Linux Tips, Tricks and Tutorials

Shell scripting and chaining together small tools to perform real world tasks is a very powerful concept and Linux / Unix lets us do that.

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Output, Assign, Pipe and Redirect a Heredoc in a Shell Script

You may want to do this when working with multi-line strings.

Setting Up a TCP Listener and Connecting to It with Netcat

This can be handy to test connecting to a specific port.

Git Diff 2 Different Commits, Tags or Branches

Compare what changed between 2 points in time to help identify errors in production or evaluate changelogs.

Create Read-Only AKA Immutable Variables in Bash

Sometimes a little bit of extra clarity can go a long ways such as being explicit when a variable won't change.

Wait for Input in a Graphical Code Editor in a Shell Script

For example, your script might launch VSCode and wait for a file to be edited and then do something once the file is closed.

Hiding User Input in a Shell Script

This could be useful when asking users to input passwords, API tokens or anything you don't want printed to the screen.

Color Your Shell Prompt Red If the Last Command Threw an Error

We'll cover examples that work with both bash and zsh. We'll go with red for errors and your default color for non-errors.

Difference between Double Ampersand and Semicolon in a Shell Script

Sometimes they appear to do the same thing but there is quite a big difference between both solutions.

Automate Suspending Kubernetes Cron Jobs with find and sed

Treat yourself by automating mundane tasks like setting a bunch of YAML properties from true to false and vice versa.

Get the MD5 Hash of a File with OpenSSL

This is a fairly compatible way that works on most distros of Linux and macOS without needing extra dependencies.

Git Cherry Pick Examples to Apply Hot Fixes and Security Patches

Cherry picking lets you apply 1 or more commits from one branch to another, it shouldn't be abused but it does have its place.

Count All Git Commits in a Repo

This could be useful to compare activity across multiple repos.

Customize FZF's CTRL + T Binding with FZF_CTRL_T_OPTS to Preview Files

This lets us quickly preview files in less or whatever tool you prefer.

Validate File Types by Reading the First Few Bytes of a File

Easily confirm if a file is really a jpg, png, gz or whatever file you want. We'll use the od command line tool or Python and Ruby.

Get Video Duration in Seconds Using FFmpeg / FFprobe

We'll get the value back in seconds as well as HH:MM:SS if you prefer.

Delete Lines That Match a Pattern or the Opposite Pattern Using sed

This could be useful to remove unwanted lines in a file or output, such as processing a file and writing out a new file to analyze.

Expand Tilde to Home Directory When Reading User Input in Bash

A common use case is to ask a user to define a path using a tilde but you want that to really be their home directory path.

Modifying Shell Arguments with the set Command

This could be handy to dynamically adjust the arguments of a program based on whatever custom condition or criteria you need.

Ignore Sudo in a Shell Script If You're Running as Root

This can be used to run a command as root outside and inside of Docker where sudo might not be available.

Reduce Docker Images by 20 MB by Verifying APT Packages without gnupg

When working with package sources you can pass the plain text asc key into signed-by instead of a binary gpg key.

Delete Empty Directories on the Command Line with Find

Quickly recursively delete all empty directories. We'll be able to perform a dry run too.

Monitor the Output of a Program for Changes Using the Watch Command

This sure beats running a command and hitting the up arrow dozens of times per minute while you wait for a change.

Wrap Text to X Characters on the Command Line with fold or fmt

They're core GNU tools that you likely already have available. It's handy to make output more readable on high resolution displays.

Deleting Specific Lines in a File with sed or yq

We'll go over deleting 1 or more lines that match a regex as well as deleting specific lines by number reference.

Pretty Print JSON in Your Terminal with jq or Python

We'll go over creating a script to read in JSON from a file or your clipboard complete with multi-line syntax highlighting.

Detect If a Shell Script Is Being Executed or Sourced

We'll go over how to determine this and cover a use case of when you might want to create a script that handles both.

Using trap to Run a Command after Your Shell Script Exits

This can be handy to delete temp files that your script creates or to always write a log file out if the script works or fails.

Clearing and Restoring Your Current and Saved Shell History with Zsh

You may want to do this before recording videos, giving presentations at work, demoing something for clients or live streaming.

How Would You Improve This Shell Script?

The script handles calling another script with an optional position argument and 0 or more command line flags.

Check When a Server Was Shutdown or Reboot with uptime, who and last

This can help detect how long a server has been up or when you may have powered it off. We'll track reboots too.

Create Parent Directories with Curl Using the --create-dirs Flag

This can save you from writing a file to a temporary directory and then moving it after using mkdir.

A Few Examples of Using Brace Expansion with Bash

We'll go over examples with echo, how to use it for creating files and making multiple curl requests. It's a flexible feature!

Recursively Print Files with Their Path Using Find, Cat or Tail

Here's a few ways to output multiples files so you can skim which file has which content.

Moving a Bunch of Shell Alias Functions into Their Own Script Files

Aliases and shell functions serve a similar purpose, but they don't need to be kept in the same file.

Git Restore All Unstaged and Untracked Files Back to their Latest Commit

Sometimes you want to experiment and revert the changes you've made to their last known good state or dispose of files.

Parse Command Line Positional Arguments and Flags with Bash

We'll go over using short flags, long flags, flags with and without values and required positional arguments.

Splitting Strings by a Delimiter with IFS or Bash's String Replace

There's a couple of ways to split strings into an array with a 1 character or multi-character delimiter.

Create Video Clips with FFmpeg in Seconds

Provide a file along with a start / end time and ffmpeg will do the rest. We'll also make a tiny wrapper script to make it easier to use.

Using a Custom SSH Key to Access a Private Git Repo

This is useful if you have a handful of repos using a different SSH key than your usual default key.

Using curl with Multiline JSON Data

Occasionally I want to POST human formatted JSON with curl, here's how to do that without using shell hacks or temp files.

Associative Arrays in Bash (AKA Key-Value Dictionaries)

Starting with Bash 4+ you can assign arrays with keys and values. Here's how to declare, update and loop over them.

An Alias to Create Shell Scripts

Most shell scripts I create start the same, this saves a bit of time from having to create, chmod the file and set a few options.

A Few Examples of Using the Tee Command

Tee lets you read from stdin and write to both stdout and a file at the same time. It optionally supports appending to a file.

Switching from an RSA SSH Key to Ed25519 on Ubuntu 22.04

On Ubuntu 22.04 you'll get an SSH error of no mutual signature algorithm unless you change keys or modify PubkeyAcceptedKeyTypes.

Delete Old or Unused Local Git Branches Using grep and xargs

I like cleaning up unused branches and doing it manually can be tedious. Here's a 1 liner you can turn into an alias.

Allow 2+ Users to Be Able to Share a Linux Directory with 2775 vs 0775

This is handy if you have 2 different users deploying code to the same directory, such as a deploy user and CI user.

Using Docker's v2 API to Get a List of Tags with the Help of jq

Docker deprecated their v1 API in September 2022, now we can get a lot more details about each tag using the v2 API.

Counting All Git Commits from All Authors and More with Git Shortlog

This could be handy to see how many people committed to a repo or find out who the recent contributers are.

Beware of Piping Echo into base64 on the Command Line

It will add a new line by default which will change your value, consider using printf instead or at least echo with the -n flag.

git diff Has a Quiet Flag to Halt a Script If a File Was Updated

This can be really handy if you want to do something specific in a shell script only if a file has been changed in git.

Using the Cut Command to Parse a CSV File by Delimiters and Characters

Cut can make quick work out of extracting useful data from CSV files or output that has a pattern of characters or bytes.

Prevent Unset Variables in Your Shell / Bash Scripts with set nounset

This is handy to prevent typos because this option will halt your script as soon as an unset variable is found.

ShellCheck's -x Flag Lets You Source Files without SC1091 Warnings

This is really handy to avoid having to add a source path as a comment or ignore SC1091 every time you source a file.

Test If Your Shell Scripts Are POSIX Compliant with ShellCheck

Even if you're using a Bash shebang you can run ShellCheck with the --shell flag to supply a different shell to check against.

Respecting the cd or exit Pattern Suggested by ShellCheck SC2164

Even if you plan to use set -e it feels like a reasonable idea to add this to most cd commands you use in a script.

Run Parallel Background Commands in Linux and Wait Until They Complete

Sometimes it's useful to run parallel jobs and wait until they all finish before moving on, we can easily do this on the command line.

When to Use Long (Word) or Short (Letter) Command Line Flags?

I tend to use what's in muscle memory for running adhoc commands in a terminal but long flags when writing scripts or documentation.

lcurl Is a Script to Visit a Site Every X Seconds Using curl

This could be handy to use while testing your deployment strategy to make sure you're able to perform zero downtime deploys.

Get the Last Argument of the Last Run Command in Your Shell with $_

This came in handy recently when I wanted to automatically cd into a long git clone path without typing the path again.

Fix a Let's Encrypt Related Expired Root Certificate on an Old Server

If you have a server with OpenSSL 1.0.x you may have been unable to renew your SSL certificates after September 29th 2021.

Using Bash set -x to Help Debug Why a Script Isn't Working

Bash has an x flag or you can use set -x in a script to print a trace of commands and variables. It's really handy!

Temporarily Ignore a Shell Alias by Using a Backslash

If you've aliased a command with extra flags, once in a while it might be useful to run the raw command. Here's 5 ways to do that.

Using FZF to Preview Text Files on the Command Line and within Vim

Here's a video going over how to set up a Shell alias to preview files. It also works out of the box with Vim using the fzf.vim plugin.

I Recently Switched to Zsh and Created a Dotfiles Install Script

I made the switch from Bash to Zsh, and with that I made a dotfiles install script that works on most Linux distros and macOS.

Why You Should Put Braces around Your Variables When Shell Scripting

Braces are often optional but they're almost always worth using for consistency, reducing confusion and using certain features.

Using envsubst to Merge Environment Variables into Config Files

This command is available on Linux and macOC by default and it lets you template out files with ENV vars to create dynamic config files.

A Live Demo of Maintaining 6 Open Source Docker Example Web Apps

I recorded every step of the way when updating a bunch of packages and services. From the idea to tweeting out the end result.

What to Do If You Forgot to Use Sudo on the Command Line and Vim

Here's 2 ways to re-run a previous command. We'll also cover how to edit a root owned file in Vim without needing to run Vim with sudo.

Using FFmpeg to Get an MP3's Duration and 4 Ways to Get the File Size

Here's a Shell script I created to automate a task that used to take a bunch of steps to do manually.

A Shell Script to Keep a Bunch of Dockerized Example Apps Up to Date

In this video we'll go over an example of how writing shell scripts can help save you a lot of time for things you do regularly.

Save and Restore Tmux Sessions across Reboots with Tmux Resurrect

This is a plugin for tmux that persists your sessions, windows, panes and more. It's controlled by hotkeys to save and restore everything.

Bash Aliases to Prepare Recording Videos

A few shell aliases from my dotfiles that help me prepare to record but you can use this concept for other things too.

Shell Script: Yes / No Prompt, Heredoc, in Place Edits and More

In this video we'll go over a practical example of how I used all of these features in a project renaming shell script.

Change a Git Commit in the Past with Amend and Rebase Interactive

In this video we'll go over a few examples ranging from changing the last commit message to rebasing a commit sometime in the past.

Replacing make with a Shell Script for Running Your Project's Tasks

make is a great tool but it has certain characteristics that make it unfriendly for making long commands easier to run.

A Terminal, tmux, Vim and FZF Theme Switching Script written in Python

We'll go over a zero dependency Python 3 script to quickly change themes and toggle dark / light mode for various command line tools.

3 Practical Examples of Using Bash While and Until Loops

We'll go over using curl to poll a site's status code response, check if a process is running and wait until an S3 bucket is available.

Signing and Verifying Git Commits on the Command Line and GitHub

We'll go over signing commits and tags with a GPG key along with sending and receiving GPG public keys to a Keyserver for verification.

Creating and Managing a GPG Key Pair

We'll go over how to create, edit, set a passphrase, revoke, export, backup and restore a GPG key pair.

1 Hour Talk on Creating a Command Line Development Environment

Topics were covered such as using the command line, terminals, shells, scripting, aliases, prompt, history, tmux, Vim, dotfiles and more.

Use Twitter's API and a Few Command Line Tools to Pick a Random Reply

In this video we'll pipe together twarc, jq, sed, sort and head to pick a random reply from a tweet. This could be useful for contests.

Automatic MySQL / PostgreSQL Backups with a Shell Script and Cron Job

In this video, we'll go over both backing up and restoring a database with a few lines of shell scripting and 2 cron jobs.

Detecting If a Directory Is Mounted or Not (Useful for Backup Scripts)

In this video, we'll use the mountpoint command to check if a directory is mounted and improve a backup script to use it.

3 Gotchas with WSL 2 around Disk Space, Memory Usage and Performance

In this video, we'll identify and go over how to fix 3 different WSL 2 issues that'll likely cause you trouble over time.

Using Diff, Process Substitution and Pipes to Solve a Real Problem

In this video, we'll use diff, find, sed, grep, cut and sort together to write a custom Jekyll tag checking Shell script.

A Linux Dev Environment on Windows with WSL 2, Docker Desktop and More

In this video, we'll go over all of the tools I use on Windows and WSL 2 to create a productive development environment.

Wait until Your Dockerized Database Is Ready before Continuing

In this video, we'll go over using a script to make sure your database is ready before running automated tests. Perfect for CI.

Linting and Improving Your Bash Scripts with ShellCheck

In this video we'll go over how ShellCheck can help us find both subtle and obvious bugs / issues with in shell scripts.

Using sed Range Patterns, grep and tr to Parse a Changelog File

In this video, we'll pipe together a few Unix tools to parse out changes from a specific release in a Markdown based changelog file.

Organize Your Text Based Notes from the Command Line with This Script

In this video, we'll go over managing text based notes from the terminal using a zero dependency shell script.

Listing Docker Tags on the Command Line Using a Bash Alias

In this short video we'll go over how to list all Docker tags for a specific image on the Docker Hub using the command line.

Find and Replace Text in 1 or More Files Using Vim, fzf and ripgrep

In this video we'll cover a bunch of different find / replace use cases ranging from simple word searches to regular expressions.

Using tmux Sessions, Windows, Panes and Vim Buffers Together

Here's a short video going over how I switch between a dozen software projects in seconds using nothing but my terminal, tmux and Vim.

Calculate Invoice Amounts with Bash as a Freelance Developer

Keeping track of your billable hours is a tedious task as a freelance or contract worker. How's how you can automate it with Bash.

Using Unix Tools and Bash to Convert Blog Post Titles - Part 2

Combine Bash, grep, sed and Python to title case any number of words. In this example, it is being done on 200+ blog posts.

Using Unix Tools and Bash to Convert Blog Post Titles - Part 1

You can get a lot done using the command line when you combine Bash with a couple of Unix tools. Here's a real world example.

I Tried Linux as My Main Dev Environment but Was Forced Back to Windows

For years I've been running Linux in VMs or WSL but I wanted to give native Linux a shot. It didn't work out due to audio issues.

A Linux Dev Environment on Windows with WSL, Docker, tmux and VSCode

I've spent a full year using WSL and I am still convinced it is the ultimate development environment set up if you use Windows.

Allowing for Errors in Bash When You Have set -e Defined

Using set -e is great for dealing with errors in Bash, but sometimes you want to gracefully handle an error instead of exit immediately.

Here's Why You Should Quote Your Variables in Bash

Technically you don't have to place quotes around your variables but if you ignore doing it, you may encounter unexpected results.

Fuzzy Search Your Bash History in Style with fzf

If you spend a lot of time in a terminal then knowing how to search your history efficiently saves a ton of time. Here's how.

Executing Code after an Error Occurs with Bash When Using set e

I'm sure you're using set -e in your scripts, and often times it's useful to execute some code if an error occurs. Here's how.

Automatic Offline File Backups with Bash and Rsync

Not backing up your files could lead to data loss in the future. Here's how to do offline backups with a few lines of Bash.

Using WSL and MobaXterm to Create a Linux Dev Environment on Windows

The Windows Subsystem for Linux (WSL) is ready for prime time. You no longer need a VM to run graphical Linux apps on Windows.

Do You Need to Be a Linux Wizard to Use Docker as a Developer?

Docker puts you into a great position to manage the full life cycle of your applications, which could naturally lead to being a sys admin.

Who Else Wants to Boost Their Terminal Productivity with tmux?

tmux allows you to save your terminal sessions and split your terminal into multiple windows. It's one of my favorite tools.

Transform a Toshiba Chromebook CB35 into a Linux Development Environment with GalliumOS

Learn how to upgrade and transform a Chromebook to run GalliumOS, which is a native Linux based OS designed for Chromebooks.

Managing Your Passwords on the Command Line in Linux with pass

Learn how to easily encrypt and organize all of your passwords on the command line using a great little program called 'pass'.

Create an Awesome Linux Development Environment in Windows with VMware

Set up a seamless Linux development environment in Windows using the free version of VMware.