Sort IP Address

There is time you need to sort IP address in the way human understand.

# sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 addresses.txt

Where,

• -t . : Set field to . (dot) as our IPs separated by dot symbol
• -n : Makes the program sort according to numerical value
• -k opts: Sort data / fields using the given column number. For example, the option -k 2 made the program sort using the second column of data. The option -k 3,3n -k 4,4n sorts each column. First it will sort 3rd column and then 4th column.

Report A Snapshot of Current Processes

ps [options]

ps displays information about a selection of the active processes. It accepts several kinds of options:

1. UNIX options, which may be grouped and must be preceded by a dash.
2. BSD options, which may be grouped and must not be used with a dash.
3. GNU long options, which are preceded by two dashes.

 To see every process on the system using standard syntax:

ps -eps -efps -eFps -ely

 To see every process on the system using BSD syntax:

ps axps axu

 To print a process tree:

ps -ejHps axjf

 To get info about threads:

ps -eLfps axms

 To get security info:

ps -eo euser,ruser,suser,fuser,f,comm,labelps axZps -eM

 To see every process running as root (real & effective ID) in user format:

ps -U root -u root u

To see every process with a user-defined format:

ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,commps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,commps -eopid,tt,user,fname,tmout,f,wchan

Print only the process IDs of syslogd:

ps -C syslogd -o pid=

Print only the name of PID 42:

ps -p 42 -o comm=

Shows Exit Code of Previous Command in zsh

To display the exit code of the previous command is very useful in zsh.

PS1='%n%m %~ %(?..[%?] )%# '

%(?..[%?] )
It's a conditional expression. The part before the 1st dot is the expression; the part between the two dots is output if it's TRUE (or 0); the part after the second dot is output if it's FALSE (or any number but 0).

See my full customization on .zshrc file.

Tips on GNU Screen

GNU Screen is a simple but powerful terminal multiplexer.

Two basic commands that I use often:

• screen -r : Re-attach the only-one screen session.
• screen -ls : To show running sessions 

Here's the features that I use often:

• ctrl-a + d : To detach the terminal.
• ctrl-a + c : To create a new terminal
• ctrl-a + p : To switch to the previous terminal
• ctrl-a + n : To switch to the next terminal

Here's the features that I use less often:

• ctrl-a + x : To lock the current terminal
• ctrl-a + S : To split the terminal to two separate areas/tabs.
• ctrl-a + X : To close the current area/tab.
• ctrl-a + [tab] : To switch to the next tab.
• ctrl-a + H : To create a running log of the session.

Advanced usages:

• ctrl-a + M : To start/stop monitor for activity
• ctrl-a + _ : To start/stop monitor for silence 
• ctrl-a + " : To quickly go to that window

References:

• http://polishlinux.org/howtos/screen-tips-tricks/
• http://www.softpanorama.org/Utilities/screen.shtml
• https://wiki.archlinux.org/index.php/GNU_Screen
• http://www.rackaid.com/blog/linux-screen-tutorial-and-how-to/

Tips:

In you accidentally press "ctrl-a s" (instead of "ctrl-a S") while creating tab, which freeze the parent terminal, just press "ctrl-a q" to unfreeze it. 

Some Tricks in using zsh

These are part of the tricks that I like most about zsh:

ESC-. [ Escape period ]
Inserts the last argument of the previous history line, repeat to go back in history.

ESC-'  [ Escape single-quote ]
To quotes the whole line. (Useful for su -c or ssh).

ESC-q [ Escape q ]
To clears the line and inserts it again on the next prompt, allowing you to issue an interim command.

ESC-RETURN [ Escape ENTER ]
To inserts a literal newline, so you can edit longer commands easily.

References:

• http://chneukirchen.org/blog/archive/2008/02/10-zsh-tricks-you-may-not-know.html
• http://www.rayninfo.co.uk/tips/zshtips.html
• http://grml.org/zsh/zsh-lovers.html