Quick bash oneliners

The following are a few one liner shell commands I occasionally use: Get the current external ip address: GET checkip.dyndns.org | tr -d ' /:-z'

Quick Postfix MailQ estimate

Get an estimation of postfix mail queue:

mailq|wc -l

Process Running

Find out if a process is running from name:

ps uxa|grep -i processname

disk usage by size

Get a list of directories sorted by size:

du -s -h *|sort -h

Available hosts by ip

ping a list of ips: cat file-of-ips | xargs -n 1 -I ^ -P 50 ping ^

Available hosts by hostname

ping a list of hosts in a file: cat hosts|xargs -n1 ping -c 1

Start All Xen VMs

If you need to start all Xen Hosts on a machine, try the following simple script:

ARRAY=`xe vm-list tags="autostart" | grep uuid | awk '{ print $5 }'`

for f in $ARRAY
        VM_NAME=`xe vm-param-get uuid=$f param-name=name-label`
        echo "Starting $VM_NAME"
        /opt/xensource/bin/xe vm-start uuid=$f

Scan a subnet

Many tools exist to scan networks such as nmap, *nessus. However, many times you are on a machine where those tools are not available.

Here is a quick script to do just that:

if [ $# -ne 0 ]
  echo "Subnet provided $1"
printf "\nPinging network $subnet.1-$subnet.254\n\n"

for addr in $(seq 1 254)
( ping -c 1 -t 3 $subnet.$addr > /dev/null 2>&1 && echo - Ping reply: $subnet.$addr  ) &
sleep 2
printf "\n"