#Shell

Background jobs and inherited file descriptors

Why & backgrounds execution but doesn't stop output from flooding your terminal.

Dynamic shell variables

Learn variable indirection in Bash with ${!var} syntax. Build context-aware configs, function dispatch, and dynamic variable name resolution.

Redowan Delowar·Jan 11·3 min read

Shell Unix TIL CLI

Running only a single instance of a process

Prevent multiple script instances with file locking. Use flock in Bash, fcntl in Python, and syscall.Flock in Go for single-instance processes.

Redowan Delowar·Dec 31·3 min read

Shell Unix Python Go

SSH saga

Complete SSH setup guide: key pairs, authorized_keys, sshd_config, ssh_config, known_hosts, agent forwarding, and hardening for secure remote access.

Redowan Delowar·Dec 17·4 min read

Shell Unix Networking Security

Discovering direnv

Automate environment variables per directory with direnv. Load .envrc files on entry, unload on exit. Integrate with Python venv and uv workflow.

Redowan Delowar·Oct 2·6 min read

TIL Shell Unix CLI

Bash namerefs for dynamic variable referencing

Master Bash namerefs with declare -n to create dynamic variable references. Build generic functions for arrays and associative arrays without eval.

Redowan Delowar·Sep 20·5 min read

Shell Unix TIL CLI

Shell redirection syntax soup

Complete guide to Bash redirection. Master stdout, stderr, pipes, tee, file descriptors, and shorthand syntax with practical examples for every case.

Redowan Delowar·Sep 12·4 min read

Shell Unix

HTTP requests via /dev/tcp

Make raw HTTP requests with Bash's /dev/tcp file descriptor. Build health check scripts without curl or wget using TCP socket connections.

Redowan Delowar·Aug 8·2 min read

TIL Shell Unix Networking

The *nix install command

Replace mkdir, cp, and chmod with a single install command. Copy files, create directories, and set permissions in one step with GNU coreutils.

Redowan Delowar·Jul 28·2 min read

Shell Unix TIL CLI

Here-doc headache

Avoid here-doc pitfalls when running remote commands via SSH. Learn variable expansion gotchas and simpler alternatives for deployment scripts.

Redowan Delowar·Jul 19·3 min read

Shell Unix DevOps GitHub

I kind of like rebasing

Master git rebase for cleaner commit history. Learn interactive rebasing, squashing commits, and rebasing feature branches onto main with practical examples.

Redowan Delowar·Jun 18·6 min read

git Shell Unix GitHub

Pesky little scripts

Organize custom scripts with comma-prefixed naming. Improve tab completion and eliminate clutter by prefixing script names with special characters.

Redowan Delowar·Oct 29·2 min read

Shell Unix CLI

Dotfile stewardship for the indolent

Manage dotfiles across devices with GNU Stow. Symlink configuration files from git repo to home directory with simple, idempotent commands.

Redowan Delowar·Sep 27·4 min read

Shell Unix TIL CLI

Using DNS record to share text data

Share data via DNS TXT records using dig and base64 encoding. Learn limitations, security concerns, and practical use cases for DNS tunneling.

Redowan Delowar·Jul 17·2 min read

Shell Unix TIL Networking

Unix-style pipelining with Python's subprocess module

Build Unix-style command pipelines in Python using subprocess.run with stdout piping for efficient process chaining and output capture.

Redowan Delowar·Jul 14·5 min read

Python TIL Shell Unix

Implementing a simple traceroute clone in Python

Build a traceroute clone in Python using UDP and ICMP sockets to trace network packet routes and measure hop latency with TTL manipulation.

Redowan Delowar·Jun 1·6 min read

Python Networking Shell Unix

Fixed-time job scheduling with UNIX 'at' command

Schedule one-time commands with UNIX at command. Learn job queuing, remote scheduling via HTTP API, and managing atd/atrun daemons.

Redowan Delowar·May 14·7 min read

Shell Unix JavaScript Networking

Associative arrays in Bash

Learn how to use associative arrays in Bash to create key-value pairs, mimic dictionaries, and manage complex data structures in shell scripts.

Redowan Delowar·May 3·4 min read

Shell Unix TIL Data Structures

Process substitution in Bash

Use process substitution <() to treat command output as files in Bash. Compare directories, process data, and avoid temporary files with this technique.

Redowan Delowar·Apr 30·6 min read

Shell Unix TIL

Dynamic menu with select statement in Bash

Build interactive CLI menus with Bash select statement. Create user-friendly command-line tools with option selection and function dispatch.

Redowan Delowar·Apr 29·3 min read

Shell Unix TIL CLI

Simple terminal text formatting with tput

Format terminal output with tput instead of ANSI codes. Set colors, bold text, underlines, and backgrounds with simple commands in shell scripts.

Redowan Delowar·Apr 23·3 min read

Shell Unix TIL CLI

Tinkering with Unix domain sockets

Build Unix domain socket servers and clients with Python and socat. Access Docker API via UDS, create HTTP servers, and optimize inter-process communication.

Redowan Delowar·Mar 11·7 min read

Python Shell Unix Networking

Colon command in shell scripts

Use the colon : command as a no-op in Bash scripts for cleaner debug output with -x flag. Alternative to echo for section markers and comments.

Redowan Delowar·Dec 23·2 min read

Shell Unix TIL CLI

Auditing commit messages on GitHub

Automate commit message validation with GitHub Actions. Enforce refs and closes patterns to maintain clean Git history and link commits to issues.

Redowan Delowar·Oct 6·5 min read

GitHub DevOps Shell Unix

To quote or not to quote

Master shell quoting rules: single vs double quotes, backticks vs $(). Learn when to quote variables to prevent spaces and special characters from breaking commands.

Redowan Delowar·Oct 5·3 min read

Shell Unix

Returning values from a shell function

Understand how return values work in Bash functions. Learn exit codes, status evaluation patterns, and proper boolean returns with true/false commands.

Redowan Delowar·Sep 25·3 min read

Shell Unix TIL

Distil git logs attached to a single file

View git commit history for a single file with git log --follow. Learn to track multiple files with xargs and concatenate their commit logs.

Redowan Delowar·Jun 21·2 min read

Shell Unix Git TIL

Health check a server with 'nohup $(cmd) &'

Run background health checks in CI with nohup and ampersand. Test server readiness with retry loops and automatic cleanup on success or failure.

Redowan Delowar·Apr 18·2 min read

Shell Unix TIL DevOps

Don't add extensions to shell executables

Why executable scripts shouldn't have extensions. Learn GitHub's scripts-to-rule-them-all pattern for language-agnostic project automation.

Redowan Delowar·Nov 23·1 min read

Shell Unix TIL CLI

Use 'command -v' over 'which' to find a program's executable

Replace which with command -v for POSIX-compliant executable lookup. Learn why command -v is the portable alternative for finding program paths.

Redowan Delowar·Nov 16·1 min read

Shell Unix TIL CLI