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Find the package that installed a command

Convert any sequence of spaces/tabs to single space/tab
Remove empty lines additionally: $ tr -s ' \t\n' 2.txt identical with: $ tr -s '[:space:]' 2.txt To "clean perfectly" a text or code file, You can combine this command with another one: $ while read l; do echo -e "$l"; done 2.txt (= remove all leading and trailing spaces or tabs from all lines of a text file)

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"

convert hex to decimal ; decimal to hex

Empty Bind9 cache
Occasionally, to force zone updating, cache flush is necessary. The use of this command is better than restart the Bind9 process.

Remove specific entries from iptables
Then you can remove the specific entry: iptables -D INPUT 10 Just make sure these are set: IPTABLES_SAVE_ON_STOP="yes" IPTABLES_SAVE_ON_RESTART="yes" Else your changes won't stick when you restart iptables.

Broadcast your shell thru port 5000
Doesn't work so well if you connect from windows. Linux only sends LF where windows wants CRLF. The alternative command works better with windows, however it uses script and a named pipe.

Search for a process by name
ps and grep is a dangerous combination -- grep tries to match everything on each line (thus the all too common: grep -v grep hack). ps -C doesn't use grep, it uses the process table for an exact match. Thus, you'll get an accurate list with: ps -fC sh rather finding every process with sh somewhere on the line.

List the most recent dates in reverse-chronological order
bash brace expansion, sequence expression

Edit 2 or more files in vim using vim -d
Use vim's diff mode to edit two or more files in one window. The '+diffoff!' turns off diff highlighting when the session is started. Use ctrl+w + ctrl+w to switch between windows.


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