Initial commit for Michal CTO exercises

Initial commit for exercises assigned to me by Michal.

Among others:
  * cat - unix command implementation in ruby
  * grep - unix command implementation in ruby
  * ls - unix command implementation in ruby
  * ps - unix command implementation in ruby
  * pwd - unix command implementation in ruby
  * wc - unix command implementation in ruby
  * ONP converter (reverse polish notation)
  * Roman numerals to decimals converter

Author: polishExperiment

.gitignore

@@ -0,0 +1 @@
+.idea

michal_zadania/cat/bin/cat.rb

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+#!/usr/bin/env ruby
+
+unless filename = ARGV.first
+  puts "You need to pass name of the file"
+  exit 0
+end
+
+
+File::open filename do |file|
+  print file.read
+end
+

michal_zadania/grep/bin/grep.rb

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+#!/usr/bin/env ruby
+
+needle, filename = ARGV
+
+unless needle && filename
+  puts 'You need to pass needle and filename argument'
+  exit 0
+end
+
+def colorize text, color_code
+  "\e[#{color_code}m#{text}\e[0m"
+end
+
+File::open filename do |file|
+  while line = file.gets
+    print colorize line, 31 if line.include? needle
+  end
+end
+

michal_zadania/grep/kaka

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+kaka kakak

michal_zadania/ls/bin/ls.rb

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+#!/usr/bin/env ruby
+
+# This works for bare 'ls' and partially for 'ls -l'
+
+
+# please ignore this from here --------------------
+
+#puts sprintf("%o",File.world_readable?('kaka'))
+# puts "\n\n\n\n"
+#
+=begin
+s =  File.stat('kaka')
+puts s.inspect
+puts "\n\n\n\n"
+s.mode
+puts sprintf("%o", s.mode)
+puts s.uid
+puts s.gid
+=end
+# till here ( I will probably need some of that)------
+
+arguments = ARGV
+
+if arguments.length > 1
+  puts 'You can\'t pass more than one argument'
+  exit 0
+end
+
+argument = arguments.first
+
+if argument.nil?
+  Dir.glob('*').sort.each {|file| print "#{file}  "}
+
+  print "\n"
+  exit 0
+end
+
+
+# identify passed options if there is an argument at all
+if argument =~ /-[a-zA-Z0-9]+/
+  argument_chars = argument.chars
+
+  # remove '-' from arguments' characters
+  argument_chars.shift
+
+  if argument_chars.count('l') > 0
+    Dir::glob('*').sort.each do |file|
+      if File::file? file
+        print '-'
+      else
+        print 'd'
+      end
+
+      permissions = File::world_readable? file
+
+      if permissions.nil?
+        print '-' * 9
+      else
+        permissions = sprintf "%o", permissions
+        permissions = permissions.to_s.chars
+        permissions[0]
+      end
+
+      puts "rw-rw-r-- 1 visuality visuality 777 maj 11 15:44 #{file}"
+    end
+  end
+
+else
+  puts 'You need to pass argument in the form of hyphen followed by parameters as in "-la"'
+  exit 0
+end

michal_zadania/onp/bin/onp.rb

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+#!/usr/bin/env ruby
+
+# todo write it as a class/classes
+
+OPERATOR_REGEX = /[+\-*\/^]/
+NUMBER_REGEX = /[0-9]/
+OPERATOR_PRIORITIES = { '^' => 4,
+                        '*' => 3, '/' => 3,
+                        '+' => 2, '-' => 2,
+                        '=' => 1,
+                        '(' => 0, ')' => 0 }
+
+def extract_number index, symbols
+  number_string = ''
+
+  while symbols[index] =~ /[0-9]/
+    number_string += symbols[index]
+    index += 1
+  end
+
+  return number_string
+end
+
+def convert_to_onp chars
+  output = []
+  stack = []
+  error = nil
+
+  index = 0
+
+  breakpoint = chars.length
+
+  loop do
+    case
+      when chars[index] == '('
+        stack.push chars[index]
+        index += 1
+      when chars[index] == ')'
+        until stack.last == '('
+          output.push stack.pop
+        end
+        stack.pop
+        index += 1
+      when chars[index] =~ NUMBER_REGEX
+        number = extract_number index, chars
+        index += number.length
+        output.push number
+      when chars[index] =~ OPERATOR_REGEX
+        while stack.last && OPERATOR_PRIORITIES[stack.last] >= OPERATOR_PRIORITIES[chars[index]]
+          output.push stack.pop
+        end
+        stack.push chars[index]
+        index += 1
+      when chars[index] =~ /\s/
+        index += 1
+      else
+        error = "Program encountered unrecognized character: '#{chars[index]}'"
+        break
+    end
+    break if index >= breakpoint
+  end
+
+  until stack.empty?
+    output.push stack.pop
+  end
+
+  return error ? error : output
+end
+
+filename = ARGV.first
+
+unless filename
+  puts "You need to pass filename argument to the script"
+  exit 0
+end
+
+File::open filename do |file|
+
+  file.readlines.each do |line|
+    line = line.chomp
+
+    onp = convert_to_onp line.chars
+
+    if !onp.is_a? String
+      print line, " becomes "
+      onp.each {|element| print element + ' '}
+      print "\n"
+    else
+      puts onp
+    end
+  end
+end
+

michal_zadania/onp/test.txt

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+1+33*(4+2*3)
+3 / (52 + y * x)
+335*(9-2*44+167)-22
+6+3*82*(7-4)
+(2+6)*(9-8+445)-3
+((2+5)-(3-12))*3+4

michal_zadania/ps/bin/ps.rb

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+#!/usr/bin/env ruby
+
+# Bare 'ps' is much harder than 'ps -aux'.
+# Yet - I started with bare ps and plan on soon delivering it
+# along with 'ps -aux'
+
+Dir.chdir '/proc'
+
+all_processes = Dir.glob('*').select {|file| file =~ /[0-9]+/ }
+
+all_processes.each do |process_id|
+  file = open("/proc/#{process_id}/status")
+end
+
+all_processes = all_processes.map {|process_id| process_id.to_i}
+puts "PID"
+puts all_processes.sort
+
+puts Process.pid
+puts "\n\n\n"
+
+puts ENV['USER']
+puts Process.euid

michal_zadania/pwd/bin/pwd.rb

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+#!/usr/bin/env ruby
+
+puts Dir::pwd

michal_zadania/roman_to_dec/bin/roman_to_dec.rb

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+#!/usr/bin/env ruby
+
+ROMAN_TO_DEC = { 'I' => 1,
+                'IV' => 4,
+                'V' => 5,
+                'IX' => 9,
+                'X' => 10,
+                'XL' => 40,
+                'L' => 50,
+                'XC' => 90,
+                'C' => 100,
+                'CD' => 400,
+                'D' => 500,
+                'CM' => 900,
+                'M' => 1000 }
+
+DOUBLE_ROMAN = ['IV', 'IX', 'XL', 'XC', 'CD', 'CM']
+
+def validate_roman? line
+  line.chars.each do |char|
+    return false unless ROMAN_TO_DEC.key? char
+  end
+
+  return true
+end
+
+def roman_to_dec line
+  sum = 0
+  chars = line.chars
+
+  i = 0
+  i_end = chars.length
+
+  loop do
+    if i+1 < i_end && DOUBLE_ROMAN.include?(chars[i] + chars[i+1])
+      sum += ROMAN_TO_DEC[chars[i] + chars[i+1]]
+      i += 1
+    elsif i+1 <= i_end
+      sum += ROMAN_TO_DEC[chars[i]]
+    else
+    end
+
+    i += 1
+    break if i >= i_end
+  end
+
+  return sum > 0 ? sum : 'empty line'
+end
+
+####################################### body
+
+filename = ARGV.first
+
+File::open filename do |file|
+  while line = file.gets
+    line = line.chomp
+
+    if validate_roman? line
+      puts roman_to_dec line
+    else
+      puts "Not a roman numeral"
+    end
+  end
+end