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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"

Top 10 requestors by IP address from Apache/NCSA Logs

Run a command if file/directory changes
Example: $ runonchange /etc/nginx nginx -t Ignores vim temp files. Depends on 'inotify-tools' for monitoring of file changes. Alternative to tools like 'entr', 'watchr'.

Do one ping to a URL, I use this in a MRTG gauge graph to monitor connectivity

function to verify an IP address - can be used at the shell prompt or in a shell script
When processing IP addresses in the shell (or shell script) it is useful to be able to verify that the value of data is an IP address (an not some random string or non-sensible IP address).

Print every Nth line
Sometimes commands give you too much feedback. Perhaps 1/100th might be enough. If so, every() is for you. $ my_verbose_command | every 100 will print every 100th line of output. Specifically, it will print lines 100, 200, 300, etc If you use a negative argument it will print the *first* of a block, $ my_verbose_command | every -100 It will print lines 1, 101, 201, 301, etc The function wraps up this useful sed snippet: $ ... | sed -n '0~100p' don't print anything by default $ sed -n starting at line 0, then every hundred lines ( ~100 ) print. $ '0~100p' There's also some bash magic to test if the number is negative: we want character 0, length 1, of variable N. $ ${N:0:1} If it *is* negative, strip off the first character ${N:1} is character 1 onwards (second actual character).

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

open path with your default GNOME program
Another step to bring cli and gui closer together: gnome-open It opens a path with the default (gui) application for its mime type. I would recommend a shorter alias like alias o=gnome-open More examples: $ gnome-open . [opens the current folder in nautilus / your default file browser] $ gnome-open some.pdf [opens some.pdf in evince / your default pdf viewer] $ gnome-open trash:// [opens the trash with nautilus] $ gnome-open http://www.commandlinefu.com [opens commandlinefu in your default webbrowser]

Get ssh server fingerprints
Get your server's fingerprints to give to users to verify when they ssh in. Publickey locations may vary by distro. Fingerprints should be provided out-of-band.

Save the list of all available commands in your box to a file
When you press TAB twice in your prompt, bash tells you something like "Display all 4567 possibilities? (y or n)" But when you press "y" you only get the list in the terminal output and, if you want to save it to a file, you have to copy it by hand from the vterm screen. With this utility you save the list to a file or pipe it to another command at will You can use the file saved list to grep for a particular pattern, useful if you are searching for a command but you only remember a few letters


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