Which Windows operating system am I running ?

Hummmm if you say so...

Activate/Deactivate wifi on openSUSE asks for administrator password

I was very annoyed by the behavior of Network Manager in openSUSE 12. Every time I want to enable/disable the wifi and want to automatically connect to my prefered wifi spot, the system asks for the administrator password...

This can be changed by editing the file /etc/polkit-default-privs.local and add :

org.freedesktop.NetworkManager.enable-disable-wifi            yes

then run the command :

# set_polkit_default_privs 

So now current logged user can enable or disable the wifi connection without the administrator password... Enjoy.

VIM tips

Vim in read-only mode : view

Did you know that vim has a read-only mode ?
Just use :

# view myfile.txt

Searching for the current word :

In normal mode, move the cursor to any word. Press * to search forwards for the next occurrence of that word, or press # to search backwards.

 Delete "empty" lines : 

Sometime you can be annoyed by "empty" lines which contains no character in your file, to delete them you can use :

:g/^$/d

:g will execute a command on lines which match a regex. The regex is "empty line"  (start with nothing and end with nothing) and the command is :d for delete

Delete "blank" lines : 

Beside "empty" line, you might want to delete lines which contains only whitespaces characters (spaces/tabs) in your file :

:g/^\s*$/d

Visual block editing :

Activate the visual block mode :

CTRL+v

Insert Mode before every line of the block :

SHIFT+i

Apply the insert :

ESC

Process tracking on Linux

Some useful tricks to track a process running in your Linux system.

How to track in real time a specific process by his name :

The top command is very useful to see what's going on in your system, but sometimes there is too much processes monitored, so here is a trick to show only "procname1" and "procname2" in top :

# top -p $(pgrep procname1 | xargs echo | sed -e 's/ /, /g') -p $(pgrep procname2 | xargs echo | sed -e 's/ /, /g')

Example with :

# top -p $(pgrep httpd | xargs echo | sed -e 's/ /, /g') -p $(pgrep nfs| xargs echo | sed -e 's/ /, /g')

How to track any processes waiting for disk I/O :  

# watch -n 1 "(ps aux | awk '\$8 ~ /D/ { print \$0 }')"

Example :

How to find out which processes are swapping  :  

# for i in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $i; done | sort -k 2 -n -r | less

Example :