Change directory quickly with cd
cd navigates the working directory; use -, ~ and pushd/popd for convenience.
Quick references
Small things worth keeping
61 compact commands and observations collected while building software. They are intentionally short and written to be useful again without a long introduction.
Shell and Unix
Commands and shell behavior kept as a concise working reference.
Change permissions with chmod
Set file permissions using chmod; octal and symbolic modes available.
Check disk free space with df
Use df to show disk free space; -h shows human-readable sizes.
Check disk usage with du
du reports directory and file sizes; use -sh for human-readable summaries.
Clear the terminal
Clear the terminal with clear or control-L, and reset a terminal that is in a bad state.
Control resources with ulimit
Use ulimit to set resource limits for shells and processes.
Coprocess communication with coproc
Use coproc to run a process and communicate with it via file descriptors.
Create directories with mkdir
Use mkdir -p to create nested directories safely from scripts.
Download with wget
Quick wget examples for downloading files and resuming partial downloads.
Export environment variables
export makes variables available to child processes; assign then export or do both on one line.
Formatted output with printf
Use printf for predictable, formatted output instead of echo.
Here-strings (<<<)
Here-strings (`<<<`) feed a short string as stdin to a command.
Lint shell scripts with shellcheck
Use shellcheck to find common shell scripting mistakes.
Quickly view file contents
Use cat, less, more to view file contents; tail -f follows logs.
Remove a file with rm
Use rm to remove files; consider safer alternatives interactively.
Reverse-search history
Use Ctrl+R to reverse-search your shell history interactively.
Search text quickly with grep
Use grep for pattern search; -R to recurse, -n for line numbers, -i for ignore-case.
Secure copy with scp
Copy files over SSH using scp; consider rsync for complex syncs.
Show bash version
Display Bash version and release info.
Show first lines with head
head prints the first N lines of a file; combine with tail or sed for ranges.
Show last lines with tail
Use tail to show last lines or follow a growing file.
Show listening sockets with ss
ss inspects sockets; use -ltnp to list TCP listening ports with processes.
Sort and dedupe lines
Sort lines and remove duplicates with sort and uniq; use -V for version-aware sorting.
Source a script into the current shell
Use `source` or `.` to run a script in the current shell so it can set variables/functions.
Stream edit files with sed
sed performs text transforms in a stream; safe inline edits with backups.
Subshells vs grouping
Use ( ) for subshells and { } for grouping commands in the current shell.
Substitute environment variables in templates with envsubst
Use envsubst to replace $VAR placeholders in templates safely.
Sync with rsync
Use rsync for efficient, resumable synchronization; -a preserves attributes.
Today I Learnt: Arithmetic evaluation
Perform arithmetic inside bash scripts with $(( )) or let.
Today I Learnt: Change file owner with chown
Change owner and group of a file.
Today I Learnt: Change process priority with nice and renice
Start a process with lower priority using nice.
Today I Learnt: Check memory with free
Use free -h to inspect system memory usage.
Today I Learnt: Compare files with cmp
Use cmp to compare two files byte-by-byte.
Today I Learnt: Copy files with cp
Use cp to copy files and directories.
Today I Learnt: Create an empty file with touch
Create or update file timestamps with touch.
Today I Learnt: Create named pipes with mkfifo
Use FIFOs to connect unrelated processes.
Today I Learnt: Extract dirname from a path
Use dirname to get the directory component of a path.
Today I Learnt: Fetch a URL with curl
Use curl to download or interact with HTTP endpoints.
Today I Learnt: Find files with find
Search for files by name, type, size, and more using find.
Today I Learnt: Interactive menus with select
Use select to build simple interactive menus in bash scripts.
Today I Learnt: List files with ls
Quick: list files including hidden and permissions.
Today I Learnt: Move or rename files with mv
Move or rename files using mv.
Today I Learnt: Pause with sleep
Sleep for a number of seconds.
Today I Learnt: Print environment variables
Show environment variables and inspect PATH.
Today I Learnt: Print working directory with pwd
Show current directory.
Today I Learnt: Process substitution to treat commands like files
Use <(...) or >(...) to pass command output or input as a filename.
Today I Learnt: Read user input in bash
Prompt and read input into a variable with read.
Today I Learnt: Show command history with history
List recent shell commands.
Today I Learnt: Show system info with uname
Print kernel and OS information.
Today I Learnt: Trap signals and cleanup
Use trap to run cleanup on EXIT or signals.
Today I Learnt: Use flock for atomic file locking
Use flock to prevent concurrent script runs from clobbering files.
Engineering and project work
Small observations about tools, communication, project evidence, and delivery.
Today I Learnt: Getting Started with Oso Authorization in Node.js
How to add policy-based authorization using Oso in a Node.js app with a minimal example.
Today I Learnt: LinkedIn for Engineers — Practical Personal Branding
Small LinkedIn habits that make your profile and posts discoverable to recruiters and potential clients.
Today I Learnt: Optimizing Your GitHub Profile for Recruiters
Make your GitHub profile and repos speak for you: README, pinned projects, issues, and contributions.
Today I Learnt: Portfolio Structure That Gets Recruiter Attention
A lean portfolio structure to showcase work, skills, and contact channels for recruiters and clients.
Today I Learnt: Show Impact — Metrics That Recruiters and Clients Care About
Which metrics to show on your portfolio and how to present them so they communicate value quickly.
Today I Learnt: Technical Blogging for SEO and Visibility
Practical SEO tips for technical bloggers who want organic traffic and recruiter discovery.
Today I Learnt: Technical Storytelling — Make Your Work Memorable
How to tell the story of your technical work so recruiters and clients remember you.
Today I Learnt: Use Open Source to Get Noticed by Recruiters
How contributing to open source can surface you to recruiters and how to do it efficiently.
Today I Learnt: Write Winning Technical Proposals Quickly
A fast, repeatable proposal template to win freelance clients without over-engineering.
Today I Learnt: Writing Project Case Studies That Sell
How to write concise project case studies that highlight impact and attract clients or recruiters.