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

8
exercises/scripts/elevator/solution.py Normal file
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@ -0,0 +1,8 @@
#!/usr/bin/env python
# coding=utf-8
class Elevator(object):
def __init__(self, direction=0, position=0):
self.direction = directopn
self.position = position