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Watch Network Service Activity in Real-time

pretend to be busy in office to enjoy a cup of coffee
Not as taxing on the CPU.

Create a tar archive using 7z compression
Using 7z to create archives is OK, but when you use tar, you preserve all file-specific information such as ownership, perms, etc. If that's important to you, this is a better way to do it.

Display the top 10 running processes - sorted by memory usage
A pretty nice display of processes.

Determine if photos have been rotated to portrait orientation instead of normal landscape orientation
Most people take photos in landscape orientation (wider than it is tall). Sometimes though you turn the camera sideways to capture a narrow/tall subject. Assuming you then manually rotate those picture files 90 degrees for proper viewing on screen or photo frame, you now have a mix of orientations in your photos directory. This command will print out the names of all the photos in the current directory whose vertical resolution is larger than its horizontal resolution (i.e. portrait orientation). You can then take that list of files and deal with them however you need to, like re-rotating back to landscape for consistent printing with all the others. This command requires the "identify" command from the ImageMagick command-line image manipulation suite. Sample output from identify: $ identify PICT2821.JPG PICT2821.JPG JPEG 1536x2048 1536x2048+0+0 8-bit DirectClass 688KB 0.016u 0:00.006

Count items in JSON array
Pipe any JSON to jq, then count with the appropiate expression and use the | length on the array

Extract neatly a rar compressed file
It's also possible to delay the extraction (echo "unrar e ... fi" |at now+20 minutes) wich is really convenient!

find out how many days since given date
You can also do this for seconds, minutes, hours, etc... Can't use dates before the epoch, though.

List the binaries installed by a Debian package
GNU grep's perl-compatible regular expression(PCRE).

Check to make sure the whois nameservers match the nameserver records from the nameservers themselves
Change the $domain variable to whichever domain you wish to query. Works with the majority of whois info; for some that won't, you may have to compromise: domain=google.com; for a in $(whois $domain | grep "Domain servers in listed order:" --after 3 | grep -v "Domain servers in listed order:"); do echo ">>> Nameservers for $domain from $a


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