Search for a range of lines

# Use awk's range operator, a comma, to print an entire # function definition in an init script awk '/action\(\) {/ , /}/' /etc/init.d/functions

    action() {
      local STRING rc

      STRING=$1
      echo -n "$STRING "
      shift
      "$@" && success $"$STRING" || failure $"$STRING"
      rc=$?
      echo
      return $rc
    }

Get the directory of the currently running script

# $0 gives the relative path the script was invoked with, so: # ./script.sh gives ./script.sh # ~/script.sh gives /home/user/script.sh # # $(pwd) prints the working directory, not the script file location # # `which $0` is a special use to get the full path and name of the script # Called this way, which does not do its normal search of $PATH # # Enclose in double quotes to account for folders with spaces in them RUNDIR=$(dirname "$(which "$0")")

Override noclobber

set -o noclobber echo "test" > test.txt echo "test" > test.txt # bash: test.txt: cannot overwrite existing file echo "test" >| test.txt

Variable length expansion

# How many characters are in variable XYZ? XYZ="12345" echo ${#XYZ} # How many parameters did you feed me? function howmany () { echo ${#@} } howmany 1 2 3 4 5 6789 # How many elements are in array XYZ? XYZ=( 1 2 3 4 5 6 7) echo ${#XYZ[@]}

Is this an integer?

function isInteger () { echo "$@" | grep -q -v "[^-0-9]" } if isInteger 1975; then echo "Yes, that is an integer"; fi

Yes, that is an integer

Instant HTTP Server

Starts a web server on port 8000 and serves up the current directory:

python -m SimpleHTTPServer

Scary? Damn straight.

Get the network ID from an IP address and subnet mask

echo "192.168.5.133 255.255.255.250" | \ awk 'BEGIN {FS="[. ]"; OFS="."} {print and($1,$5), and($2,$6), and($3,$5), and($4,$8)}'

192.168.5.128