Look at the world through the shell

Echo is similar to the LS command. Many functions can be implemented through regular expressions.

For example, we can use echo. * To display all the files under the current folder, but by using echo-d. [!.]? * You can remove the current directory and the last directory.

Arithmetic extensions , arithmetic uses a format of $ ((expression)) in which arithmetic operators can be identified as subtraction and exponentiation.

Curly brace Extensions , which may be the strangest way to expand, can create multiple text strings through patterns inside curly braces. For example, echo {a.. Z} will display all English characters from A to Z. Again for example we want to print from 2010-01, 2010-02 ... 2015-12 what to do, try the echo {2010..2015}-0{1..9} {2010..2015}-1{10..12}, hurry up, if you want to create these folders at the same time, what to do, remember the previous Xargs command bar, If you don't remember, go ahead and turn it over.

command Substitution , you can use the output of a command as an extension mode. For example, file $ (ls/usr/local/bin/* | grep zip), meaning to display the details of all files containing a zip under the/usr/local/bin/folder.