# 2014 Jan 17
# Lecture 6
# Annotated history

# Show the symbolic link of the dictionary file on klaatu (your Linux distro may have it in a different location)
    1  ls -l /usr/share/dict

# Show the contents of the file pointed to by the symbolic link (linux.words)
    2  more /usr/share/dict/words

# Perform the word count (wc) command on the file to show that it contains quite a number of entries
    3  wc /usr/share/dict/words

# Show the contents of the current working directory to show that words is not there
    4  ls -l

# Use the ln command to create a link (pointer) to the dictionary file to use as a convenient shortcut
    5  ln -s /usr/share/dict/words words

# Show the contents of the current working directory again to show the new entry, words 
# (may show in a different color to indicate that it is a link)
    6  ls -l

# Perform the word count (wc) command on the (linked) file, words
    7  wc words

# Use grep to find an exact match to this text (can have anything else in front of or behind it)
    8  grep loofah words

# Use grep to find an exact match to this text (can have anything else in front of or behind it)
    9  grep twig words

# Use grep to find an exact match to this text (can have anything else in front of or behind it)
   10  grep 'twig' words

# Now use the special characters ^ and $ to anchor the pattern to the front and end of the line
   11  grep '^twig$' words

# Now use the special character ^ to anchor the pattern to the front of the line
   12  grep '^twig' words

# Now use the special character $ to anchor the pattern to the end of the line
   13  grep 'twig$' words

# Find words that start with the letters q and u (can be lower or uppercase)
   14  grep '^[Qq][Uu]' words

# How many of those words are there?
   15  grep '^[Qq][Uu]' words | wc

# Find words that start with the letter q (can be lower or uppercase), but NOT followed by a u or U
# Pay attention to whether ^ is inside or outside of [ ]
   16  grep '^[Qq][^Uu]' words

# There are a lot fewer of q without u words (useful to know in Scrabble)
   17  grep '^[Qq][^Uu]' words | wc

# Find words that start with lowercase q, have at least one letter following q, and ending in ing, with anything in-between
   18  grep '^q.*ing$' words

# Use escaped parentheses \( \) to surround a pattern
# Anchor pattern at the beginning and end of the line (^ and $ special characters)
# Match the first part of the pattern again \1, so things like aa, dodo, hiphip, and so on are matched
   19  grep '^\([a-z]*\)\1$' words