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Currently unused questions

Debugging bash scripts

i don't really use this one anymore, it's too much like trivia

determine what is wrong with the following script, if anything.

#!/usr/bin/env bash

PACKAGENAME=$1

pkgrm -a /tmp/noask $PACKAGENAME
echo "Removing $PACKAGENAME..."
if [ $? = 0]; then
   echo "Removal Successfull"
fi

Data Munging

Question: Implement the following function in the programming language of your choice.

Function: collate_records(keys,records). Re-organize an array of records by the value of specified keys.

  • <keys> is an array of keys by which to collate the result.
  • <records> is an array of records, each a table (e.g.: Hash in Ruby, Dict in Python) that has a value for each key in <keys>.

The function returns a table of tables, length(keys) deep, in which the keys of each table are the unique values of all the records for that key, and the value of each key is a table of records having that value collated by the remaining keys. For the innermost tables, the value of each key is an array of the records having all of the values specified by enclosing keys.

Example in Ruby notation ([a,b] is an array; {k=>v} is a hash table):

    collate_records(
     [ 'region', 'status', ],
     [
        { 'name' => 'srv-1', 'status' => 'up', 'region' => 'us' },
        { 'name' => 'srv-2', 'status' => 'down', 'region' => 'us' },
        { 'name' => 'srv-3', 'status' => 'up', 'region' => 'eu' },
        { 'name' => 'srv-4', 'status' => 'up', 'region' => 'eu' },
     ]
    )

returns

    {
      'us' => {
        'up' => [
          { 'name' => 'srv-1', 'status' => 'up', 'region' => 'us' },
        ],
      'down' => [
      { 'name' => 'srv-2', 'status' => 'down', 'region' => 'us' },
    ],
    },
      'eu' => {
        'up' => [
          { 'name' => 'srv-3', 'status' => 'up', 'region' => 'eu' },
          { 'name' => 'srv-4', 'status' => 'up', 'region' => 'eu' },
        ],
     },
   }

Text Processing

You have been asked to troubleshoot a system that processes text documents that have been fetched over a network. The most recent batch of files has been corrupted in an unusual way and unfortunately the originals are not longer available.

The corruption consists of exclamation point characters, !, inserted between other characters in the file at random. Characters have not been removed or replaced, only added. For example, the first paragraph of Dostoevsky's, Notes from Underground, now looks like this:

I am a s!ick man. ...  I am a spiteful m!an.  I! am an unatt!ra!ctive man. ! I
believ!e my liver is diseased.  However, !I k!no!w nothing at all a!bout my
disea!se, !and do not! know for cer!tain what ails me.!  I don't cons!ul!t a doctor
for it, and never have, though I have a respect f!o!r medicine and !d!octors.
Besides, I! am extremely superstitious, sufficiently so to respec!t medicine,!
anyway! (I !am well-educat!ed enough! not !to !be superstitious, b!ut I am
supersti!tious).  N!o, I refuse to c!onsul!t a doctor from spite.!  That! y!ou
probably will! not und!erstand.  Wel!l, !I understand! it, though.  Of cour!se, I!
can'!t explain! wh!o it is precisely that I am! mor!tifying in this c!ase by my
spite: I !am perfectly we!ll aware that I c!a!nnot !"pay out" !th!e doctors by no!t!
consultin!g !them; I k!now bett!er than anyone t!hat by all th!is !I am only!
in!j!uring myself and! no! one else.  !But still,! if I don't consult a do!c!t!or it is
f!rom spite.  !My liver! is !bad, well--let! it get worse!

Design a procedure for restoring the text to it’s original form. Sketch out an implementation in either pseudo code or the language of your choice, e.g., python, bash, ruby, lisp, etc.

Ruby idioms

What Ruby programming idiom employs the module method "included"? Give an example from a real-world gem or library, explaining how and when the relevant code is invoked, as well as the effect is on the caller.