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Print a great grey scale demo !
Seen here: http://www.pixelbeat.org/docs/terminal_colours/

switch case of a text file

Force the script to be started as root
Place this code at the beginning of your script to ensure that it can only be executed by the root.

Calculate pi with specific scale
a() function in bc is for arctangent, available if using -l option included.

network interface and routing summary

ssh autocomplete
Autocomplete from .ssh/config

Changing the terminal title to the last shell command
You can set the previous bash command as the terminal title by this command. Explanation: -trap assigns a command to execute at a given bash signal. -in the $BASH_COMMAND you find the last command -you can set the terminal title with the escape sequence: \e]0;this is the title\007 -to let the echo care about the backslashes give the -e to it Since trap is a built in bash command you find more informatin in 'man bash'for more Source: http://www.davidpashley.com/articles/xterm-titles-with-bash.html

prevent large files from being cached in memory (backups!)
We all know... $ nice -n19 for low CPU priority.   $ ionice -c3 for low I/O priority.   nocache can be useful in related scenarios, when we operate on very large files just a single time, e.g. a backup job. It advises the kernel that no caching is required for the involved files, so our current file cache is not erased, potentially decreasing performance on other, more typical file I/O, e.g. on a desktop.   http://askubuntu.com/questions/122857 https://github.com/Feh/nocache http://packages.debian.org/search?keywords=nocache http://packages.ubuntu.com/search?keywords=nocache   To undo caching of a single file in hindsight, you can do $ cachedel   To check the cache status of a file, do $ cachestats

List all Samba user name

for newbies, how to get one line info about all /bin programs
Get simple description on each file from /bin dir, in list form, usefull for newbies.


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