File Operations: Find and Print Files in Mathematica

It's easy to find files in Mathematica with FindFiles and wildcards. The only thing you have to remember is that the 2nd argument, which specifies the directories to search must be a List even if you only specify one directory.

What did I put in my init.m files to automatically load Packages? Let's find and print init.m. A directory intended for a user's init.m file $UserBaseDirectory<>Kernel.

folderToSearch=FileNameJoin@{$UserBaseDirectory,"Kernel"}
C:\Users\kwcarlso\AppData\Roaming\Mathematica\Kernel

The wildcard will retrieve all files in the directory.

filePath=FileNames["*",folderToSearch]
{C:\Users\kwcarlso\AppData\Roaming\Mathematica\Kernel\init.m}

We use FilePrint to print it. Use First@ or Sequence@@ to remove the unnecessary List brackets around the filepath.

FilePrint@First@filePath
(*
(** 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.\n"

Print@"Loading C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica\\Scribble.m\n"
<<"C:\\Users\\kwcarlso\\AppData\\Roaming\\Mathematica\\Scribble.m"

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

(* put this in Pre-Load Functions at some point? 
On[General::newsym] *)

Print@"Loading C:\\Program Files\\Wolfram Research\\Mathematica\\9.0\\AddOns\\ExtraPackages\\Utilities\\cleanSlate.m\n"
<<"C:\\Program Files\\Wolfram Research\\Mathematica\\9.0\\AddOns\\ExtraPackages\\Utilities\\cleanSlate.m"
*)

Suppose we wanted to search for all files of a given type in Mathematica's default List of filepaths, $Path, like "init.m". Important! Note that $Path includes the root directory "." and my user root directory "C:\Users\kwcarlso." We don't want to search those so we find their Positions in $Path (need to add a backslash to the path separators since a single backslash tells Mathematica to treat the following character specially and a double backslash is treated as a single backslash).

omitPaths=Position[$Path,#]&/@{".","C:\\Users\\kwcarlso"}
{{{8}},{{9}}}

Using Drop to lose the directories at the two Positions we found, we search the remaining ones but still get far too many files. You can evaluate this command in your Notebook if you wish.

tooManyFiles=FileNames["init.m",Drop[$Path,Flatten@omitPaths],Infinity];

So let's just specify the directories that we want with the inner List in Part.

desiredDirectories=$Path[[{2,3,5}]]
{C:\Users\kwcarlso\AppData\Roaming\Mathematica\Kernel,C:\Users\kwcarlso\AppData\Roaming\Mathematica\Autoload,C:\ProgramData\Mathematica\Kernel}

autoloadFileNames=FileNames["*",desiredDirectories]
{C:\ProgramData\Mathematica\Kernel\init.m,C:\Users\kwcarlso\AppData\Roaming\Mathematica\Autoload\PacletManager,C:\Users\kwcarlso\AppData\Roaming\Mathematica\Kernel\init.m}

To search all subdirectories in the directories, add a third argument, "Infinity", or an integer to limit the depth searched.

autoloadFileNames=FileNames["*",desiredDirectories,Infinity];

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.

File Operations: Deleting Files

Delete one or more files

DeleteFile deletes one file, or more files if they are given in a List. If you are deleting more than one file, typically you'd first use FileNames to acquire those files from a directory. DeleteFile returns Null (i.e. nothing) if it works and $Failed if it doesn't. To delete a few files in the current directory it's as simple as this.

FileNames["test*", "C:\\Users\\82V\\Documents"] // DeleteFile

Here is a more complicated example in which I delete 3500 files in multiple directories.


Acquire FileNames and Delete Files in all subdirectories

The usual sequence of steps goes like this. Set the directory in which you want to search for files. In Windows, I usually use Windows Explorer to navigate to the directory, then click in the address bar to select it, Ctrl+C to copy it, and paste it after a quote mark in Mathematica, which says to me:

In[114]:= SetDirectory@
  "C:\\Users\\82V\\Documents\\Neuroscience\\Arle-Shils\\commandUNCuS\\\
DataFiles";

Search for all the files using a wildcard and store their names in a variable (datFiles). Search in all subdirectories within your directory by using a wildcard for subdirectory names in the optional second argument, and Infinity for depth of subdirectories in the optional third argument.

In[97]:= datFiles = FileNames["*.dat", {"*"}, Infinity];

See how many filenames you captured.

In[98]:= datFiles // Length

Out[98]= 3594

Take a quick peek at the first five files to be deleted to make sure you're capturing the right ones.

In[99]:= datFiles[[1 ;; 5]]

Out[99]= {"Short_Test_File\\tc125_101.dat", "Short_Test_File\\tc125_101pre.dat", \
"Short_Test_File\\tc125_102.dat", "Short_Test_File\\tc125_102pre.dat", \
"Short_Test_File\\tc125_103.dat"}

Delete all the files to be deleted.

In[100]:= DeleteFile@datFiles

Reset the directory to whatever it was before you set it to the one in which to search for files.

In[112]:= Directory[]

Out[112]= "C:\\Users\\82V\\Documents\\Neuroscience\\Arle-Shils\\commandUNCuS\\DataFiles"

In[113]:= ResetDirectory[]

Out[113]= "C:\\Users\\82V\\Documents"

Note that if you set the directory n times to delete files in each, you need to repeat ResetDirectory[] that many times to get it back to where it was, since each time you set a directory it pushes the previous ones down a stack (which you can reveal using DirectoryStack[]), and each time you use ResetDirectory[] it pops the directories back up the stack. You can use a Do loop on ResetDirectory[] n times to do this. Using the Print statement will show you the pop sequence of directories you have visited. I prefaced the command with Directory[] to show the current directory first.

In[117]:= Directory[]; Do[Print@ResetDirectory[], {3}]

C:\Users\82V\Documents\commandUNCuS

C:\Users\82V\Documents\Neuroscience\Arle-Shils\commandUNCuS\DataFiles

C:\Users\82V\Documents