UNIX and Linux

In this class we will interact with UNIX and Linux primarily through the command line. The command line, or shell, is very simple: it prompts you to type a command, then prints the output of the command (if any), then goes back to the prompt (like the shampoo).

At first, navigating the file system through the command line will be confusing. The two most important commands if you feel lost are ls and pwd. In UNIX there are no C: or A:, there is only one filesystem. The very top-level directory is /. Physical disks are mounted at certain locations in the filesystem tree. For our needs, we won't worry about this. We will work out of our home directories, aka ~ or $HOME. You will create subdirectories for your projects, e.g. ~/lab0/, then edit and compile your programs there.

Linux Quick Reference

Here are the most important UNIX commands. You should be able to do everything using these commands, but feel free to explore other commands. Most commands will print out a brief help screen with the -h or --help options. All commands have more in-depth man pages which you can read by typing man followed by the command name.

File/Directory Basics

ls list files
pwd print current working directory
cp copy files
mv move files
rm remove files
ln link files
cd change directory
mkdir create directory
rmdir remove directory

File Viewing

cat view files
less page through files
head view the beginning
tail view the end
nl number lines
od view binary data
xxd view binary data

Editors

File Properties

stat display file attributes
wc count bytes/words/lines
du measure disk usage
file identify file types
chmod change file permissions

Compiler

cc or gcc

Project

Now work through project 0.

C Tutorial

This is an excerpt of the major points of chapter 1 of "The C Programming Language" (K&R). The chapter and these notes are an overview, we won't go into all the details of these things here.

C programs consist of functions and variables.

Hello world:

#include <stdio.h>

main()
{
    printf("hello, world\n");
}

#include <stdio.h> means include the standard input/output header. A header is a file that tells the compiler what functions are available.
main is a function. The special name main is a special function: the one that runs when you run your program.
printf is a function from the stdio library (which is why we did #include <stdio.h>), it prints to the console.
"hello, world\n" is a string. \n means print a newline

As in algebra, variables are placeholders for values. In C variables have a type, e.g. int or float. (In-class excercise, write the fahrenheit-celsius table program.)

Introduce if and while

Introduce stdin and stdout, getchar() and putchar()

Write the line counting program in class. Discuss printf("%d\n",nl)

Overview arrays and functions