How to skip command if it is hanging while waiting for response

Shell Programming and Scripting
1

Hello,

I have a script that contains the command "whois 1.2.3.4"

Sometimes this command takes far too long to produce any output and as a result the rest of the script is not executed.

Can anyone suggest a method so that if no output is produced after say 2 seconds the script skips that command and continues on. I imagine some sort of if statement would do this.

Any assistance would be greatly appreciated.

Regards,
Colin

2

Do you have expect installed?
If not, you could run the command in background, save its pid, sleep for 2 seconds and, if the program is still running, kill it.

3

How about tis (if your sleep dosn't support decimal values ie only whole integers you will need to sleep 1 instead and reduce your wait count to 2).
If you don't have the /proc filesystem you will need to run ps -p $WPID 2> /dev/null and test the exit status

#!/bin/bash
whois 1.2.3.4 > /tmp/wi$$.out &
WPID=$!
while [[ -d /proc/$WPID ]] && [[ $((++wait)) -lt 8 ]]
do
    sleep 0.25
done
if [[ -d /proc/$WPID ]]
then
    WHOIS="<unknown>"
    echo "whois taking too long - killing"
    kill $WPID
else
    WHOIS=$(cat /tmp/wi$$.out)
fi
rm /tmp/wi$$.out