Command line 1: Mac version

General

• References: Much of the content of these sessions is summarized at our Command line quick reference page.
• Credit: Our materials are based on the Software Carpentry Unix Shell course
• Etherpad: We’ll create an Etherpad where participants who wish to do so can take notes collaboratively. For a quick overview of Etherpad functionality see http://write.flossmanuals.net/etherpad/introduction/.
• Something to play with: Follow the instructions at http://swcarpentry.github.io/shell-novice/setup.html/ to copy some practice files.

Why and how do we use the shell?

• The shell is a program that runs other programs.
• We use the shell to interact with the computer on the command line (CLI ~ GUI).
• The Unix philosophy is that you can pipe (chain) together small commands, each of which does one thing well, to do something complex. You can’t do this in a GUI.
• bash = ‘Bourne again shell’ (the original Bourne shell is sh; others include csh, ksh, tcsh, zsh).
• Learn the shell on a need-to-know basis.

Launching the shell

• For Mac OS X: the Terminal.app that you will find in the Applications → Utilities folder. (Many Mac users prefer the free third-party https://www.iterm2.com/.)
• For Windows: Although cmd.exe is the traditional Windows shell, and you may even have used it previously, we recommend bash. When you download Git, you’ll also download Git bash, the command line interface we use and recommend. (We do not recommend the Windows 10 “Ubuntu in Windows”.)
• For Ubuntu Desktop (Unity): you can hit Ctrl-Alt-T or you can type Terminal into the Search box.

Looking around

Change to your home directory, look at it with pwd.

• cd ~
• cd ..
• cd -
• cd; cd Desktop
• cd data-shell/data/s... (tab completion)
• cd /Users/djb/Desktop/data-shell/data (absolute path)

Change to Desktop/data-shell

• ls -F
• ls -j (unsuppored)
• man ls
• ls data

Dragging a file from your filesystem Finder/Explorer window to the terminal

ls switches

• ls -a: include hidden files (filenames starting with .)
• ls -l: show enhanced file information, including date and time stamps, owner and group, permissions
• ls -t: list in timestamp order
• ls -G: colored output
• ls -lh: human readable file size
• ls -F: decorate filenames according to filetype
• ls -d: don’t recurse into directories
• ls -1: single-column
• ls -d */: list only directories

History and completion

• Command and filename completion with the Tab key
• Command history with the arrow keys

Summary

• The file system is responsible for managing information on the disk.
• Information is stored in files, which are stored in directories (folders).
• Directories can also store other directories, which forms a directory tree.
• cd path changes the current working directory.
• ls path prints a listing of a specific file or directory; ls on its own lists the current working directory.
• pwd prints the user’s current working directory.
• whoami shows the user’s current identity.
• / on its own is the root directory of the whole file system.
• A relative path specifies a location starting from the current location.
• An absolute path specifies a location from the root of the file system.
• Directory names in a path are separated with ‘/’ on Unix (including Mac OS)
• .. means ‘the parent directory = the directory above the current one’
• . on its own means ‘the current directory’. Why would we need this?
• Most filenames have conventional extensions: .txt, .xml, etc.
• Most commands take options (flags) which begin with a -.