# Unix

> Expert guidance on Unix operating system commands and administration. Use for: file system operations, process management, text processing, networking, shell scripting, user management, permissions, environment configuration, system monitoring, and automation.

- Skill: `neuralblitz/unix` (Agent Skill)
- Install (CLI): `npx skillmds@latest add neuralblitz/unix`
- Raw SKILL.md: https://api.skillmd.com/api/skills/neuralblitz/unix/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: MIT
- Author: NeuralBlitz (https://skillmd.com/u/neuralblitz)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/neuralblitz/unix

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# Unix & Linux — Command Reference

Covers: **File Operations · Process Management · Text Processing · Networking · Scripting · System Administration**

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## File System Operations

### File Navigation and Listing

The Unix file system follows a hierarchical tree structure with the root directory "/" at the top. Understanding how to navigate this structure efficiently is fundamental to working with Unix systems. Modern Unix systems maintain a consistent directory structure following the Filesystem Hierarchy Standard (FHS).

Common directories include: /bin for essential binaries, /etc for system configuration, /home for user directories, /var for variable data like logs, /tmp for temporary files, /usr for user programs, and /proc for process information.

```bash
# Basic navigation
cd /home/user/projects          # Change directory
cd ~                           # Go to home directory
cd -                           # Go to previous directory
pwd                            # Print working directory
ls                             # List files
ls -la                         # List all files with details
ls -lh                         # Human-readable file sizes
ls -lt                         # Sort by modification time
ls -lS                         # Sort by file size
ls -R                          # Recursive listing
ls -1                          # One file per line
ls -d */                       # List directories only

# Using ls with various options
ls -a                          # Show hidden files (starting with .)
ls -A                          # Show hidden files except . and ..
ls -F                          # Append file type indicators (* / @ |)
ls --color=auto                # Colorize output by type

# Advanced listing
ls -l | grep '^d'              # List directories only
ls -l | awk '{print $9}'       # List just filenames
ls -t | head -n 10             # 10 most recently modified files
find . -type f -ls             # Detailed listing with find
```

### File Creation and Manipulation

```bash
# Create files
touch newfile.txt              # Create empty file
touch -t 202312251200 file     # Create with specific timestamp
echo "content" > file.txt      # Create with content (overwrite)
echo "content" >> file.txt     # Append content
printf "Line1\nLine2\n" > f    # Create with newlines
cat > file.txt << EOF          # Here-document creation
Multi-line
content
here