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README.md
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README.md
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<td align="center"><a href="#programming"><img src="images/programming.png" width="75px;" height="75px;" alt="programming"/><br /><b>Programming</b></a></td>
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<td align="center"><a href="#python"><img src="images/python.png" width="80px;" height="75px;" alt="Python"/><br /><b>Python</b></a></td>
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<td align="center"><a href="#go"><img src="images/Go.png" width="75px;" height="75px;" alt="go"/><br /><b>Go</b></a></td>
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<td align="center"><a href="#shell-scripting"><img src="images/bash.png" width="70px;" height="75px;" alt="Bash"/><br /><b>Shell Scripting</b></a></td>
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<td align="center"><a href="#scripts"><img src="images/bash.png" width="70px;" height="75px;" alt="Bash"/><br /><b>Scripts</b></a></td>
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<td align="center"><a href="#kubernetes"><img src="images/kubernetes.png" width="75px;" height="75px;" alt="kubernetes"/><br /><b>Kubernetes</b></a></td>
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<td align="center"><a href="#prometheus"><img src="images/prometheus.png" width="75px;" height="75px;" alt="Prometheus"/><br /><b>Prometheus</b></a></td>
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<td align="center"><a href="#mongo"><img src="images/mongo.png" width="75px;" height="75px;" alt="Mongo"/><br /><b>Mongo</b></a></td>
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@ -2630,7 +2630,7 @@ Alternatively if you are using a distro with systemd it's recommended to use sys
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history command or .bash_history file
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</b></details>
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##### Linux Permissions
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#### Linux Permissions
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<details>
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<summary>How to change the permissions of a file?</summary><br><b>
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@ -2703,6 +2703,109 @@ True
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* No permissions
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</b></details>
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#### Linux Shell Scripting
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<details>
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<summary>What this line in scripts mean?: <code>#!/bin/bash</code></summary><br><b>
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`#!/bin/bash` is She-bang
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/bin/bash is the most common shell used as default shell for user login of the linux system. The shell’s name is an acronym for Bourne-again shell. Bash can execute the vast majority of scripts and thus is widely used because it has more features, is well developed and better syntax.
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</b></details>
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<details>
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<summary>True or False?: when a certain command/line fails, the script, by default, will exit and will no keep running</summary><br><b>
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Depends on the language and settings used.
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When a script written in Bash fails to run a certain command it will keep running and will execute all other commands mentioned after the command which failed.
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Most of the time we would actually want the opposite to happen. In order to make Bash exist when a specific command fails, use 'set -e' in your script.
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</b></details>
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<details>
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<summary>Explain what would be the result of each command:
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* <code>echo $0</code>
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* <code>echo $?</code>
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* <code>echo $$</code>
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* <code>echo $@</code>
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* <code>echo $#</code></summary><br><b>
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</b></details>
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<details>
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<summary>How do you debug shell scripts?</summary><br><b>
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Answer depends on the language you are using for writing your scripts. If Bash is used for example then:
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* Adding -x to the script I'm running in Bash
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* Old good way of adding echo statements
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If Python, then using pdb is very useful.
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</b></details>
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<details>
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<summary>How do you get input from the user in shell scripts?</summary><br><b>
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Using the keyword <code>read</code> so for example <code>read x</code> will wait for user input and will store it in the variable x.
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</b></details>
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<details>
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<summary>Explain <code>continue</code> and <code>break</code>. When do you use them if at all?</summary><br><b>
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</b></details>
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<details>
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<summary>Running the following bash script, we don't get 2 as a result, why?
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```
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x = 2
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echo $x
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```
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</summary><br><b>
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Should be `x=2`
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</b></details>
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<details>
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<summary>How to store the output of a command in a variable?</summary><br><b>
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</b></details>
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<details>
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<summary>How do you check variable length?</summary><br><b>
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</b></details>
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<details>
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<summary>Explain the following code:
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<code>:(){ :|:& };:</code>
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</summary><br><b>
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</b></details>
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<details>
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<summary>Can you give an example to some Bash best practices?</summary><br><b>
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</b></details>
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<details>
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<summary>What is the ternary operator? How do you use it in bash?</summary><br><b>
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A short way of using if/else. An example:
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[[ $a = 1 ]] && b="yes, equal" || b="nope"
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</b></details>
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<details>
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<summary>What does the following code do and when would you use it?
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<code>diff <(ls /tmp) <(ls /var/tmp)</code>
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</summary><br>
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It is called 'process substitution'. It provides a way to pass the output of a command to another command when using a pipe <code>|</code> is not possible. It can be used when a command does not support <code>STDIN</code> or you need the output of multiple commands.
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https://superuser.com/a/1060002/167769
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</details>
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#### Linux systemd
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<details>
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@ -7285,6 +7388,17 @@ with open('file.txt', 'w') as file:
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<summary>Can you write a function which will print all the file in a given directory? including sub-directories</summary><br><b>
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</b></details>
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<details>
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<summary>Write a dictionary (variable) to a file</summary><br><b>
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```
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import json
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with open('file.json', 'w') as f:
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f.write(json.dumps(dict_var))
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```
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</b></details>
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#### Python OS
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<details>
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@ -8810,17 +8924,7 @@ Bones question: What is the random seek time in SSD and Magnetic Disk?
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Answer: Magnetic is about 10ms and SSD is somewhere between 0.08 and 0.16ms
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</b></details>
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## Shell Scripting
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<details>
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<summary>What this line in scripts mean?: <code>#!/bin/bash</code></summary><br><b>
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`#!/bin/bash` is She-bang
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/bin/bash is the most common shell used as default shell for user login of the linux system. The shell’s name is an acronym for Bourne-again shell. Bash can execute the vast majority of scripts and thus is widely used because it has more features, is well developed and better syntax.
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</b></details>
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## Scripts
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<details>
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<summary>What do you tend to include in every script you write?</summary><br><b>
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@ -8828,59 +8932,24 @@ Answer: Magnetic is about 10ms and SSD is somewhere between 0.08 and 0.16ms
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Few example:
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* Comments on how to run it and/or what it does
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* Adding "set -e" since I want the script to exit if a certain command failed
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* If a shell script, adding "set -e" since I want the script to exit if a certain command failed
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You can have an entirely different answer. It's based only on your experience.
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You can have an entirely different answer. It's based only on your experience and preferences.
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</b></details>
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<details>
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<summary>True or False?: when a certain command/line fails, the script, by default, will exit and will no keep running</summary><br><b>
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Depends on the language and settings used.
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When a script written in Bash fails to run a certain command it will keep running and will execute all other commands mentioned after the command which failed.
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Most of the time we would actually want the opposite to happen. In order to make Bash exist when a specific command fails, use 'set -e' in your script.
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</b></details>
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<details>
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<summary>Today we have tools and technologies like Ansible. Why would someone still use shell scripting?</summary><br><b>
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<summary>Today we have tools and technologies like Ansible. Why would someone still use scripting?</summary><br><b>
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* Speed
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* The module we need doesn't exist
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* We are delivering the scripts to customers who don't have access to the public network and don't necessarily have Ansible installed on their systems.
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</b></details>
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<details>
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<summary>Explain what would be the result of each command:
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* <code>echo $0</code>
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* <code>echo $?</code>
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* <code>echo $$</code>
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* <code>echo $@</code>
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* <code>echo $#</code></summary><br><b>
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</b></details>
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<details>
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<summary>How do you debug shell scripts?</summary><br><b>
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Answer depends on the language you are using for writing your scripts. If Bash is used for example then:
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* Adding -x to the script I'm running in Bash
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* Old good way of adding echo statements
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If Python, then using pdb is very useful.
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</b></details>
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<details>
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<summary>How do you get input from the user in shell scripts?</summary><br><b>
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Using the keyword <code>read</code> so for example <code>read x</code> will wait for user input and will store it in the variable x.
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</b></details>
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<details>
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<summary>Explain conditionals and how do you use them</summary><br><b>
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</b></details>
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#### Shell Scripting - Loops
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#### Scripts - Loops
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<details>
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<summary>What is a loop? What types of loops are you familiar with?</summary><br><b>
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@ -8890,32 +8959,9 @@ Using the keyword <code>read</code> so for example <code>read x</code> will wait
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<summary>Demonstrate how to use loops</summary><br><b>
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</b></details>
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<details>
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<summary>Explain <code>continue</code> and <code>break</code>. When do you use them if at all?</summary><br><b>
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</b></details>
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#### Writing Scripts
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<details>
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<summary>Running the following bash script, we don't get 2 as a result, why?
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```
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x = 2
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echo $x
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```
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</summary><br><b>
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Should be `x=2`
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</b></details>
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<details>
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<summary>How to store the output of a command in a variable?</summary><br><b>
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</b></details>
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<details>
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<summary>How do you check variable length?</summary><br><b>
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</b></details>
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##### Practical
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Note: write them in any language you prefer
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<details>
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<summary>Write a script which will list the differences between two directories</summary><br><b>
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@ -8937,7 +8983,6 @@ then
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mailx -s "Server $SERVERIP is down" -t "$NOTIFYEMAIL" < /dev/null
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fi
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```
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</b></details>
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<details>
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@ -8960,36 +9005,15 @@ done
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</b></details>
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<details>
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<summary>Explain the following code:
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<summary>Write a script that simulates an elevator</summary><br><b>
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<code>:(){ :|:& };:</code>
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Hints:
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</summary><br><b>
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* Think what properties an elevator has (direction, position, ...)
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* Don't forget to use constraints and conditionals (can the elevator move down/up in any case?)
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* It might be more comfortable to implement it with a language that supports OOP
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</b></details>
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<details>
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<summary>Can you give an example to some Bash best practices?</summary><br><b>
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</b></details>
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<details>
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<summary>What is the ternary operator? How do you use it in bash?</summary><br><b>
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A short way of using if/else. An example:
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[[ $a = 1 ]] && b="yes, equal" || b="nope"
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</b></details>
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<details>
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<summary>What does the following code do and when would you use it?
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<code>diff <(ls /tmp) <(ls /var/tmp)</code>
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</summary><br>
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It is called 'process substitution'. It provides a way to pass the output of a command to another command when using a pipe <code>|</code> is not possible. It can be used when a command does not support <code>STDIN</code> or you need the output of multiple commands.
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https://superuser.com/a/1060002/167769
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</details>
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## SQL
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<details>
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8
exercises/scripts/elevator/solution.py
Normal file
8
exercises/scripts/elevator/solution.py
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#!/usr/bin/env python
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# coding=utf-8
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class Elevator(object):
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def __init__(self, direction=0, position=0):
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self.direction = directopn
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self.position = position
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