Lecture 18 - Linux and C

Goals

• Learn some basic Linux commands

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Working on Linux

we are going to be doing our work on basin, which is one the department’s Linux servers While you can acquire the tools that we will be using for your machine, we are going to rely on a consistent toolchain for everyone (and force you to learn a little Linux along the way)

To start, we need an SSH client to connect to basin. If you are running MacOS or Linux, it is built in. If you are running WSL (Windows Subsystem for Linux), you also have one. Otherwise you will need to find one.

The built in ones are command line interface (CLI) tools – they only run on the command line, so you need to open up a terminal (or something similar).

When you open a terminal, you are running a program called a shell. The shell has a number of different responsibilities – this is the important subset for what we are doing.

• it keeps track of your PATH (the directories containing executable programs)
• it provides mechanisms for traversing a directory structure
• manages programs that are launched from the shell
• it has some basic programmable functionality

ssh to basin from a shell

ssh username@basin.cs.middlebury.edu

Note that you need to be on the campus network to be able to do this.

You should now be using a second shell – one that is running on the remote machine

Navigation

Three important commands for navigation (these are provided by the shell)

• cd [path] - “change directory”
• ls [path] - list the contents of the current directory
• pwd - print working directory

The file system is a treelike data structure made up of a hierarchy of directories

Directory names are separated by the slash character (/)

When we navigate we can use relative or absolute paths

An absolute path gives the entire directory structure from the root and always starts with a /

A relative path is specified relative to your current working directory

• it could be just the name of a file or directory in the directory you are working in (cs202)
• it could be multiple directories deep (cs202/s23)

There are some special symbols for specifying path elements

• ./ refers to the current directory (this is primarily important for running programs)
• ../ refers to the parent directory – we can use this to climb up out of our current directory
• ~/ refers to your home directory

Other tools

• ssh - secure shell: allows us to run programs on remote machines securely (by default, we are running a remote shell)
• man - the manual tool, which will have much information about command line tools. The format is a bit dense, so scan it to look for examples and descriptions of the available flags
• vim - a command line text editor
• emacs - another command line editor

Mechanical level

vocabulary

Skills