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Use a var with more text only if it exists
See "Parameter Expansion" in the bash manpage. They refer to this as "Use Alternate Value", but we're including the var in the at alternative.

Connect to FreeWifi hotspot (France) and keep the connection active
(In French) Connection aux hotspots FreeWifi, et maintien de la connection active

Fast portscanner via Parallel

Are the two lines anagrams?
This is just a slight alternative that wraps all of #7917 in a function that can be executed

Count the number of characters in a string from the standard input.

Tricky implementation of two-dimensional array in Bash.
Since Bash doesn't support two-dimensional arrays, you can limit your columns length by some big enough constant value ( in this example 100 ) and then index the array with i and j, or maybe write your own get() and set() methods to index the array properly like I implemented for example ( see Sample output ). For example for i=0 and j=0...99 you'll pick up one of 100 elements in the range [0,99] in the one-dimensional array. For i=1 and j=0...99 you'll pick up one of 100 elements in the range [100,199]. And so on. Be careful when using this, and remember that in fact you are always using one-dimensional array.

Uniformly correct filenames in a directory
Useful if non-ascii characters in filenames have been improperly encoded. Replace "PROBLEM" with the incorrect characters (e.g. 'é'), and "FIX" with the correct ones (e.g. '?').

Click on a GUI window and show its process ID and command used to run the process
This command is useful when you want to know what process is responsible for a certain GUI application and what command you need to issue to launch it in terminal.

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

recursive search and replace old with new string, inside files
If you can install rpl it's simpler to use and faster than combinations of find, grep and sed. See man rpl for various options. time on above operation: real 0m0.862s, user 0m0.548s, sys 0m0.180s using find + sed: real 0m3.546s, user 0m1.752s, sys 0m1.580s


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