Tools/Linux Commands

Linux Commands — Essential CLI Reference

Every essential Linux command organized by category with common flags and one-line descriptions. Built for developers who want CLI fluency.

Navigation & File System

Command	Common flags	Description
`ls`	`-la \| -lh \| --color`	List directory contents
`ls -la`		Long format with hidden files
`cd`	`~ \| - \| ..`	Change directory
`pwd`		Print working directory (current path)
`mkdir`	`-p path/to/dir`	Create directory (and parents with -p)
`rmdir`		Remove empty directory
`rm`	`-rf dir \| -i file`	Remove files or directories
`cp`	`-r src/ dst/ \| -p`	Copy files or directories
`mv`	`src dst`	Move or rename files
`touch`	`file.txt`	Create empty file or update timestamp
`ln`	`-s target link`	Create symbolic or hard link
`tree`	`-L 2`	Display directory tree structure

File Operations & Text

Command	Common flags	Description
`cat`	`file.txt \| -n`	Print file contents to stdout
`less`	`file.log`	Page through file interactively
`head`	`-n 20 file`	Print first N lines of a file
`tail`	`-n 50 -f file.log`	Print last N lines; -f follows in real time
`grep`	`-r -n -i --color pattern .`	Search for pattern in files
`grep -rn`	`"TODO" src/`	Recursive numbered search
`find`	`. -name '*.ts' -type f`	Find files matching criteria
`find . -mtime`	`-7`	Find files modified in last 7 days
`sed`	`'s/old/new/g' file`	Stream editor — substitute text
`awk`	`'{print $1}' file`	Text processing and column extraction
`sort`	`-r -n -k2`	Sort lines of a file
`uniq`	`-c \| -d`	Remove duplicate lines (often piped from sort)
`wc`	`-l -w -c file`	Count lines, words, and characters
`diff`	`-u file1 file2`	Show differences between two files
`chmod`	`+x script.sh \| 644 file`	Change file permissions
`chown`	`user:group file`	Change file owner and group

Process Management

Command	Common flags	Description
`ps`	`aux \| -ef`	List running processes
`top`	`-u username`	Interactive process monitor
`htop`		Enhanced interactive process monitor
`kill`	`-9 PID \| -SIGTERM PID`	Send signal to a process
`killall`	`node`	Kill all processes by name
`pkill`	`-f pattern`	Kill processes matching a pattern
`bg`	`%1`	Resume a stopped job in the background
`fg`	`%1`	Bring a background job to the foreground
`jobs`	`-l`	List background jobs in current shell
`nohup`	`cmd &`	Run command immune to hangups
`lsof`	`-i :3000`	List open files / processes on a port
`strace`	`-p PID`	Trace system calls of a process

Networking

Command	Common flags	Description
`ping`	`-c 4 google.com`	Send ICMP echo requests to test connectivity
`curl`	`-s -X POST -H 'Content-Type: application/json' -d '{}'`	Transfer data with HTTP/HTTPS
`curl -I`	`https://example.com`	Fetch HTTP headers only
`wget`	`-O file.zip https://example.com/file`	Download file from URL
`ssh`	`user@host -p 22 -i key.pem`	Secure shell remote login
`scp`	`-r dir/ user@host:/remote/`	Copy files over SSH
`rsync`	`-avz src/ user@host:dst/`	Sync files efficiently over SSH
`netstat`	`-tuln`	Display network connections and listening ports
`ss`	`-tuln`	Socket statistics (faster netstat replacement)
`ip addr`		Show IP addresses of network interfaces
`nmap`	`-p 80,443 host`	Network port scanner
`traceroute`	`google.com`	Trace packet route to a host
`dig`	`+short example.com MX`	DNS lookup tool
`nc`	`-lvnp 8080`	Netcat — read/write network connections

Package Managers

Command	Common flags	Description
`apt update`		Refresh package index (Debian/Ubuntu)
`apt upgrade`	`-y`	Upgrade all installed packages
`apt install`	`nginx -y`	Install a package
`apt remove`	`--purge nginx`	Remove package and config
`apt-get install`	`-y package`	Install (older apt-get syntax)
`brew install`	`node`	Install package (macOS Homebrew)
`brew update`		Update Homebrew formulae
`brew upgrade`	`node`	Upgrade a Homebrew package
`yum install`	`-y nginx`	Install package (RHEL/CentOS/Fedora)
`dnf install`	`-y package`	Install package (modern Fedora/RHEL)
`snap install`	`--classic code`	Install a snap package

Compression & Archives

Command	Common flags	Description
`tar -czf`	`archive.tar.gz dir/`	Create gzip-compressed tarball
`tar -xzf`	`archive.tar.gz`	Extract gzip tarball
`tar -tzf`	`archive.tar.gz`	List tarball contents without extracting
`zip -r`	`archive.zip dir/`	Create zip archive
`unzip`	`archive.zip -d dest/`	Extract zip archive
`gzip`	`file.txt`	Compress a file in-place (.gz)
`gunzip`	`file.txt.gz`	Decompress a .gz file

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