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Week 13 Notes for CST8129
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-Ian! D. Allen - idallen@idallen.ca

*** Keep up on your readings (Course Outline: average 5 hours/week homework)

Remember - knowing how to find out an answer is more important than
    memorizing the answer.  Learn to fish!  RTFM!  (Read The Fine Manual)

Announcement: Final Exam Dec 12 3 hours 11h30 - 14h30 

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Review:
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Exercise #11 - Lunar Lander Game
    Try the demo:   ~alleni/bin/lunarlander
    Read the demo files under Notes: parabola.sh.txt g*.sh.txt

Chapter 8 - Bourne Shell Programming
    8.8 - trapping signals
    See Notes file: interrupts.sh.txt, input_trap.sh.txt

Chapter 3 - Regular Expressions and Pattern Matching
    See 4.7 p.100 (with modifications):
    Ordinary regexp metacharacters: ^ $ . * []
    Extended regexp metacharacters: ? + | () {}
    A backslash reverses the meaning of a regexp character.
    (If it was on, it turns it off; if it was off, it usually turns it on.)

Chapter 4 - The grep Family: grep, egrep, fgrep 
    egrep uses Extended regexp by default.
    fgrep doesn't use regexp at all.

Chapter 5 - sed, the Streamlined(sic) Editor
    Basic regexp substitutions:
    sed -e 's/regexp/text/g' -e 's/regexp/text/g' [ files... ]

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This week:
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More on sed:

    Using & in LHS of s///   (see Example 5.16 p. 138)

More extended regexp metacharacters (see "New with egrep" table p. 96):

    + - (extended) one or more ->  x+  ->  xx*
    ? - (extended) zero or one ->  xy?z  ->  x(y|)z  ->  (xz|xyz)

Chapter 4 - The grep Family: grep, egrep, fgrep 

  grep family options:  -v, -A, -B and -n, -l, -i, -c, -w

  Exercises: ALL
  Text errata: Q10 p.124   s/insensitive/sensitive/

Chapter 5 - sed, the Streamlined(sic) Editor

  sed options to know:  -e, -n, -f

  addressing:  /regexp/   1   $
  combo:  /regexp/,23    23,/regexp/    23,$
  negation address range suffix: !
  sed commands:   a  c  d  i  p  q  s
  WARNING: y command doesn't take ranges like tr does!

  s/// substitution flags:  g  p

  Exercises: ALL

Chapter 6 - The awk Utility
 
  On Linux awk and gawk are the same program, essentially equivalent
  to "nawk".

  Note: awk uses floating-point arithmetic, not integer!
   - be careful of testing equality with floating point!
   -  echo hi | awk ' ((1/3)+1-1)*3 == 1 { print } '   <== NO OUTPUT!

  Read: 6.1.1 (p. 157) through 6.12.8 (p.202)
   - OMIT 6.4.2  (0FMT)
   - OMIT 6.4.3  (printf)
   - 6.6.3,6.10.4 not all versions of awk support a multiple character FS
     - avoid using multi-char FS or -F if you can
   - OMIT 6.11.2,6.12.7  ( ? : query conditional operator)

  built-in variables: NF NR
  field selection expressions: $1 $2 $NF $(NF-1) $(1+3)

  awk options: -F

      $ awk -Fx ' Boolean_Expression { action } ' [... files ...]

  simple Boolean Expressions:

  $1 == "hi"   $1 < 5   /foobar/   $1 ~ /^[fF]oobar/

  compound expressions can use arithmetic, ||, and && like C Language:

  ( $1+$2 ) >= 500  &&  $3 ~ /^Moneybags/  { print }

  WARNING: awk silently treats non-numeric strings as zero in arithmetic!

  $ echo one two three | awk '{ print $1+$2+$3 }'
  0                   <=== no error message!

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Next week:
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  Read: 6.13.1 (p. 203) through 6.26.7 (p.278)
   - OMIT 6.14 redirection and pipes
   - OMIT 6.15 pipes
   - OMIT 6.16.6 printf
   - OMIT 6.16.7 redirection and pipes
   - OMIT 6.16.8 pipes
   - OMIT 6.23 user-defined functions
   - OMIT 6.23,6.26.6 user-defined functions
   - OMIT 6.25.1 fixed fields (but read use of gsub)
   - OMIT 6.25.2 multi-line records
   - OMIT 6.25.3 form letters
   - OMIT 6.26.2 time functions
   - OMIT 6.26.4 getline