1.sudo!!: run last command with sudo.
2.Python -m SimpleHTTPServer: simple web page for the current working directory over port 8000.
3.mtr: ping+traceroute.
4.Ctrl+x+e: fires up an editor in the terminal.
5.nl: outputs the content of text file with numbered lines.
6.shuf: randomly selects line/file/folder from a file/folder.
7.ss: outputs socket statistics.
8.last: last logged in users.
9.curl ifconfig.me: shows machine’s external IP Address.
10.tree: lists files and folders in tree like fashion, recursively.
11.pstree: prints running processes with child processes, recursively.
12. command: a space before a bash command, is not recorded in history.
13.stat: shows the status information of a file as well as of a file system.
14..And.: A tweak which put the last command argument at prompt, in the order of last entered command, appearing first.
15.pv: outputs simulating text, similar to hollywood movies.
16.mount | column -t: lists mounted file system, in nice formatting with specification.
17.Ctrl + l: clear shell prompt, instantaneously.
18.curl -u gmail_id –silent “https://mail.google.com/mail/feed/atom” | perl -ne ‘print “\t” if //; print “$2\n” if /(.*)/;’. This simple scripts, opens up, unread mail of an user, in the terminal itself.
19.screen: detach and reattach, long running process from a session.
20.file: outputs information, regarding types of file.
21.id: print user and group id.
22.^foo^bar: run last command with modification, without the need of rewriting the whole command again.
23.>file.txt: flush the content of a text file, in a single go, from the command prompt.
24.at: run a particular command, time based.
25.du -h –max-depth=1: outputs the size of all the files and folders within current folder, in human readable format.
26.expr: Solve simple mathematical calculations from the terminal.
27.look: check for an English word, from the dictionary, in case of confusion, right from the shell.
28.yes: continues to print a sting, till interrupt instruction is given.
29.factor: factors of a decimal number.
30.ping -i 60 -a IP_address : pings the IP_address, and gives audible sound when host comes alive.
31.tac: prints content of a file, in reverse order.
32.strace : A debugging tool.
33.disown -a && exit Command : Run a command in background, even after terminal session is closed.
34.getconf LONG_BIT Command : Output Machine Architecture, very clearly.
35.while sleep 1;do tput sc;tput cup 0 $(($(tput cols)-29));date;tput rc;done & : The script outputs date and time on the top right corner of shell/ terminal.
36.convert : converts the output of a command in picture, automatically.
37.watch -t -n1 “date +%T|figlet” : Show animated digital clock at the prompt.
38.host and dig : DNS lookup utility.
39.dstat : Generates statistics regarding system resource.
40.bind -p : Shows all the shortcuts available in Bash.
41.Touch /forcefsck : Force file-system check on next boot.
42.lsb_release : Prints distribution specification information.
43.nc -ZV localhost port_number : Check if a specific port is open or not.
44.curl ipinfo.io : Outputs Geographical Information, regarding an ip_address.
45.find .-user xyz : Lists all file owned by user ‘xyz’
46.apt-get build-dep package_name: Build all the dependency, automatically while installing any specific package.
47.lsof -iTCP:80 -sTCP:LISTEN. The script, outputs all the service/process using port 80.
48.find -size +100M : This command combination, Lists all the files/folders the size of which is 100M or more.
49.pdftk : A nice way to concatenate a lot of pdf files, into one.
50.ps -LF -u user_name : Outputs Processes and Threads of a user.
51.Startx — :1 (This command creates another new X session).