The Linux system does not have a default directory

[Problem description]
First in the Linux home directory did not find pictures this directory, so first create a pictures, but
When you use the shortcut key PRTSCRN or ALT+PRTSCRN or SHIFT+PRTSCRN, the picture is not generated in that directory.

[Solutions]
The key cause of the problem is that my system does not currently have a default desktop directory, such as documents, Music, Videos
You only need to install the Xdg-user-dirs
$ sudo apt-get install xdg-user-dirs
After the system restart, found that the default directory appears, shortcut keys can also be used.

The Linux system does not have a default directory