bin/gxpr

   1 #!/bin/sh
   2 # Usage: gxpr <expression>
   3 # Like expr(1), but uses Google's calculator to evaluate <expression>.
   4 #
   5 # Math examples:
   6 #   $ gxpr '1 + 1'
   7 #   2
   8 #
   9 #   $ gxpr 2 ^  16
  10 #   65536
  11 #
  12 #   $ gxpr '(2 ^ 1) + (2 ^ 2) + (2 ^ 3) + (2 ^ 5)'
  13 #   46
  14 #
  15 #   $ gxpr '5*9+(sqrt 10)^3='
  16 #   76.6227766
  17 #
  18 # Conversion examples:
  19 #   $ gxpr 1GB in KB
  20 #   1048576 kilobytes
  21 #
  22 #   $ gxpr 10 megabits in megabytes
  23 #   1.25 megabytes
  24 #
  25 #   $ gxpr 2 miles in inches
  26 #   126720 inches
  27
  28 CURL='curl -s --header User-Agent:gxpr/1.0'
  29 SEARCH="http://www.google.com/search"
  30 EXPR=$(echo "$@" | sed -e 's/+/%2B/g' -e 's/ /+/g')
  31
  32 res=$(
  33     $CURL "$SEARCH?q=$EXPR" |
  34     grep '<h2 class=r'      |
  35     perl -pe 's@.*<h2 class=r.*?<b>.*?= (.*?)</b>.*@\1@' |
  36     perl -pe 's@\x{a0}@@g' |
  37     perl -pe 's@ </font>@@g' |
  38     perl -pe 's@<.*?>@@g'
  39 )
  40
  41 # if we don't have a result, assume it's an invalid expression
  42 test -z "$res" && {
  43     echo "invalid expression:" "$@" 1>&2
  44     exit 1
  45 }
  46
  47 echo "$res"