Working with Files and Directories

SciencesPo Intro To Programming 2024

Florian Oswald and The Software Carpentry

29 April, 2024

Intro

Questions

  • How can I create, copy, and delete files and directories?
  • How can I edit files?

Objectives

  • Create a directory hierarchy that matches a given diagram.
  • Create files in that hierarchy using an editor or by copying and renaming existing files.
  • Delete, copy and move specified files and/or directories.

Creating Directories

  • Let’s create a directory thesis here:
$ cd ~/shell-lesson-data/exercise-data/writing
$ ls -F

this outputs:

haiku.txt  LittleWomen.txt
  • Use mkdir to create:
$ mkdir thesis

used like this, thesis is created in the current directory. While with the -p flag we created nested subdirectories:

$ mkdir -p ../project/data ../project/results

Good File Names

Bad File Names

  1. Don’t use spaces. Spaces don’t work well on unix file names. north pacific gyre is not a good one. Use north-pacific-gyre instead.
  2. Don’t begin with -.
  3. Stick with letters, numbers, ., -, and _

Creating a Text File

  • Let’s go into the thesis directory and create a text file called draft.txt.
$ cd thesis
$ nano draft.txt

TEXT Editor

nano is a super simple editor, and you can use it only to edit text files (That’s normal for text editors 😉). You will probably switch to a more powerful editor later on (I recommend VSCode), but nano is a good starting point. Notice that ^ key is the Ctrl key, so ^X means Ctrl + X.

Filename Extensions

Task

  1. Go to your home directory: cd
  2. create an empty file with the touch command:
$ # this is a comment, by the way 
$ cd  # so, going home.
$ touch new_doc.pdf  # creating an empty file.
  1. Open your file browser and double click on new_doc.pdf. What is going to happen?
  • Ok, let’s get rid of that file now.
  • use the rm command (more later)
$ rm new_doc.pdf
  • Caution: rm is forever gone.
  • You can add -i interactive to be safe(r).

Moving Files and Directories

  • Let’s go back to the writing directory
$ cd ~/shell-lesson-data/exercise-data/writing
  • Let’s rename draft.txt to quotes.txt with mv.
$ mv thesis/draft.txt thesis/quotes.txt
  • Now let’s actually move it into the current dir:
$ mv thesis/quotes.txt .
  • Notice: mv x y means x is gone afterwards!

Challenge

Jamie placed maltose.dat and sucrose.datfiles in the analyzed folder by mistake. He wants to move those back to the raw folder now:

$ ls -F  
 analyzed/ raw/
$ ls -F analyzed
fructose.dat glucose.dat maltose.dat sucrose.dat
$ cd analyzed

What has to go in the blanks to achieve this?

$ mv sucrose.dat maltose.dat ____/____
Show Solution

Solution

$ mv sucrose.dat maltose.dat ../raw

Copying Files and Directories

  • cp x y is similar to mv x y, but you keep x.
$ cp quotes.txt thesis/quotations.txt
$ ls quotes.txt thesis/quotations.txt
  • the -r option means recursively and copies entire folders:
$ cp -r thesis thesis_backup
$ ls thesis thesis_backup
  • Notice that rm -r mydir will delete everything inside the mydir folder!

Using Wildcards

  • the * character is a wildcard, i.e it matches all characters:
$ cd shell-lesson-data/exercise-data/
$ ls proteins/p*
proteins/pentane.pdb    proteins/propane.pdb

Reproducing a Folder Structure

Suppose we want to create the following structure on our computer:

2016-05-20/
└── data
   ├── processed
   └── raw

Challenge

Which sequence will achieve this result?

1.
$ mkdir 2016-05-20
$ mkdir 2016-05-20/data
$ mkdir 2016-05-20/data/processed
$ mkdir 2016-05-20/data/raw
2.
$ mkdir 2016-05-20/data/raw
$ mkdir 2016-05-20/data/processed
3.
$ mkdir -p 2016-05-20/data/raw
$ mkdir -p 2016-05-20/data/processed

Nice Trick

  • Oh by the way.
  • If you are on MacOS, try to this on the command line
$ open .
  • Pretty handy!

Tip

  • cp [old] [new] copies a file.
  • mkdir [path] creates a new directory.
  • mv [old] [new] moves (renames) a file or directory.
  • rm [path] removes (deletes) a file.
  • * matches zero or more characters in a filename, so *.txt matches all files ending in .txt.
  • ? matches any single character in a filename, so ?.txt matches a.txt but not any.txt.
  • Use of the Control key may be described in many ways, including Ctrl-X, Control-X, and ^X.
  • The shell does not have a trash bin: once something is deleted, it’s really gone.
  • Most files’ names are something.extension. The extension isn’t required, and doesn’t guarantee anything, but is normally used to indicate the type of data in the file.
  • Depending on the type of work you do, you may need a more powerful text editor than Nano.

SciencesPo Intro To Programming 2024