Ghostscript is a suite of software based on an interpreter for Adobe Systems’ PostScript and Portable Document Format (PDF) page description languages.
It can be used to merge PDF files or extract specific pages from a PDF file from the command line in Linux (Ubuntu) without loosing the quality. (more…)
When a file or a directory is created in a Linux file system, a name and a uniq inode number is assigned to it.
An inode is a data structure that contains information about a disk block location of a file or a directory and may include metadata (times of last change, access, modification), as well as information about the owner and permissions.
The number of inodes is defined during the file system creation and can’t be increased without reformatting the partition.
In this note i will show how to check the inode usage in Linux, how to list top directories sorted by inode usage and how to show the inode number of a file or a directory. (more…)
An ARP (Address Resolution Protocol) is a communication protocol that works on a “Physical (Data-Link)” layer of a TCP/IP stack and is used to discover a MAC address of a device on a LAN (local-area network) based on its IP address.
An ARP table is used to store the discovered pairs of the MAC and IP addresses.
In this note i will show how to display the ARP table and how to clear the ARP cache using the Windows arp command. (more…)
Each IP packet contains information about its origin and destination.
A routing table contains the information necessary to forward an IP packet along the best path toward its destination.
In this note i will show how to display the routing table in Windows using the route print command. (more…)
A randomSeed(analogRead(0)) in Arduino initializes the pseudo-random number generator that reads the random analog noise from an unconnected analog pin 0 and floats to relatively random values between 0 and 1023.
This shuffles the random() number generator each time you start the Arduino sketch.
In this note i will show the examples of how to generate random numbers and create random delays in Arduino using the randomSeed() and random() functions. (more…)
Minikube is a single-node Kubernetes cluster that can be installed on macOS, Linux and Windows.
By default, it starts with 2 CPUs and 2GB of memory, that may not be enough for experiments with some heavy projects.
This note describes 3 easy ways to start the Minikube with more memory and CPUs. (more…)
A USB Keyboard function in Arduino can be used to send keystrokes to an attached computer.
Unfortunately this capability is limited to Arduino boards with the ATmega32u4 microchip i.e. Arduino Leonardo, Arduino Micro and Arduino-compatible Pro Micro (though the last one is really cheap).
Below you will find some code snippets with the examples of how to simulate keystrokes, including a multiple key pressing, using the Arduino boards.
To make it more simple, the keystrokes in the examples below will be called in a loop, so there is no need to install any additional hardware buttons. (more…)
Let’s say you have connected to your computer some human interface device (HID) that can simulate key presses (e.g. Arduino with a button) and you want to do some debug.
If you wonder how to capture a keystroke in Windows and detect which key has been pressed, this can be easily done from the PowerShell. (more…)
The .htaccess file is a configuration file for the Apache web server, that can be used to redirect requests from specific IP addresses to another resources.
In this short note i will show how to redirect requests from one or several IP addresses via .htaccess file to a specific web page or another website. (more…)
The .htaccess file is a configuration file for the Apache web server, that can be used to restrict access to a web-site from a specific IP or a range of IP addresses.
In this note i will show how to deny access from one or several IP addresses via .htaccess file and how to block access from a range of IP addresses or from entire subnets. (more…)