Several common misunderstandings in Linux

This article is from:Http://blog.csdn.net/hongchangfirst

1./USR and usr are not the abbreviation of user, But UNIX software resource. That is to say,/usr is the directory of UNIX operating system software resources.

In 2tar-jxvf filename.tar.bz2, F indicates filename, so it must be placed next to filename. The order of other attributes can be changed at will.

3. Wildcards and regular expressions are two different concepts. A wildcard is something in shell. A regular expression is a form of expression. For example, a wildcard * represents any character, including zero characters. A regular expression represents a quantitative relationship, the number of occurrences of the character at the front of a is zero or multiple times. For example, AA * indicates that a string appears at least once (in the unit of action ).