Overview

Teaching: 0 min
Exercises: 20 min

Questions

Objectives

Assignment

The following are instructions. Go to the course website’s Week 1 assignment page for the list of questions to be answered and submitted.

1. For this course, you need to be using a Unix shell like Bash or ZSH. If you are on Linux or macOS, you don’t have to do anything special. If you are on Windows, you need to make sure you are not running cmd.exe or PowerShell; you can use Windows Subsystem for Linux or a Linux virtual machine to use Unix-style command-line tools. To make sure you’re running an appropriate shell, you can try the command echo $SHELL. If it says something like /bin/bash or /usr/bin/zsh, that means you’re running the right program.

2. Create a new directory called spring2021 under /tmp.

3. Look up the touch program. Remember that the man program is your friend.

4. Use touch to create a new file called datascibasics in spring2021.

5. Write the following into that file, one line at a time. The first line might be tricky to get working. It’s helpful to know that # starts a comment in Bash, and ! has a special meaning even within double-quoted (") strings. Bash treats single-quoted strings (') differently: they will do the trick in this case. See the Bash quoting manual page for more information.

    #!/bin/sh
    curl --head --silent https://wcm-datascibasics.github.io
   

6. Try to execute the file, i.e. type the path to the script (./datascibasics) into your shell and press enter. Understand why it doesn’t work by consulting the output of ls (hint: look at the permission bits of the file).

7. Run the command by explicitly starting the sh interpreter, and giving it the file datascibasics as the first argument, i.e. sh datascibasics. Why does this work, while ./datascibasics didn’t?

8. Look up the chmod program (e.g. use man chmod). This online interactive chmod calculator is a handy tool to have book marked in your browser.

9. Use chmod to make it possible to run the command ./datascibasics rather than having to type sh datascibasics. How does your shell know that the file is supposed to be interpreted using sh? See this page on the shebang line for more information.

10. Use | and > to write the “last modified” date output by datascibasics into a file called last-modified.txt in your home directory.

Key Points

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