Sunday, October 28, 2012

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@

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", \

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}]




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