipo stop; quit' 2 15 # Start tor torThats the script im using, i do not stop polipo with another command

Thanks much anyway.

PS: the quit command is not necessary, i get a "command not found error", but the script does work

Yes the quit was a typo it should probably be something like exit 2, still it's good to know that your trap code is not executing. The exit is nice as it allows anything that calls this script to know if an interupt was trapped or not.


Things to note is that polipo is a background daemon (I assumed this because it's being started by an rc.d script). tor on the otherhand is running in the foreground control dosn't return to your script until tor exits (as you said usually as a result of the users typing ctrl-c).

So you can see that traping interupts after tor exists is closing the barn door after the horse has bolted.

I moved the trap to before tor starts and also added a clean shutdown after tor, this is for instances where tor exist with a ctrl-c interupt (e.g. tor fails to start due to error, crashes, or some user input causes tor to exit without the need for ctrl-c).

Thank you very much, i really do appreciate your answer.
Gave me quite an insight about sh signals for now:O
Ty again

---------- Post updated at 07:00 AM ---------- Previous update was at 03:24 AM ----------

One more thing, from what you said, wouldnt it be better if i had an if clause to check whether tor started successfully and then instruct the /usr/local/etc/rc.d/polipo stop? How is that implemented to the above script? Im kinda messed up with this check, what i tried is:

Code:

if [ $? -eq 1]; then
/usr/local/etc/rc.d/polipo stop;
fi

but it does not work
My shell is tcsh and i got freebsd-8.2-Release

The code you posted is more bash/ksh style, you use tcsh which is a C shell (csh) compatible script (see csh programming considered harmful). If you must stick with tcsh then you need csh style constructs:

Code:

if ( $? != 0 ) then
    /usr/local/etc/rc.d/polipo stop
endif

But this test may be unnecessary as you appear to want polipo stopped after tor has exited, regardless of any errors.