Shell is also called command line interface, it is the interface between *nix users and computer. Shell is a program which provides service to access OS kernel services.
This article is to introduce some not so well known but useful and interesting knowledge about shell.
Wiki
- shell was born almost at the same time as Unix. The first UNIX shell was written by Ken Thompson in 1971 and its name is Thompson sh. It's older than Linux kernel.
- The default Shell in most *nix and MacOS is bash, bash was created by Brian Fox in 1987, the full name is Bourne Again shell(bash).
- There are other shells except bash, there are Bourne shell(sh), Korn shell(ksh), C shell(csh). Actually there are over 50 different shells. For details , please refer : http://www.freebsd.org/ports/shells.html
Some powerful commands
We strongly recommend that you open a shell prompt console to try these commands.
!$
!$ is a special environment variable, it represents the last string of last command. For example:
$mkdir mydir
$mv mydir yourdir
$cd yourdir
You can modify it as:
$mkdir mydir
$mv !$ yourdir
$cd !$
sudo !!
Execute the previous command with root role.
For example:
In Ubuntu, it needs root role when using apt-get to install packages, we may often forget to add sudo before apt-get. So everytime we may need to add sudo and then type this command again, actually we can use sudo !! to complete this easily.(Edited by Hao Chen : In shell, sometimes you may type a long command, you can use !XXX to repeat last command, for example, you might type vi /where/the/file/is, next time you can use !vi to repeat the vi command.
cd -
Back to the previous directory you accessed. For example: The current working directory is /home/a, then you use cd ../b to go to /home/b, now you can use cd - to switch between /home/a and /home/b forth and back.
'ALT+.' or '.'
Hot key alt+. or esc+. can bring back the options of last command
^old^new
Replace some characters in previous command
For example :
echo "wanderful", actually you may want to output echo "wonderful". Then you only need ^a^o. It's very useful when you want to modify a very long command just because some spell errors. (Edited by Hao Chen :You can also use !!:gs/old/new)
du -s * | sort -n | tail
List the biggest 10 files in current directory
:w !sudo tee %
Save a file which can only be writable with root permission in vi.
date -d@1234567890
Covert timestamp to date
> file.txt
Create an empty file
mtr coolshell.cn
mtr is better than traceroute
Add an empty space before a command, this command will be in the history list.
echo “ls -l” | at midnight
execute a command at some time
curl -u user:pass -d status=”Tweeting from the shell” http://twitter.com/statuses/update.xml
Update Twitter in command line
curl -u username –silent “https://mail.google.com/mail/feed/atom” | perl -ne ‘print “\t” if //; print “$2\n” if /<(title|name)>(.*)<\/\1>/;’
Check your unread mails in Gmail
ps aux | sort -nk +4 | tail
List top 10 processes which consume most memory
man ascii
Show the ASCII chart
ctrl-x e
Launch default editor quickly (It is set by $EDITOR)
netstat –tlnp
List the port number which local host processes listen to
tail -f /path/to/file.log | sed '/^Finished: SUCCESS$/ q'
Quit tail when "Finished: SUCCESS" appears in the file.log file, this command is used to check and filter some records in log in real time.
ssh user@server bash < /path/to/local/script.sh
Execute a script in a remote machine. The best thing about this command is there is no need to copy the script to the remote machine.
ssh user@host cat /path/to/remotefile | diff /path/to/localfile -
Compare a local file with a remote file
net rpc shutdown -I ipAddressOfWindowsPC -U username%password
Shutdown a remote windows machine
wget --random-wait -r -p -e robots=off -U mozilla http://www.example.com
Download the whole example.com website
curl ifconfig.me
When you are in an intranet, you can use this command to check IP on internet.
convert input.png -gravity NorthWest -background transparent -extent 720×200 output.png
Resize a picture
lsof –i
Check network service status
vim scp://username@host//path/to/somefile
vim a remote file
python -m SimpleHTTPServer
One command to realize HTTP service, set the current directory as HTTP service directory. You can use http://localhost:8000 to access it. This may be the simplest HTTP server on the planet.
history | awk '{CMD[$2]++;count++;} END { for (a in CMD )print CMD[a] " " CMD[a]/count*100 "% " a }' | grep -v "./" | column -c3 -s " " -t | sort -nr | nl | head -n10
This command will list the top 10 most frequently used commands
You can also refer to another artciel for more useful Linux commands: Concise bash programming skills.
Author :404null Source : http://coolshell.cn/articles/8619.html
