As a student of computing, you’re going to have to spend a lot of time using computers. Computers have great interfaces these days, but programmers still spend a surprising amount of time interacting with text-based interfaces to their machines.

In this lab, I’d like you to play around with the command line a bit. First, I’d like you to read the following guide. Read it up until (but not including) the section on “Looping Over a Set of Files.”

Lab Assignment

  • Open a web browser with an email addressed to me, titled <your name>'s Lab 1. Start filling out the questions as I ask you to do them.

  • Start inside your home directory (if you are not there, type cd ~, the perhaps-confusing name ~ is an alias to your home directory).

  • Create a directory lab1 via mkdir lab1

  • Navigate into that directory cd lab1

  • The command touch <filename> “touches” a file. Every file has a “timestamp” showing when it was create, modified, etc.. Touching a file updates this timestamp. If the file does not yet exist, `touch ` creates an empty file of the specified name.

  • Run touch hello.

  • Now run stat hello. This asks the computer to tell you some statistics about the file, including its size, when it was created, etc..

  • Copy and paste the output of the command in your email to me.

  • Google a little bit about how stat works. Figure out how to make it print the time the file was last modified.

  • Now run touch hello again, followed by stat hello. What changed? And why?

  • Open any editor on your computer and create a file named text.txt inside of the lab1 folder. Put a few lines of text in the file, really anything you want. This can be any editor: GEdit if you’re on linux, TextEdit if you’re on mac, or nano, emacs, or vim if you’re used to using one of those.

  • Now type cat text.txt, which shows the contents of the file.

  • Now type cat text.txt text.txt. cat accepts multiple arguments.

  • Now type cat >text.txt. Be prepared: the command won’t terminate. It will allow you to keep typing until you type the character to stop typing (Control-D on most machines) and kill the program, and will write that into the file.

  • Type a few lines, and then hit Control-D.

  • Now cat the file again.

  • Copy the file text.txt to the parent directory: cp text.txt .. (equivalently, you could have done cp text.txt ../text.txt).

  • Now–without changing the directory–use cat to print the file to the screen. Tell me what command you used to do that.

  • Now change the directory to the parent directory: cd ...

  • This should be your home directory. Print the working directory by using the pwd command (print working directory).

  • Now remove the folder and the file: rm -r -i lab1. Note that the -r option means “recursive” (i.e., delete directories, not just files), and the -i option means “interactive” (i.e., ask before deleting any files). If you want, you could have typed in rm -ri lab1. Often, when there are multiple flags you can pass to programs, you can pass multiple at once by simply putting them together (this is not always true, but it is for “core utilies” like rm).

  • Now also remove the copied text.txt by doing rm text.txt.

  • To complete your email to me, answer the following questions:
    • What scares you the most about using the command line?
    • Name the most interesting / useful thing you learned in this lab
    • Is there any situation in which you’d rather use the command line rather than a visual user-interface?
  • Send your email to me and I’ll put you down with a 100% within a week.