Install and run your first noSQL MongoDB on Mac OSX

Amazon SQL vs NoSQL

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Install and run your first noSQL MongoDB on Mac OSX

Classified as a NoSQL database, MongoDB is an open source, document-oriented database designed with both scalability and developer agility in mind. Instead of storing your data in tables and rows as you would with a relational database, in MongoDB you store JSON-like documents with dynamic schemas; This makes the integration of data in certain types of application easier and faster.
Why?
MongoDB can help you make a difference to the business. Tens of thousands of organizations, from startups to the largest companies and government agencies, choose MongoDB because it lets them build applications that weren’t possible before. With MongoDB, these organizations move faster than they could with relational databases at one tenth of the cost. With MongoDB, you can do things you could never do before.


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    1. Install Homebrew
      $ /usr/bin/ruby -e “$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)”
      Homebrew installs the stuff you need that Apple didn’t.
      $ brew install wget
    2. Install MongoDB
      $ brew install mongodb
    3. Run MongoDB
      Create the data directory: $ mkdir -p /data/db
      Set permissions for the data directory:$ chown -R you:yourgroup /data/db then chmod -R 775 /data/db
      Run MongoDB (as non root): $ mongod
    4. Begin using MongoDB.(MongoDB will be running as soon as you ran mongod above)Open another terminal and run: mongo

Install and run your first noSQL MongoDB on Mac OSX

References: https://docs.mongodb.com/manual/tutorial/install-mongodb-on-os-x/


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Script with hash tables on windows and Linux

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How to declare and write a script with hash tables on windows and linux

A hash table, also known as a hash map, is a data structure that is used to store key-value pairs. It is an efficient way to store data that can be quickly retrieved using a unique key.


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Here is an example of how to declare and write a script with a hash table in Python:

# Declare an empty hash table
hash_table = {}


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# Add some key-value pairs to the hash table
hash_table[‘key1’] = ‘value1’
hash_table[‘key2’] = ‘value2’
hash_table[‘key3’] = ‘value3’

# Access a value using its key
print(hash_table[‘key2’]) # Output: “value2”

# Modify a value using its key
hash_table[‘key2’] = ‘new value’
print(hash_table[‘key2’]) # Output: “new value”

# Delete a key-value pair using the `del` statement
del hash_table[‘key1’]

# Check if a key is in the hash table using the `in` operator
print(‘key1’ in hash_table) # Output: False

# Output: False

In this example, we declare an empty hash table using the {} syntax. We then add some key-value pairs to the hash table using the [] syntax. We access a value using its key, modify a value using its key, delete a key-value pair using the del statement, and check if a key is in the hash table using the in operator.

I hope this helps! Let me know if you have any questions.

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    • Hash tables with powershell on windows

      Declaration:
      $states=@{“Alberta” = “Calgary”; “British Columbia” = “Vancouver”; “Ontario” = “Toronto” ; “Quebec” = “Montreal”}

      Name
      _____
      Value
      _______
      AlbertaCalgary
      British ColumbiaVancouver
      OntarioToronto
      QuebecMontreal

      Add new key-value in hashtable:
      $states.Add(“Manitoba”,”Winnipeg”)

      Remove key-value in hashtable:
      $states.Remove(“Manitoba”,”Winnipeg”)
      Change value in hashtable:
      $states.Set_Item(“Ontario”,”Ottawa”)
      Retrieve value in hashtable:
      $states.Get_Item(“Alberta”)
      Find key in hashtable:
      $states.ContainsKey(“Alberta”)
      Find Value in hashtable:
      $states.ContainsValue(“Calgary”)
      Count items in hashtable:
      $states.Count
      Sort items by Name in hashtable:
      $states.GetEnumerator() | Sort-Object Name -descending
      Sort items by Value in hashtable:
      $states.GetEnumerator() | Sort-Object Value -descending

    • Hash tables with perl on linux or windows

      Declaration:
      my %hash = (); #Initialize a hash
      my $hash_ref = {}; # Initialize a hash reference. ref will return HASH
      Clear (or empty) a hash
      for (keys %hash)
      {
      delete $hash{$_};
      }
      Clear (or empty) a hash reference
      for (keys %$href)
      {
      delete $href->{$_};
      }
      Add a key/value pair to a hash
      $hash{ ‘key’ } = ‘value’; # hash
      $hash{ $key } = $value; # hash, using variables
      Using Hash Reference
      $href->{ ‘key’ } = ‘value’; # hash ref
      $href->{ $key } = $value; # hash ref, using variables
      Add several key/value pairs to a hash
      %hash = ( ‘key1’, ‘value1’, ‘key2’, ‘value2’, ‘key3’, ‘value3’ );
      %hash = (
      key1 => ‘value1’,
      key2 => ‘value2’,
      key3 => ‘value3’,
      );

      Copy a hash
      my %hash_copy = %hash; # copy a hash
      my $href_copy = $href; # copy a hash ref
      Delete a single key/value pair
      delete $hash{$key};
      delete $hash_ref->{$key};

Hash tables with python on linux or windows

Hash tables are called dictionary in python.
Declaration:
dict = {‘Name’: ‘Zara’, ‘Age’: 7, ‘Class’: ‘First’}
Accessing Values
print “dict[‘Name’]: “, dict[‘Name’]
print “dict[‘Age’]: “, dict[‘Age’]
Output:
dict[‘Name’]: Zara
dict[‘Age’]: 7
Updating Dictionary
dict = {‘Name’: ‘Zara’, ‘Age’: 7, ‘Class’: ‘First’}

dict[‘Age’] = 8; # update existing entry
dict[‘School’] = “DPS School”; # Add new entry
Delete Dictionary Elements
#!/usr/bin/python

dict = {‘Name’: ‘Zara’, ‘Age’: 7, ‘Class’: ‘First’}

del dict[‘Name’]; # remove entry with key ‘Name’
dict.clear(); # remove all entries in dict
del dict ; # delete entire dictionary

Source:

  1. https://technet.microsoft.com/en-us/library/ee692803.aspx
  2. http://www.cs.mcgill.ca/~abatko/computers/programming/perl/howto/hash/
  3. http://www.tutorialspoint.com/python/python_dictionary.htm

reverse a string on Linux and Windows

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How to reverse a string on Linux and Windows

On Linux:


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  1. Using the rev command: The rev command is a utility that reverses the lines of a file or the characters in a string. To reverse a string, you can use the echo command to pass the string to rev:
echo "string" | rev
  1. Using the sed command: The sed command is a powerful utility that can perform various text transformations. To reverse a string, you can use the sed command with the -r option and the 's/.*(.)/\1/g' expression:
echo "string" | sed -r 's/.*(.)/\1/g'
  1. Using the awk command: The awk command is a programming language that is used for text processing. To reverse a string, you can use the awk command with the {print} action:
echo "string" | awk '{print $1}'

On Windows:

  1. Using the powershell command: The powershell command is a shell that provides a command-line interface for Windows. To reverse a string, you can use the powershell command with the -C option and the '[System.Text.Encoding]::Unicode.GetString([System.Text.Encoding]::Unicode.GetBytes("string"))' expression:
powershell -C "[System.Text.Encoding]::Unicode.GetString([System.Text.Encoding]::Unicode.GetBytes("string"))"
  1. Using the cmd command: The cmd command is the command-line interpreter for Windows. To reverse a string, you can use the cmd command with the for loop:
cmd /c "for /L %i in (1,1,%len%) do @echo !string:~%len%-%i,1!"

These are some ways to reverse a string on Linux and Windows. There are other ways to achieve this, using different utilities or programming languages.


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Via shell script on Linux

reverse a string on Linux and Windows

sh-3.2# vi reverse.sh
#### Start Script #####
#!/bin/bash
input_string=”$1″
reverse_string=””

input_string_length=${#input_string}
for (( i=$input_string_length-1; i>=0; i– ))
do
reverse_string=”$reverse_string${input_string:$i:1}”
done

echo “$reverse_string”
##### End Script #####

Let’s run it:

sh-3.2# chmod 775 reverse.sh
sh-3.2# ./reverse.sh Etienne
enneitE

Via powershell script on Windows

#Let’s use the script reverse.ps1 below.
######
$string=”Etienne”
$string_array=$string -split “”
[array]::Reverse($string_array)
$string_array -join ”

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#####Output#####
PS C:\Users\etienne_noumen\Documents\Etienne\Scripting> .\reverse.ps1

E t i e n n e

enneitE

Via powershell script on Windows in one line

([regex]::Matches($String,’.’,’RightToLeft’) | ForEach {$_.value}) -join ”

Via batch script on Windows

::Note: ReverseStr also calls StrLen
::and string length is not greater than 80 chars
:: but can be changed.

@echo off
SetLocal EnableDelayedExpansion
cls
set Str=Etienne
call :StrLen %Str%
echo Length=%Len%
call :ReverseStr %Str%
echo String=%Str%
echo Reverse Str=%Reverse%
exit /b

::—————-
:: Calc Var Length
::—————-
:: %*=Str to Check
:: Returns %Len%
:: —————
:StrLen %*
set Data=%*
for /L %%a in (0,1,80) do (
set Char=!Data:~%%a,1!
if not “!Char!”==”” (
set /a Len=%%a+1
) else (exit /b)
)
exit /b

::—————
:: Reverse String
::—————
:: %* Str to Reverse
:: Returns %Reverse%
::——————
:ReverseStr %*
set Data=%*
call :StrLen %Data%
for /L %%a in (!Len!,-1,0) do (
set Char=!Data:~%%a,1!
set Reverse=!Reverse!!Char!
)
exit /b

Via perl script on Windows or Linux

Via python script on Windows or Linux

def reverse_string(a_string)
return a_string[::-1]
reverse_string(“etienne”) returns “enneite”
Source:

  1. http://www.computing.net/answers/programming/reverse-a-string-in-dos/26004.html

prompt and read input variables from keyboard

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Let’s find how to prompt and read input variables from keyboard while executing a script using shell, perl, python, batch and powershell (windows and Linux)

  • On Linux via shell

    read -p “Enter your name: ” name
    echo “Hi, $name. Let’s be friend!”

  • On Windows via powershell

    $name=read-host “Enter your name:”
    write-host “Hi $name, Let’s be friend!”

  • On Windows via batch

    Set /p Name=”Enter your name:”
    echo “Hi %name%, Let’s be friend!”

  • On Windows or Linux via perl

    print “Enter your name “;
    my $name = ;
    chomp $name; # Get rid of newline character at the end
    print “Hello $name, let’s be friend”;

  • On Windows or Linux via python

    name=input(“Enter your name: “)
    print (“Hello ” + name + ” let’s be friend”)

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