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Find last reboot time
Specific to OSX.

Adding Prefix to File name
Good old bracket expansion :-) For large numbers of files, "rename" will spare you the for-loop, or the find/exec...

Calculates the number of physical cores considering HyperThreading in AWK
Check whether hyperthreading is enabled or not. a better solution as nproc should work on all OS with awk

du and sort to find the biggest directories in defined filesystem
I had the problem that our monitoring showed that the "/" filesystem is >90% full. This command helped me to find out fast which subdirs are the biggest. The system has many NFS-mounts therefore the -x.

Do some Perl learning...
Prerequisites: module Pod::Webserver installed. You can install it typing: $ sudo perl -MCPAN -e 'install Pod::Webserver' You can replace elinks with your fav browser. For FF: $podwebserver& sleep 2; firefox -remote 'openurl( http://127.0.0.1:8020/, new-tab )' If you have Firefox open, this will pop-up the index web in a new tab.

Display the inodes number of /

Get a qrcode for a given string

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"

Find out the starting directory of a script
Invoked from within a shell script, this will print the directory in which the script resides. Doesn't depend on external tools, /proc/self/*, etc.. (`echo` is a shell builtin.) To see the *current working* directory of a script, use `pwd`.

Lookup autonomous systems of all outgoing http/s traffic


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