Denis Zastanceanu, CC BY-SA 4.0, via Wikimedia Commons
Shell
Getting the current working directory
The environment variable $PWD and the command pwd are essentially synonymous.
pwd has flags for dealing with symlinks.
Absolute (canonical) path
realpath - Turns relative paths into absolute paths
readlink -f - Originally meant to read symlinks. The -f flag means give “cannonical” path.
Elements of a directory
dirname - Strips the rightmost part from a given directory.
basename - Strips all base directories, leaving the last (rightmost) part of a path/file
NOTE: These commands do not check if a file/directory actually exists, they just
manipulate path strings. Also, be careful when dealing with symbolic links and
read the man page to get the desired behavior.
The initial process that runs on a Unix/Linux system is responsible for
forking the rest of the processes that are needed in order to “boot” the
system. This is the core function of an init-system. It is effectively the first process
where execution is handed off from the kernel to “userspace”, where processes
get PIDs, cpu time and network/memory/disk access via calls to the kernel or kernel modules
(drivers).
The find command is a pretty basic utility, but it does have loads of options, which
may be intimidating at first, but keep in mind it has about every criteria you would
possibly need when searching for attributes of files or directories.
It is also the standard way to search files/directories by criteria like name,
date created, size, permissions, user, and more.
The syntax and options may seem irregular compared to other commands,
but I’ll show a few examples:
If you want to schedule a program to run on a Unix based OS, there are
a handful of options, but the prominent ones found on Linux are
cron and systemd timers.
Initially released in 1975, cron has stood the test of time when it comes
to running a task on a schedule and it continues to be the standard solution
for all kinds of users.
How does it work
There is a file called crontab which tells the cron daemon what to run
and when to run it.
For non-commercial purposes documentation or on a website) that reference your connection with Microsoft PowerShell.
Things To Know About PowerShell
First and foremost, PowerShell is unlike traditional Unix/Linux shells such as bash or zsh.
It is explicitly object oriented and the most of the benefits come from the
fact that the majority of “builtin” commands (also known as cmdlets) and
everything related to input/output comes in the form of
objects which in turn have members, methods and inheritance.
This way data is more “structured” compared to shells that deal with plain text.
Browsing the web involves lots of different protocols that most people probably don’t consider.
DNS is one of those protocols, so in this post, we’ll briefly go over the basics of DNS, why browsers
are switching to DNS Over HTTPS (DoH), and how to get public DNS Records.
What is DNS
The core function of DNS (Domain Name System) is to associate Domain Names to IP Addresses and vice versa.
The concept is deceivingly simple, and incredibly useful.
Dear Reader:
This post is aimed at beginners so if you are already familiar with how APIs work,
you might not get much from my explanation, but you are welcome to skim.
One of the most common activities a Web Developer will do is fetch data from some API,
parse it, and then do something with that data, like displaying it on the page.
Reading input line by line is something that seems like a basic and banal
operation, but it’s not really as basic as some higher level languages
make it out.
Let’s look at a couple ways we can do this in Bash and other languages like Python and C.
Bash
The syntax of bash always seems a bit awkward.
For this example, assume we have a file called test.txt and we want
to echo every line.
