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SEEM3460 Tutorial

Unix Introduction

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Introduction What is Unix?

An operation system (OS), similar to Windows, MacOS X

Why learn Unix? Greatest Software Ever Written!!

http://www.informationweek.com/shared/printableArticle.jhtml?articleID=191901844

Freely available clone/distributions are under rapid development (e.g. Linux & FreeBSD)

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Using Unix Shell: a program that acts as a middleman

between you and the UNIX OS Terms similar to shell:

Terminal / virtual terminal Console

A shell allows users to Run programs Manage I/O of processes easily

A Unix shell interprets a programming language (sometimes called the shell script)

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A shell command ls -lp ~

ls: program name “ls” is the utility to list files

-lp: options/switches, starting with a hyphen “l” means list in long format “p” means putting a slash after directory names

~: remaining parameters actual meaning depends on the program used for ls, the remaining parameters are the files or

directories to be listed “~” means the home directory of the current user

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Utilities

Unix utilities are the basic programs supporting the user to control the system

Examples: date: shows the system date man -s 1 ls: shows help on ls from the

built-in manual section 1 pwd: prints the working directory echo: prints a message

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Unix file system in brief A hierarchy of directories To locate a file in the system, a pathname is needed

Command: pwd print your current working directory

Pathnames Absolute pathnames

Starting from the root (with a beginning “/”) Relative pathnames

Starting from the current working directory

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Managing Files on Unix (1)

Creating an empty file touch <newFileName>

Creating (making) a directory mkdir <newDirName>

Moving (renaming) a file mv <aFileName> <aDirectoryName> mv <oldFileName> <newFileName>

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Managing Files on Unix (2) Change working directory

cd <aDirName> List files in a directory or fits the pattern

ls <directories/filename patterns> View the content of a file

cat <file paths> more <file paths> less <file paths> head <file path> tail <file path>

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Managing Files on Unix (3)

Copying a file cp <oldFileName> <newFileName>

Remove a file rm <aFileName>

Remove a non-empty directory rm –r <aDirName>

Remove a whole directory without prompt rm –rf <aDirName>

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Editing a file nano

Adv: simple, easy to learn and use Dis: no GUI

emacs Adv: has GUI, easy for beginners Dis: relatively slow

vi/vim (vim stands for Vi Improved) Adv: fast for advance users Dis: text-version is quite difficult to learn GUI version: gvim, rgvim To learn, type “vitutor” in console

Check their “man” page for detail usages

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Compiling C programs in Unix Compiler:

cc – the native C compiler under Unix gcc – C compiler under GNU project Usage is the same, gcc is more popular

To compile a C source code file, say example.c, type in: cc example.c gcc example.c The output of both compilers (i.e. the executable) would be “a.out” by

default To override the default executable name, use “-o” flag

cc example.c –o example gcc example.c –o example You can name the executable as .exe or .bin file to remind yourself the

nature of the file One more tip, use “-Wall” to get some warning messages

Warning message usually indicate hidden bugs Try to understand the error messages and warning messages. For other flags, “man cc” or “man gcc”

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Compiling C programs in Unix If there are so many compilation errors that it

cannot fit into one screen. One way is to compile by the following command:

cc example.c |& more It means that the compilation errors will be

displayed screen by screen. That is, it will display the first screen of errors and

wait. After the user examines the errors, he/she can

choose to display the next screen of errors by hitting RETURN or quit by hitting Control-C. Then, the user can go back to modify the source code.