Essential Linux Command‑Line Tips and Tricks for Efficient System Use

1. Basic Commands

Familiarize yourself with core Bash concepts, read the full man page, and master VIM as a powerful editor.

Learn SSH key‑based authentication using ssh-agent and ssh-add, for example:

#!/bin/sh
scp ~/.ssh/id_dsa.pub $1@$2:~/
ssh $1@$2 "touch ~/.ssh/authorized_keys ; cat ~/id_dsa.pub >> ~/.ssh/authorized_keys; chmod 644 ~/.ssh/authorized_keys; exit"

Know common task‑management shortcuts such as &, Ctrl‑Z, Ctrl‑C, jobs, fg, bg, kill, and essential file‑handling commands like ls, chmod, chown, du, df, mount.

Basic network tools include ifconfig, dig, and regular‑expression utilities such as grep with options -o, -A, -B. Package installation uses apt‑get or yum.

2. Useful Bash Expressions

Quick command recall: !! repeats the last command, !$ expands to the last argument, {a..b} generates a numeric range, and {a,b,c} expands to a list of strings.

Parameter expansions include ${1‑9} for script arguments, $0 for the script name, $# for argument count, $? for the previous exit status, $$ for the current PID, and $* for all arguments.

3. Daily Command‑Line Tools

Search command history with Ctrl‑R. Editing shortcuts: Ctrl‑W deletes the previous word, Ctrl‑U clears the line, Alt‑BackSpace deletes the word before the cursor.

Navigate directories with cd - to return to the previous location.

Powerful utilities include xargs (e.g., find . -name *.py | xargs grep some_function), parallel for parallel execution, pstree -p to view process trees, pgrep / pkill for name‑based process control, and session managers like screen, tmux, dtach.

Network inspection with lsof, netstat -lntp, and debugging with set -x (trace) or set -e (exit on error). Use a semicolon to run commands in a subshell: (cd /some/other/dir; other‑command).

Shell parameter tests such as ${name:?error message} and substring removal ${var%suffix}, ${var#prefix} are also covered.

Redirection examples: some_command > logfile 2>&1 and input‑output tricks like <tab> via Ctrl‑V or $'\t'.

4. Data Processing

Sorting and deduplication with sort, uniq, uniq -u, uniq -d. Text manipulation tools include cut, paste, join, and set operations using pipelines, e.g.:

cat a b | sort | uniq > c   # union
cat a b | sort | uniq -d > c   # intersection
cat a b b | sort | uniq -u > c   # difference

Set locale to LC_ALL=C for faster sorting. Use awk for column calculations ( awk '{ x += $3 } END { print x }'), sed for in‑place edits, shuf to randomize lines, and sort -k with stable option -s for multi‑field sorting.

Binary file utilities: hd, bvi, strings, grep, and encoding converters iconv / uconv. Splitting files with split or csplit.

5. System Debugging

Performance and resource monitoring with iostat, netstat, top, htop, dstat, free, vmstat. Generate Java stack traces using kill -3 <pid>.

Network diagnostics via mtr, traceroute, iftop, nethogs. Load testing with ab or siege. Deep packet inspection with wireshark or tshark.

Trace system calls with strace and library calls with ltrace; both support profiling ( -c) and attaching to processes ( -p). Inspect shared libraries via ldd and debug binaries with gdb. The /proc filesystem provides runtime information (e.g., /proc/cpuinfo, /proc/XXX/fd).

Historical performance with sar, advanced profiling with stap or perf, and kernel messages via dmesg.

SSH tunneling shortcuts ( ssh -L, ssh -D) and configuration tweaks ( TCPKeepAlive=yes, ServerAliveInterval=15, StrictHostKeyChecking=no, Compression=yes, ForwardAgent=yes) help maintain stable remote sessions.

Finally, the article notes that adding a leading # (via Alt‑#) comments out a partially typed command, preserving it in history for later reuse.