ShellHacks

Arduino Variable Types: Quick Start for Beginners

admin — Sun, 31 Aug 2025 13:13:28 +0000

The concept of an Arduino variable is one of the first things beginners need to understand when programming microcontrollers. Variables store data that your Arduino sketch can use and modify. To declare a variable in Arduino, you must specify its type and name, like int ledPin = 13;. This tells the compiler what kind of data the variable will hold. Choosing the correct Arduino type of variable is important because it affects memory usage and how the data behaves. This guide explains what variables are, how to declare them, and which Arduino variable types are available.

Cool Tip: How to generate random numbers and random delays in Arduino! Read more →

What Is a Variable in Arduino?

A variable is a named space in memory where data is stored. You can change its value during program execution. For example, if you’re reading a sensor, you might store the result in a variable called sensorValue.

How to Declare an Arduino Variable

Use this format:

<type> <variableName> = <value>;

Example:

int temperature = 25;

Here, int is the type, temperature is the name, and 25 is the initial value.

Cool Tip: How to change Vendor ID (VID) and product ID (PID) of the Arduino-based device! Read more →

When to Declare a Variable

Variables should be declared before they are used. You can declare them:

Globally – at the top of the sketch, outside any function. These are accessible throughout the program.
Locally – inside a function like setup() or loop(). These exist only while the function runs.

Why Variable Type Matters

Each Arduino type of variable uses a different amount of memory and behaves differently. Using the wrong type can lead to bugs or wasted memory. It’s important to choose the smallest memory type that fits your data – especially on boards like the Arduino Uno, which has only 2 KB of SRAM.

ℹ️ Efficient memory usage helps avoid crashes and keeps your sketch stable.

Common Arduino Variable Types

Type	Description	Memory Used	Example
int	Integer from -32,768 to 32,767	2 bytes	`int count = 10;`
unsigned int	0 to 65,535	2 bytes	`unsigned int distance = 300;`
long	Integer from -2,147,483,648 to 2,147,483,647	4 bytes	`long time = 100000;`
float	Decimal numbers (approx. 6-7 digits precision)	4 bytes	`float voltage = 3.3;`
char	Single character (ASCII)	1 byte	`char letter = 'A';`
boolean	true or false	1 byte	`boolean isOn = true;`

⚠️ Warning: Avoid using long or float unless necessary—they consume twice the memory of int.

If the variable type is incorrect in an Arduino sketch, the user may encounter several types of errors – some during compilation, others during runtime. Here’s a breakdown of what can go wrong:

Common Errors from Incorrect Variable Types

Compilation error: If the variable is used in a way that doesn’t match its type, the compiler will throw an error like invalid conversion from 'int' to 'char' or cannot convert 'float' to 'boolean'.
Overflow or underflow: Using a type with a limited range (like byte or int) for large values can cause wraparound. For example, int x = 40000; will overflow since int maxes out at 32,767.
Unexpected behavior: If you use a float where an int is expected (e.g., in digitalWrite()), the function may not behave correctly even if the code compiles.
Memory issues: Using large types like long or float unnecessarily can waste SRAM, leading to instability or crashes in larger programs.
Logical errors: If a boolean is used where a numeric value is needed, the logic may fail silently, producing incorrect results.

ℹ️ Always double-check the expected type for each function and match your variable declaration accordingly.

Conclusion

Understanding how to declare an Arduino variable and choose the right Arduino variable types is essential for writing efficient code. Always match the Arduino type of variable to the kind of data you’re working with. This helps your program run smoothly and saves memory.

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PowerShell Select-String in Context: Lines Before & After Match

admin — Wed, 27 Aug 2025 15:09:08 +0000

The grep command in Linux is widely used to search for patterns in files and show surrounding lines using flags like -A, -B, or -C. But when switching to Windows PowerShell, many users struggle to find an equivalent. The PowerShell Select-String command is the answer. To show lines before and/or after a match, use the Select-String command with the -Context parameter. This lets you display a number of lines before, after, or both around the matching line. This guide explains how to use PowerShell Select-String to replicate grep’s context flags.

Cool Tip: Wondering how to grep in Windows? Discover Windows grep command equivalent in CMD and PowerShell! Read more →

Using PowerShell Select-String Context

The Select-String command in PowerShell is the closest match to Linux’s grep. It supports regex, file input, and line filtering. To show lines before and after a match, use the -Context parameter.

ℹ️ The -Context parameter takes two integers: the first for lines before, the second for lines after.

Show N Lines Before Match

To show 3 lines before each match:

PS C:\> Select-String -Pattern "error" -Path "log.txt" -Context 3,0

Show N Lines After Match

To show 2 lines after each match:

Select-String -Pattern "timeout" -Path "log.txt" -Context 0,2

Show Lines Before and After Match

You can adjust the numbers freely:

Select-String -Pattern "disconnect" -Path "log.txt" -Context 5,10

This shows 5 lines before and 10 lines after each match.

Cool Tip: Wondering how to cat in Windows? Discover Windows cat command equivalent in CMD and PowerShell! Read more →

Conclusion

The PowerShell Select-String command is a powerful tool for pattern matching and context display. By using the -Context parameter, you can show lines before match, after match, or both. This allows you to view the match in context.

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Base64 PowerShell Decode & Encode – One-Liners | CheatSheet

admin — Tue, 26 Aug 2025 20:52:07 +0000

On Linux or macOS, encoding and decoding with base64 is simple. But on Windows, there’s no built-in base64 command in CMD or PowerShell. That’s why many users search for fast alternative of the base64 command in Windows. The simplest way to convert Base64 encoded/decoded data is to use PowerShell’s ToBase64String and FromBase64String methods. The one-liners below will let you work with strings and files securely – without sending your data to any third-party tools. This guide shows how to use Base64 PowerShell commands to make all Base64 data converts locally.

Cool Tip: Wondering how to cat in Windows? Discover Windows cat command equivalent in CMD and PowerShell! Read more →

⚠️ Why I shouldn’t use online Base64 tools? Online Base64 tools may log or store your input. If you’re working with secrets, credentials, or private files, use local commands instead.

Encode a string to Base64

PS C:\> [Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes("Yo"))

This encodes the string "Yo" to Base64 .

Decode a Base64-encoded string

PS C:\> [Text.Encoding]::UTF8.GetString([Convert]::FromBase64String("WW8="))

This decodes the Base64 string "WW8=" back to plain text.

Encode a file to Base64

PS C:\> [Convert]::ToBase64String((Get-Content -path "file.txt" -Encoding byte))

To save the result to a file:

PS C:\> [Convert]::ToBase64String((Get-Content -path "file.txt" -Encoding byte)) `
        > file-base64.txt

ℹ️ PowerShell reads file content as bytes using -Encoding byte, which is required for accurate Base64 conversion.

Decode a base64-encoded file

To write the decoded output to a file:

PS C:\> Get-Content "file-base64.txt" `
        | %{[Text.Encoding]::UTF8.GetString([Convert]::FromBase64String($_))} `
        > file.txt

Base64 in Windows vs Linux/macOS

On Linux/macOS, to encode and decode a string, you’d run:

$ echo "Yo" | base64
$ echo "WW8K" | base64 -d

On Windows, you’ll need PowerShell one-liners like the ones above. Unfortunately, there’s no native base64 command in Windows or base64 CMD tool, but PowerShell fills the gap.

ℹ️ These PowerShell one-liners work in both interactive sessions and scripts, that is ideal for automation!

Cool Tip: Wondering how to grep in Windows? Discover Windows grep command equivalent in CMD and PowerShell! Read more →

Conclusion

These Base64 PowerShell one-liners are powerful, but not exactly easy to memorize. If you’re switching from Linux or macOS, the lack of a simple base64 command in Windows can be frustrating. That’s why it’s best to bookmark this page and treat it as your personal cheat sheet. It gives you everything you need to encode Base64 PowerShell strings or decode Base64 PowerShell files – quickly, securely, and without relying on online tools.

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Find File by Name in Linux – 7 Basic Examples

admin — Fri, 22 Aug 2025 12:51:38 +0000

Finding files in Linux can be tricky, especially when you need to search through thousands of files across multiple directories. However, this is achievable, using the Linux find command. It lets you search for files in Linux recursively by full name, partial name, or pattern.

Many users waste time manually browsing folders. With the right Linux find command syntax, you can locate anything fast. This guide shows how to use the Linux find command to search files recursively by exact name, extension, regex, and more. You’ll also learn how to combine find with grep for finding which of the files contain a certain string.

ℹ️ The find command in Linux is recursive by default. It searches through all subdirectories, unless you explicitly tell it not to, using the he -maxdepth option.

1. Find file by exact name

Search for a file named “notes.txt” in the current directory:

$ find . -type f -name "notes.txt"

ℹ️ The dot ( . ) represents the current directory in the Linux filesystems.

2. Find file by partial name

Find any file with “error” in its name under /var/log:

$ find /var/log -type f -name "*error*"

3. Find file by extension

List all configuration files ending with “.conf”:

$ find /etc -type f -name "*.conf"

4. Find file using regex

Find all files with a 4-digit number and “.log” extension, under /tmp:

$ find /tmp -regextype posix-extended -regex ".*[0-9]{4}\.log"

More information about posix-extended regular expression syntax can be found here.

5. Find hidden files

Recursively show all hidden files under /home/user:

$ find /home/user -type f -name ".*"

ℹ️ In Linux, hidden files are those whose names begin with a dot ( . ).

6. Find file and search contents

Search for the word “timeout” find inside all “.conf” files:

$ find /etc -type f -name "*.conf" -exec grep "timeout" {} \;

7. Find file and show size

Display “.mp4” files with their sizes in human-readable format:

$ find /videos -type f -name "*.mp4" -exec ls -lh {} \;

Conclusion

The find command is a reliable way to find files by name in Linux. Whether you’re using search the files by name or with regex, these examples cover the basics. For more advanced searches, combine the Linux find command with grep or other tools to save time and reduce frustration.

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Roborock Test Mode: How to Run a Full Self-Test Diagnostic

admin — Wed, 20 Aug 2025 19:13:44 +0000

If your Roborock vacuum isn’t working properly – whether it’s sensor errors, cleaning issues, or docking failures – running a built-in self-test can help. To enter Roborock BIT mode: remove the robot from the docking station, turn it off, then hold down the ⏻ Power button and quickly press the 🏠 Home button five times in a row. This activates Roborock test mode for diagnostics. This guide explains how to run the test and what each step means.

🤖 Which Roborock Models Support BIT Mode

BIT (Built-In Test) mode is available on many Roborock models with advanced diagnostic capabilities. These typically include:

Roborock S7 Series
Roborock S8 Series
Roborock Q7 Series
Roborock Q8 Series
Roborock X Series
Roborock T Series

Models with voice feedback, multi-sensor arrays, and smart docking stations are more likely to support BIT mode. If unsure, check your model’s manual or contact Roborock support.

🛠️ How to Enter Roborock BIT Mode

Remove the robot from the dock and power it off by holding ⏻ Power button.
Hold the ⏻ Power button and press the 🏠 Home button five (5) times quickly.
Release all buttons. The robot will announce BIT mode and light up all LEDs.
Press ⏻ Power button once, then 🏠 Home button once to begin the test.
Use 🏠 Home button to move forward through tests; ☐ Spot cleaning to go back.

📋 Full List of BIT Mode Tests

All LEDs
Vacuum Motor
Side Brush
Main Brush
Dust Bin Detection
Water Tank Detection
Water Level Detection
Rear Bumper
Right Front Bumper
Left Front Bumper
Laser Bumper
Wall Sensor
Left Wheel Anti-Collision Sensor
Right Wheel Anti-Collision Sensor
Cliff Sensors (Left Front, Right Front, Left, Right, Left Rear, Right Rear)
Left Wheel Overcurrent
Right Wheel Overcurrent
Main Brush Overcurrent
Side Brush Overcurrent
Left Wheel Forward/Backward Sensor
Right Wheel Forward/Backward Sensor
Detection Wiper Plate
VibraRise Module (Drive Up/Down + Peristaltic Pump)
Gyroscope
Wi-Fi
Microphone Test
LIDAR Test
Pairing
Camera Test
Charging Circuit Test
IR Positioning Front
IR Communication Front
IR Positioning Rear
IR Communication Rear

⚠️ Common Issues BIT Mode Can Identify

BIT mode helps detect hardware and sensor faults that may cause cleaning or navigation problems. Common issues include:

Brush motor failures (side or main brush not spinning)
Sensor malfunctions (cliff, wall, bumper sensors)
Water tank detection errors or missing water level signals
Wheel overcurrent or movement issues due to obstructions
LIDAR or camera faults affecting mapping/navigation
Charging circuit problems or docking failures
IR communication failures (positioning errors)
Microphone or Wi-Fi module issues (connectivity problems)

If BIT mode reports a “Fail” or no response, clean the affected part, check for firmware updates, or refer to the official Roborock repair guide.

And if you’re managing other smart devices, like a NAS system, it’s just as important to follow proper shutdown procedures to avoid damage. See our guide on Shutdown Synology NAS Safely: Avoid Critical Errors for best practices.

✅ Conclusion

BIT mode is a built-in tool for smart vacuum diagnostics. It helps identify issues like brush failure, cliff sensor errors, or water tank detection problems. Use it for regular maintenance or when troubleshooting cleaning problems, firmware issues, or dock errors. It’s a simple way to keep your Roborock running smoothly.

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Force `cp` Command to Overwrite Without Confirmation

admin — Wed, 09 Apr 2025 14:49:26 +0000

The cp command in Linux is used to copy files and directories, but by default, it may prompt for a confirmation before overwriting an existing destination. If you’re running the cp command from some script, these prompts can interrupt the execution. To ensure the cp command overwrites files without confirmation, you can bypass aliases or use the yes command. Below, you’ll find practical ways to achieve this.

Why Does `cp` Ask for Confirmation?

On some Linux systems, cp may be aliased to cp -i, meaning it always prompts users before overwriting files. You can check whether this alias exists by running:

$ alias cp
- sample output -
alias cp='cp -i

If you see alias cp='cp -i', this is why the command asks for confirmation.

Solutions to Force `cp` to Overwrite Without Prompt

Call the cp binary directly: Instead of using the aliased version of cp, run:

$ /bin/cp SOURCE DEST

This bypasses the alias and ensures files are copied without confirmation.

Use the yes command: If cp prompts for confirmation, you can also automate the response by piping yes into the command:

$ yes | cp SOURCE DEST

This automatically confirms any overwrite prompt, ensuring smooth execution in automated workflows.

Conclusion

If the Linux cp command is prompting for confirmation, it’s likely due to an alias. You can either bypass it by calling /bin/cp directly or automate confirmation with the yes command. This allows the files to be copied without prompts, avoiding interruption of the automated scripts.

Related Articles:

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MikroTik Script: Create, Run & Schedule – Example

admin — Thu, 20 Mar 2025 22:17:27 +0000

Fore more efficient network management, different tasks in MikroTik can be automated using scripts. For example, you can create a script to check the availability of some host(s), and it run manually, or automatically using the MikroTik scheduler. This guide will show you how to create, run, and schedule a script on MikroTik RouterOS.

Tested on MikroTik RouterOS v7.14.3.

Creating a Script

To create a script in MikroTik, execute:

[admin@MikroTik] > /system/script/add name=ping-check comment="Ping check
[admin@MikroTik] > /system/script/edit ping-check source

Paste and save the following code:

# Variables
:local host "www.shellhacks.com"

# Ping check
:if ([ping $host count=1] = 0 do={
    :log error "$host is DOWN"
} else={
    :log info "$host is UP"
}

This script pings the specified host, i.e. www.shellhacks.com, and logs the results.

Running the Script

Once the script is ready, you can run it manually by executing:

[admin@MikroTik] > /system/script/run ping-check
- sample output -
Columns: SEQ, HOST, SIZE, TTL, TIME
SEQ  HOST           SIZE  TTL  TIME
  0  135.148.34.70    56  251  80ms911us

Check the logs to ensure that the script is functioning as expected:

[admin@MikroTik] > /log/print
- sample output -
...
22:12:53 script,info www.shellhacks.com is UP

Scheduling the Script

To automate the process, add the script to the MikroTik scheduler and configure it to execute the script at the desired interval, e.g. every minute:

[admin@MikroTik] > /system/scheduler/add disabled=no \
                    interval=1m \
                    name="ping-check" \
                    comment="Ping check" \
                    on-event=ping-check \
                    policy=reboot,read,write,policy,test,password,sniff,sensitive,ftp,romon \
                    start-date=jan/01/1970 \
                    start-time=00:00:00

Checking Logs

After setting up the scheduler, check the logs to confirm the script is running correctly:

[admin@MikroTik] > /log/print
- sample output -
...
22:14:00 script,info www.shellhacks.com is UP
22:15:00 script,info www.shellhacks.com is UP
22:16:00 script,info www.shellhacks.com is UP

Additional Resources

Conclusion

MikroTik scripts are a powerful way to automate different network tasks. By following this guide, you’ll have a functioning script that runs automatically and logs results efficiently. Additionally, you can integrate email or Telegram notifications to get alerted if the destination host becomes unreachable. Check out the additional resources above for more insights into MikroTik’s capabilities.

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The Best Windows Dig Equivalent for DNS Queries

admin — Wed, 19 Mar 2025 15:00:44 +0000

The dig command is an essential DNS troubleshooting tool on Linux and macOS. However, attempting to use it in a Windows Command Prompt or PowerShell will return the errors as follows:

‘dig’ is not recognized as an internal or external command, operable program or batch file.
—
dig : The term ‘dig’ is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

The Windows dig equivalent are the Resolve-DnsName command in PowerShell and the nslookup command in Command Prompt.

Below is a quick guide on how to use these commands to check DNS records in Windows.

‘Dig’ vs ‘Resolve-DnsName’ vs ‘Nslookup’

‘A’ records show the IP address linked to a domain name. Use this to find out which server is hosting a website.

Resolve A records

Linux/macOS Shell:

$ dig shellhacks.com A

Windows PowerShell:

PS C:\> Resolve-DnsName -Name shellhacks.com -Type A

Windows Command Prompt:

C:\> nslookup -type=A shellhacks.com

Resolve MX records

‘MX’ records are for emails. They show which mail servers handle emails for a domain. This helps if there are email problems or you need to check the setup.

Linux/macOS Shell:

$ dig shellhacks.com MX

Windows PowerShell:

PS C:\> Resolve-DnsName -Name shellhacks.com -Type MX

Windows Command Prompt:

C:\> nslookup -type=MX shellhacks.com

Resolve all DNS records

If you want to check all the DNS details for a domain, resolving all DNS records is the way to go. This gives you a full picture, including different types like ‘A’, ‘MX’, and ‘AAAA’ records.

Linux/macOS Shell:

$ dig shellhacks.com any

Windows PowerShell:

PS C:\> Resolve-DnsName -Name shellhacks.com -Type any

Windows Command Prompt:

C:\> nslookup -type=any shellhacks.com

Conclusion

For users searching for a Windows dig equivalent, Resolve-DnsName and nslookup are the best alternatives. While Resolve-DnsName offers more comprehensive details, nslookup is simpler and more widely available. For more guidance on Windows alternatives, see our guides on the Windows “cat” command equivalent and Windows “grep” command equivalent.

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How to Get Telegram Bot API Token in 3 Easy Steps

admin — Tue, 18 Mar 2025 22:53:15 +0000

If you’ve created a Telegram bot and now you need to get its API token, the process is simpler than you might think. Using BotFather, Telegram’s official bot management tool, you can quickly retrieve or regenerate the token. This guide will walk you through the necessary steps to locate your Telegram bot API token quickly and securely. Below are the step-by-step instructions.

Step 1: Open BotFather on Telegram

Ensure you are logged into the correct Telegram account that owns the bot.
Search for BotFather in the Telegram app.
Start a chat with BotFather and use the /start command.

Step 2: Select Your Bot

Use the /mybots command within BotFather.
Browse through your bot list and select the one for which you need the API token.

Step 3: Retrieve Your API Token

Click on the “API Token” button in the bot settings provided by BotFather.
Copy the displayed token or regenerate it if necessary.

Tips for Secure Telegram Bot API Token Management

Always store your API token in a safe, encrypted location.
Avoid sharing the token publicly to prevent unauthorized access.
Regularly update your token to maintain security.

Useful Resources

For a guide on how to rename your bot, check out this tutorial.
Learn how to send a message to Telegram using Python by checking out this guide.

Conclusion

Retrieving the Telegram bot’s API token is a straightforward process. With the help of BotFather, you can quickly locate or regenerate the token is required. Following these steps ensures you’re ready to manage your bot confidently while keeping its credentials safe and secure. Remember to keep your token secure.

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Shutdown Synology NAS Safely: Avoid Critical Errors

admin — Thu, 13 Mar 2025 19:52:32 +0000

How to shutdown Synology NAS? The simplest method is to press and hold the power button until you hear a beep. This initiates a safe shutdown, preventing data corruption. For Synology NAS owners, shutting down the device safely is essential to avoid hardware damage and ensure data integrity. Below, you will find detailed methods for safely shutting down your NAS, along with tips and links to additional resources.

1. Using the Power Button

The easiest way to safely shutdown Synology NAS is by pressing the power button located on the device. This action signals the NAS to complete its shutdown sequence, ensuring all running processes are terminated safely.

Locate the power button on the front panel of the NAS.
Press and hold the button until you hear a beep.
Wait for the NAS to completely shut down before disconnecting power.

Using the power button is completely safe as the system manages the shutdown sequence, avoiding abrupt interruptions that could cause data loss or hardware damage.

⚠️ Warning: If the power button is pressed and held for too long, it may trigger a force shutdown. This can interrupt ongoing processes, cause potential data corruption and the filesystem damage. Always release the button after the beep to ensure a proper shutdown sequence.

2. Shutdown via DiskStation Manager (DSM)

The DSM interface offers another reliable way to shutdown Synology NAS.

Log in to the DSM interface using your web browser.
Click on the user icon in the top-right corner.
Select “Shut Down” and confirm the action.

Shutting down via DSM ensures all active services and tasks are terminated properly. It is especially useful when the NAS is being accessed remotely.

3. Utilizing the DS Finder Mobile App

The DS Finder app provides a convenient option to shutdown Synology NAS from your mobile device.

Open the DS Finder app.
Navigate to the power options.
Select “Shut Down” and confirm the action.

This method is ideal for users who prefer managing their NAS remotely or when accessing the physical device is not feasible.

4. Scheduling a Shutdown

To automate the process, a shutdown schedule can be configured within DSM.

Open DSM and navigate to the Control Panel.
Select “Hardware & Power” and then go to the “Power Schedule” tab.
Set the preferred time for the NAS to shut down automatically.

This is an excellent option for users who want to save energy by turning off the NAS during periods of inactivity.

Conclusion

Shutting down your Synology NAS safely is crucial to maintaining both its durability and data integrity. Whether you use the power button, DSM interface, mobile app, or an automated schedule, these methods ensure a proper shutdown process. For more information, explore Synology NAS: First Time Installation & Setup Guide or learn advanced tools like Synology: Virtual Machine Manager – Install & Setup.

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