There are many Linux commands that are available on Android devices when you are using the terminal emulator app.
Firstly the ls command. This is used to list files in a directory.
Then the cat command; this is used to view the contents of a text file.
The mv command will move a file from one folder to another; or from one filename to another.
If you want to list the last commands executed in the terminal emulator app; the hash command will perform this task.
There is a nice Linux command list in this app; this is a good reference for the Linux user: https://play.google.com/store/apps/details?id=com.application.LinuxCommandList&feature=search_result#?t=W251bGwsMSwxLDEsImNvbS5hcHBsaWNhdGlvbi5MaW51eENvbW1hbmRMaXN0Il0..
Here is another good Android application with a lovely command reference for the Red Hat or Centos user: https://play.google.com/store/apps/details?id=com.northgatecomputing.redhat_centos_5_cheatsheet&feature=also_installed#?t=W251bGwsMSwxLDEwNCwiY29tLm5vcnRoZ2F0ZWNvbXB1dGluZy5yZWRoYXRfY2VudG9zXzVfY2hlYXRzaGVldCJd.
This app is a good one to have if you have a computer running Ubuntu. This is an Ubuntu One app that will automatically upload files from your `phone or tablet to the cloud: Ubuntu One app.
If you want to read UNIX/Linux manual pages whilst you are on the move; this app will be the perfect solution. Linux/UNIX man pages.
Finally; this is another good app for learning the Linux commands that are useful when you are getting to grips with your Linux installation.
Here is a video about the upcoming Ubuntu for ARM based Android mobile devices. This will be very interesting when this is finished; running a desktop Linux distribution on a mobile phone will be a reality.