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List all information about all files (in current dir)
This is a funny usage of the traditional command ls. It could be basically simplified as: $ ls -a -l Duplicating arguments is permitted: $ ls -a -l -l And this markup could be shortened as: $ ls -al Extra note: To view filesizes like a pro, pray for your God: $ ls -allah

32 bits or 64 bits?

Quickly add a new user to all groups the default user is in
This is a standard procedure for me, whenever I set up a new Raspberry Pi system. Because the default user is "pi", I quickly replace it with my own (e.g. "kostis"), but I have to substitute that user to all of pi's groups first, before deleting the default account. xargs helps a lot with that in a single line, while avoiding boring "for" loops. For everything trickier, there's always "parallel" :)

I finally found out how to use notify-send with at or cron
You can write a script that does this : $remind []

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Check if a domain is available and get the answer in just one line
Returns nothing if the domain exists and 'No match for domain.com' otherwise.

List files
Shortcut to list files in the current path.

'readlink' equivalent using shell commands, and following all links
This is a equivalent to the GNU ' readlink' tool, but it supports following all the links, even in different directories. An interesting alternative is this one, that gets the path of the destination file $ myreadlink() { [ ! -h "$1" ] && echo "$1" || (local link="$(expr "$(command ls -ld -- "$1")" : '.*-> \(.*\)$')"; cd $(dirname $1); myreadlink "$link" | sed "s|^\([^/].*\)\$|$(dirname $1)/\1|"); }

start a VNC server for another user

How to get an absolute value
Whenever we are only interested in difference between two numbers and not the positive/negative values we can use this in script.


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