Commands by john75 (0)

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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"

Quick plotting of a function
The arguments of "seq" indicate the starting value, step size, and the end value of the x-range. "awk" outputs (x, f(x)) pairs and pipes them to "graph", which is part of the "plotutils" package.

get you public ip address

Unlock more space form your hard drive
This command changes the reserved space for privileged process on '/dev/sda' to 1 per cent.

Selecting a random file/folder of a folder
Also looks in subfolders

When was your OS installed?
Show time and date when you installed your OS.

Change the From: address on the fly for email sent from the command-line
It's very common to have cron jobs that send emails as their output, but the From: address is whatever account the cron job is running under, which is often not the address you want replies to go to. Here's a way to change the From: address right on the command line. What's happening here is that the "--" separates the options to the mail client from options for the sendmail backend. So the -f and -F get passed through to sendmail and interpreted there. This works on even on a system where postfix is the active mailer - looks like postfix supports the same options. I think it's possible to customize the From: address using mutt as a command line mailer also, but most servers don't have mutt preinstalled.

Dump audio from video without re-encoding.
This removes the video and subsequent file size and directly copies the audio.

Simulate slow network connection locally
Replace 500ms by the desired delay. To remove it: sudo tc qdisc del dev lo root netem delay 500ms

Grab a list of MP3s out of Firefox's cache
Ever gone to a site that has an MP3 embedded into a pesky flash player, but no download link? Well, this one-liner will yank the names of those tunes straight out of FF's cache in a nice, easy to read list. What you do with them after that is *ahem* no concern of mine. ;)


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