Cheatsheet - command line

Cheatsheet - Command line

The Art of Command line

This guide is for both beginners and experienced users, focusing on breadth, specificity, and brevity. Every tip is essential in some situation or significantly saves time. Written for Linux, it includes sections for macOS and Windows. The focus is on interactive Bash, though many tips apply to other shells and scripting. It includes both standard Unix commands and those requiring special package installs.

Basics

• Bash Fundamentals: Learn basic Bash by typing man bash and skimming it. Bash is powerful and always available.
• Text Editors: Learn at least one text-based editor well, such as nano for simplicity or vim for power users.
• Documentation: Use man for official documentation and apropos to find man pages. Know about Bash built-ins and use help and help -d for help.
• Shell Features: Learn about redirection (>, >>, <), pipes (|), and file glob expansion (*, ?, [ ]).
• Job Management: Be familiar with Bash job management (&, ctrl-z, ctrl-c, jobs, fg, bg, kill).
• SSH: Know ssh and passwordless authentication via ssh-agent and ssh-add.
• File Management: ls, less, head, tail, ln, chown, chmod, du, df, mount, fdisk, mkfs, lsblk.
• Network Management: ip or ifconfig, dig, traceroute, route.
• Version Control: Use a version control system like git.
• Regular Expressions: Know regular expressions and grep options (-i, -o, -v, -A, -B, -C).
• Package Management: Use apt-get, yum, dnf, or pacman to install packages and pip for Python-based tools.

Everyday Use

• Command Line Navigation:
  • Tab for command completion.
  • ctrl-r for command history search.
  • ctrl-w to delete the last word.
  • ctrl-u to delete from the cursor to the start of the line.
  • alt-b and alt-f to move by word.
  • ctrl-a to move to the start of the line.
  • ctrl-e to the end.
  • ctrl-k to kill to the end of the line.
  • ctrl-l to clear the screen.
• Editing Commands: For editing long commands, use ctrl-x ctrl-e to open the current command in an editor.
• Command History: Use history to see recent commands and !n to execute again.
• Process Management:
  • xargs for powerful command-line processing.
  • pstree -p for process tree display.
  • pgrep and pkill to find or signal processes by name.
  • nohup or disown for background processes to run forever.
  • netstat -lntp or ss -plat to see listening processes.
• Shell Customization:
  • alias to create shortcuts for commands and save them in ~/.bashrc.
  • ~/.bash_profile for environment variables and login commands.
  • Synchronize configuration files with Git.
• Scripting Best Practices:
  • Handle whitespace in variables and filenames carefully.
  • Use set -x for debugging output.
  • Use strict modes (set -e, set -u, set -o pipefail) for error handling.
• Advanced Shell Features:
  • Use subshells for temporary directory changes.
  • Use variable expansion, brace expansion, and process substitution.
• Session Management: Use screen or tmux for screen multiplexing and session persistence.
• SSH Optimization: Optimize SSH configuration for better performance and security.

Processing Files and Data

• File Finding: Use find and locate to find files.
• Advanced Searching: Use ack, ag, or rg for advanced searching.
• Document Conversion: Use pandoc for document conversion and xmlstarlet for XML.
• Structured Data: Use jq for JSON and csvkit for CSV files.
• Text Manipulation: Use sort and uniq for text file manipulation.
• Data Munging: Use awk and sed for simple data munging.
• File Copying: Use rsync for fast and versatile file copying.
• Progress Monitoring: Use pv or dd status=progress for monitoring file processing.
• Randomization: Use shuf to shuffle or select random lines from a file.
• File Splitting: Use split and csplit for splitting files.
• Encoding Conversion: Use iconv or uconv for text encoding conversion.
• File Attributes/Permissions: Use chattr for file attributes and getfacl/setfacl for file permissions.

System Debugging

• Web Debugging: Use curl and httpie for web debugging.
• System Status:
  • top, htop, iostat, and iotop for CPU and disk status.
  • netstat and ss for network connection details.
  • dstat and glances for system overviews.
  • free and vmstat for memory status.
• Network Issues: Use mtr for network issues and ncdu for disk usage.
• Bandwidth Usage: Use iftop or nethogs for bandwidth usage.
• System Call Debugging: Use strace and ltrace for system call debugging.
• Live Problem Debugging: Use /proc for live problem debugging.
• Historic Statistics: Use sar for historic system statistics.
• Deeper Analysis: Use stap, perf, and sysdig for deeper system analyses.

One-liners

• Text File Operations: Use sort and uniq for set operations on text files.
• JSON Processing: Use jq for JSON pretty-printing and comparison.
• File Examination: Use grep and head to quickly examine file contents.
• Summing Numbers: Use awk for summing numbers in a text file.
• Recursive Listing: Use find for recursive file listing.
• Tallying Values: Use egrep and sort for tallying values in a text file.
• Continuous Monitoring: Use watch to monitor changes continuously.

Obscure but Useful

• Arithmetic/Boolean: expr
• Macro Processing: m4
• Repetitive Printing: yes
• Calendar: cal
• Running Commands: env
• Data Manipulation: cut, paste, join
• Text Formatting: fmt, pr, fold
• Tab/Space Conversion: expand, unexpand
• Line Numbering: nl
• Number Printing: seq
• Calculations: bc
• Integer Factorization: factor
• Encryption/Signing: gpg
• Network Debugging/Transfer: nc, socat
• Data Moving: dd
• File Type Identification: file
• Directory Display: tree
• File Info: stat
• Command Timing: time
• Command Execution Limits: timeout
• Semaphore Files: lockfile
• Log Management: logrotate
• Repeated Command Execution: watch
• File Change Monitoring: when-changed
• Reverse File Printing: tac
• File Comparison: comm
• Text Extraction: strings
• Character Translation: tr
• Text Encoding Conversion: iconv, uconv
• File Splitting: split, csplit
• Read/Write Same File: sponge
• Unit Conversions: units
• Password Generation: apg
• File Compression: xz
• Dynamic Library Info: ldd
• Symbol Extraction: nm
• Web Server Benchmarking: ab, wrk
• System Call Debugging: strace
• Network Debugging: mtr
• Concurrent Shell: cssh
• File Synchronization: rsync
• Packet Capture: wireshark, tshark
• Network Layer Grep: ngrep
• DNS Lookups: host, dig
• Process File Descriptors: lsof
• System Statistics: dstat, glances
• Disk Usage Stats: iostat
• CPU Usage Stats: mpstat
• Memory Usage Stats: vmstat
• Improved Top: htop
• Login History: last
• Logged-on Users: w
• User/Group Identity: id
• Historic System Stats: sar
• Network Utilization: iftop, nethogs
• Socket Statistics: ss
• Boot/System Error Messages: dmesg
• Kernel Parameters: sysctl
• Disk Manipulation: hdparm
• Block Device Listing: lsblk
• Hardware Info: lshw, lscpu, lspci, lsusb, dmidecode
• Kernel Module Info: lsmod, modinfo
• Fun: fortune, ddate, sl

macOS only

• Package Management: Use brew or port.
• Clipboard Operations: Use pbcopy and pbpaste.
• Terminal Configuration: Enable the Option key in Terminal for alt key functionality.
• Opening Files: Use open to open files with desktop apps.
• File Searching: Use mdfind for file searching and mdls for metadata listing.
• BSD Unix Differences: Be aware of BSD Unix differences and use sw_vers for release info.

Windows only

• Unix Tools: Use Cygwin, WSL, MinGW, or Cash for Unix tools.
• System Administration: Use wmic.
• Networking: ping, ipconfig, tracert, netstat.
• Windows Tasks: Use Rundll32 for various Windows tasks.
• Command-line Window: Use mintty.
• Opening Files: Use cygstart to open files.
• Windows Registry: Use regtool for Windows registry access.
• Path Conversion: Use cygpath for path conversion.