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Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Emulate tail using awk.
This awk codes emulates tail. For efficiency it uses a circular array, which stores only N number of records. Using awk gives the flexibility of modifying the output as needed, for example adding the record number (NR) at the output and much more.

Do not clear the screen after viewing a file with less
From the manpage: $ man less -X or --no-init Disables sending the termcap initialization and deinitialization strings to the terminal. This is sometimes desirable if the deinitialization string does something unnecessary, like clearing the screen. Bonus: If you want to clear the screen after viewing a file this way that had sensitive information, hit or just type clear. Since is readily available, I don't know why less bothers to automatically clear. If you're viewing the file at all, chances are you want to see the output from it after you quit.

Sort a character string
Sorts a character string, using common shell commands.

grep for minus (-) sign
Use flag "--" to stop switch parsing

Rename files in batch

On Mac OS X, runs System Profiler Report and e-mails it to specified address.
Replace "user@domain.com" with the target e-mail address. Thanks to alediaz for "$HOSTNAME" which is very useful when running the command with Apple Remote Desktop to multiple machines simultaneously.

most used commands in history (comprehensive)
Most of the "most used commands" approaches does not consider pipes and other complexities. This approach considers pipes, process substitution by backticks or $() and multiple commands separated by ; Perl regular expression breaks up each line using | or < ( or ; or ` or $( and picks the first word (excluding "do" in case of for loops) note: if you are using lots of perl one-liners, the perl commands will be counted as well in this approach, since semicolon is used as a separator

Sniffing network to generate a pcap file in CLI mode on a remote host and open it via local Wireshark ( GUI ).
Then hit ^C to stop, get the file by scp, and you can now use wireshark like this : $ wireshark /tmp/sniff.pcap If you have tshark on remote host, you could use that : $ wireshark -k -i

Perl one-liner to determine number of days since the Unix epoch
There are some environments that use this value for password and account expiration. It's helpful to be able to quickly determine the number of days since the Unix epoch (dse) when working directly with the configuration files as an administrator.


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