wasteland.cc

Shell

Check if script is running with privileges and warn if it isn't. This works with ksh and bash but not sh.. :-(

#!/usr/bin/oksh                            
if [[ usr=$(id -u) -ne '0' ]]; then                                            
    echo -e $USER "sir, you need to run" \"$0\" "as root or with sudo! \n"      
    exit 1                                                                      
else                                                                        
    echo "you are root."
    # run commands here
fi

Books

I have ordered a well used and dog eared copy of Unix Shell Programming (3rd Edition) from Amazon. Looking forward to reading it.

Shell

After some further research I changed shell again, this time to oksh. A portable OpenBSD ksh shell. This is the best port of OpenBSD's default shell and is also kept up to date in the Void Linux packages. It's also portable to a lot of other operating systems making it very useful to pick up and keep.

Shell

Today I learned about the timeout command after adapting my pinglan script to work on OpenBSD. The problem here is that the -w (maxwait) option of OpenBSD's version of ping only supports seconds. This caused the script to take over 8 minutes to ping all possible hosts on my LAN.

So now with timeout inserted into the main loop of the script:

timeout $TIMEOUT ping -c 1 $ip > /dev/null

With $TIMEOUT configured to 0.2 the script now takes just 52 seconds to ping all possible hosts up and return the results.

IRC

> Zoomers have always existed.
> typeset is a shell builtin that is POSIX, but Bash replaced typeset with declare, but then set typeset as an alias. So POSIX scripts will work in Bash, but a Bash script using declare not typeset, will not work in POSIX shell.
> You have to be an absolute c^_^t to do something like this.

Shell

Changed my default shell to match OpenBSD and to avoid bashisms whilst I'm learning to write scripts.

$ chsh void
Changing shell for void.
Password: 
New shell [/bin/bash]: /bin/ksh
Shell changed.
$_

Shell script

A script to find IP addresses of hosts on my network

#!/usr/bin/bash
# Find hosts on LAN
# Edit variables to suit your needs
###################################
NETWORK="192.168.1"               #
SECS="0.2"                        #
###################################

typeset -i i

echo -e "\nPinging addresses 1 to 255\n"
for (( i = 1; i < 255; i++ )); do
    ip=$NETWORK.$i
    ping -c 1 -W $SECS $ip >/dev/null
    if [ $? == '0' ]; then
        echo $ip exists
    fi
done