Load Functions at Startup Using Initialization Files

See also Example of a File of Functions to Pre-Load at Startup.

When you quit the kernel, Mathematica forgets everything that has happened in a session, such as variable assignments and function definitions. But you can use init.m files to automatically load anything from simple functions, to arbitrarily complex programs, or even external program calls that you want it to know or do on startup. When you accumulate functions that you want to always be available, you can save them in a text file or Package and load them on startup.

There are init.m files in a number of locations—the two intended for user use are in your $UserBaseDirectory /Kernel and /FrontEnd folders. Kernel/init.m will run when you start the Kernel while FrontEnd/init.m will run when you first open a Notebook during a Mathematica session. I recommend using the Kernal init.m since the Front End init.m typically has a lot of stuff in it and since you may Quit the Kernel during a session and want to re-load what's in your init.m file when you re-start it.

First, locate your user init.m files. "Environment variables", which are parameters set for your local environment, i.e. your computer and user account, are one category of $commands. $UserBaseDirectory is for your personal use.

In[1]:= $UserBaseDirectory

Out[1]= "C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica"

We can search for any init.m file in this Directory. Note the inclusion of Infinity or the search would leave out sub-directories.

In[2]:= initFiles = FileNames["init.m", $UserBaseDirectory, Infinity]

Out[2]= {"C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica\\FrontEnd\\init.m", \
"C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica\\Kernel\\init.m"}

Let's take a quick look at the contents of the Kernel init.m using FilePrint, which displays the contents of a text file like a text editor without executing any functions. Here is my init.m files after I modified it. You can see it will Print a Message saying hello and telling me its location, then load some functions that I want available in any Session.

In[3]:= FilePrint@Last@initFiles

(** User Mathematica initialization file **)

Print@"Hello World from your kernel init.m file! I'm located in:\n
C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica\\Kernel."

<<"C:\\Users\\kwcarlso\\Dropbox\\Mathematica\\Initialization\\Pre-Load Functions.txt"(** User Mathematica initialization file **)

Print@"Hello World from your kernel init.m file! I'm located in:\n
C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica\\Kernel."

<<"C:\\Users\\kwcarlso\\Dropbox\\Mathematica\\Initialization\\Pre-Load Functions.txt"

To set this up similarly for yourself:

1. Locate your Kernel/init.m file as shown above.
2. Copy and paste its filepath into your file manager (e.g. Windows Explorer) or otherwise navigate there.
3. Open the init.m file with a text editor (e.g. Notepad).
4. Add the Print statement with your init.m location.
5. Add the filepath to your pre-load functions file.

The easiest way to prepare functions for automatic re-use is to save them in a text file. Two other methods are using Initialization Cells or Packages. Functions stored in a text file or a Package are loaded with Get (<<), which does execute them as it reads them in. Initialization Cells (menu: Cell/Cell Properties/Initialization Cell or /Initialization Group) are the most common method used by beginners.

Saving functions in a text file is a good intermediate step for beginners who aren't ready to create Packages. Just take care to start your function names with small letters so you don't accidentally use the name of a built-in function, and Clear your definitions before defining them.

Clear@functionName; functionName[parameter1_,parameter2_,...]:=definition

Appendix: Locations of All Users' init.m Files

You can execute this cell and see where the initialization directories for all users are located:

In[4]:= {$BaseDirectory,$UserBaseDirectory}//TableForm

Out[4]
C:\ProgramData\Mathematica
C:\Users\kwcarlso\AppData\Roaming\Mathematica

There are four possible init.m files to modify, depending on whether you want to initialize on Kernel or Front End startup, and for all users or just the user who is logged in.