Linux Shell Tutorial Homework

Homework exercises from Linux shell tutorial.

Shell scripting is like magic tricks for programmers...

NOTE: All the scripts must be compatible with Bash v4.3.

1. Counting files by type (10 points)

Write two versions of script that counts how many files there are of each type in a given directory. Use file filename. Script should accept a directory name. Output should look like:

$ ./script path/to/directory/name
5 gzip compressed data
20 directory
3 Bourne-Again shell script
11 ASCII text
3 empty
1 UTF-8 Unicode text
1 FORTRAN program

One version may use whatever Linux tools you find on Triton, but the other one can use only BASH built-in functionality. The only exception is file utility itself.

2. Aalto account checker utilty (10 points)

Expand /scratch/scip/BASH/bin/expires script to get a proper utility out of it. Your new script should:

accept list of users either as input parameters ./expires user1 user2 user3 user4
or as STDIN w -h | cut -c1-8 | sort -u | ./expires
if run with no arguments or STDIN report for current $USER
report account expiration date
report amount of days till account is expired

report date when password has been last changed. Example:

$ ./expires user1 user2
user1
  Account expires: Sun Jan  8 23:00:00 EET 2019
  Days till expiration: 234
  Password last changed: Wed Dec 14 16:45:12 EET 2017
user2
  ...

accept -c option, and if given, make a compact version. Example:

$ ./expires -c user1 user2
user1:2019-01-08:234:2017-12-14
user2:...:....:

Note: script will work on Aalto Linux servers and workstations, not on Triton.

3. Bubble sort and Shell sort (10 points)

Implement Bubble and David Shell sort algorithms using BASH internal functionality only. Make a performance comparison for sorting 1000 random numbers with time utility.

(Shellsort)

For generating random numbers one can use function we have developed during the tutorial. Alternatively, script can accept random numbers as standard input, generated like shuf -i1-1000 -n1000 or in a similar way.

Optionally, if only Bubble sort algorithm is implemented, it is 4 points.

4. Text analyzer (10 points)

Write a script that accepts a file with random text either from STDIN or a filename as a script argument (-f filename). Your script must accept several options and take an action based on them

-c      reports total number of characters in the document
-w      reports total number of words in the document
-t n    top 'n' most common words, where n is any positive integer
-s      sorted list of how often appear words of different lengths, like
          words #    word length
               56    1
               34    2
               87    3
               23    4

As a text file example, script should be able to analyze bash.txt

Usage cat bash.txt | ./script -t 10 -w or ./script -f bash.txt -s

When counting words, word may consist of letters only i.e. [a-zA-Z]+. Pay attention to 'instance.' 'integer;' occurrances and alike. Punctuation, special characters, digits, must be cleaned up before counting word lengths. The rest items like paths, variable names, URLs etc can be omitted for this assignment.

5. Sanajahti solver (10 points)

Originally it is a game, known in English as Wordz. The game play is connecting letters to words on 4x4 matrix of letters. In any direction, any connection be it edge or corner (diagonal) works.

Pick up dictionary from words_alpha.txt (remember tr -d '\15\32' < windows.txt > unix.txt)

The script should accept a 16 characters line like DOBEWCMEEETPCNXT, that corresponds to 4x4 matrix

DOBE
WCME
EETP
CNXT

The script must output found words one by one to STDOUT. The script must accept a dictionary file as an argument.

Example: ./sj_solver -d words.txt DOBEWCMEEETPCNXT

jaantollander / Linux-Shell-Tutorial