We know how create directories in the file system tree, change the location of the current directory within that tree, and create and edit text files. Now we will learn a few Unix commands to manage and maintain our text files.

The following unix commands can be used to remove (delete), copy, and move or rename a file.

The rm Command

The rm works much like the rmdir command, only it takes a file instead of a directory as an argument.

The cp Command

The cp command behaves differently depending on whether its second argument is a file or a directory. For example, given a directory, dir, with subdirectory, subdir and containing the text file, file.txt:

dir
├── file.txt
└── subdir

The command:

$ cp file.txt newfile.txt

run inside the dir directory will create a newfile.txt in the directory.

dir
├── file.txt
├── newfile.txt
└── subdir

while the command:

$ cp file.txt subdir

will create a copy of file.txt with the same name in the subdir directory.

dir
├── file.txt
└── subdir
    └── file.txt 

The mv Command

The mv command is used to change the location of a file or directory as well as to change the name of a file or directory without changing its location.

Assume the current working directory is named dir, and that it contains two subdirectories and a text file as follows:

dir
├── file.txt
├── subdir1
└── subdir2

Running:

$ mv file.txt renamed.txt 

from within the dir directory results in a new name for file.txt in the same location:

dir
├── renamed.txt
├── subdir1
└── subdir2

while:

$ mv renamed.txt subdir1

results in a new location for renamed.txt without changing its name:

dir
├── subdir1
│   └── renamed.txt
└── subdir2

In the exercises you will see how to change name and location at the same time.

Hacking Our File System Tree with a Machete: rm -rf

The approach we have taken so far to managing directories and files can be likened to leaves growing out of the ends of a branch (mkdir) and being pruned one at a time at the tip (rmdir and rm). Now we look at a way to hack off entire sections of our file system tree with a machete.

We have already seen an example of a command argument (also called a command flag, command option, or command switch) with the ls -l command. Starting with the following directory structure:

dir2
├── sub1
├── sub2
│   ├── subsub1
│   │   └── subsubsub1
│   │       └── file2.txt
│   └── subsub2
│       └── file1.txt
└── sub3

Running the following command from within the dir2 directory:

$ rm -rf sub2

results in:

dir2
├── sub1
└── sub3

Pruning the file system tree at sub2 and removing it and all the directories and files inside it and their decedents.

Exercises:

1. Assuming you have the word.txt file you created in the previous lesson, type the following at the unix command prompt:

     $ cp word.txt word2.txt

   Use the ls command to verify that you now have both word.txt and word2.txt. Use ls -l see that they are the same size. Edit word2.txt to see that it has the same content as word.txt. Now run:

     $ rm word.txt

   Again list the files in your current working directory with ls to confirm that word.txt has been deleted (removed).

   Finally, use the mv command to change the name of the file back to word.txt

2. The following image shows a directory tree related to foods and food groups.

   

   After being told to create this directory, your assistant tried, but made numerous mistakes. Download foods.tgz and run the following command at your bash prompt in the same directory with the file:

     $ tar xzvf foods.tgz
     

   This will create a directory tree that looks like this:

       foods/
       ├── cereals
       │   ├── beans.txt
       │   └── legumes.txt
       ├── cheetos.txt
       ├── dairy_and_eggs
       │   └── eggos.txt
       ├── fruits
       │   ├── fish_and_seafood.txt
       │   ├── fruits.txt
       │   ├── mil_prodcts.txt
       │   └── skittles.txt
       ├── grains.txt
       └── meats
           ├── poultry.txt
           ├── red_meats.txt
           └── vegetables
               ├── alliums.txt
               ├── cruciferous_veggies.txt
               ├── green_veggies.txt
               ├── mushrooms.txt
               └── roots.txt
     

   Your job is to fix all the mistakes your assistant made and put the foods directory into the form shown in the screenshot.