1. PWD shows the current folder you are working on.
2. Type cd / to go to the root dictionary.
3. Absolute route (cd /home/dq) vs. relative path (cd home).
4. Type whoami to check the current username.
5. Type cd ~ to go back to the user folder.( home directory)
6. Type mkdir test to create a test folder in the current directory.
7. -v is an opinion of a command, and the function is to show the detail of the command.
8. mkdir --help is to understand all the possible opinions of mkdir
9. ls is to show all the directory, ls -l is to show all the detailed directory.
10. We use rmdir to delete the dirtectory.
11. touch test.txt is to create a file named test.txt. touch command can also updata/modify files.
12.
原文：http://www.cnblogs.com/kingoscar/p/6009846.html