useful shell one liners

The following are a few one liner shell commands I occasionally use:

  • Get the current external ip address:
    GET | tr -d ‘ /:-z’
  • Get an estimation of postfix mail queue:
    mailq|wc -l
  • Find out if a process is running from name:
    ps uxa|grep -i processname
  • Get a list of directories sorted by size:
    du -s -h *|sort -h
  • ping a list of ips:
    cat file-of-ips | xargs -n 1 -I ^ -P 50 ping ^
  • ping a list of hosts in a file:
    cat hosts|xargs -n1 ping -c 1

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