1. Welcome to Linux A quick overview of some ideas and commands of most frequent use to programmers using Linux

2. Two interface options The ‘modern’ graphical desktop interface: –Objects are represented as colorful icons –Users operate mainly by clicking the mouse –It’s ‘intuitive’ (like Macintosh or Windows) The ‘legacy’ command-line interface: –Objects are accessed by their file-names –Users operate by typing in commands –It’s flexible and powerful, but demands knowledge!

3. Toggle between interfaces If your workstation is configured for the Graphical Desktop Interface by default (also known as ‘runlevel 5’), it is easy to switch to the Command-Line Interface by typing a keystroke-combination: -Fn (for n = 1, 2,..., 6) You can return to your Graphical Desktop by typing: -F7

4. All Linux’s objects are ‘files’ All ordinary files are sequences of ‘bytes’ Some store data, others store programs Also there are some ‘special’ files (such as ‘directories’, device-files, and pseudo-files) Each file has a unique name Each file has a specific ‘owner’ Each file has a set of ‘access permissions’

5. File ‘permissions’ rwxrwxwwx OwnerGroupAll Legend r = ‘read access’ (1 = yes, 0 = no) w = ‘write access’ (1 = yes, 0 = no) x = ‘execute access’ (1 = yes, 0 = no) Bitmap-example: 110-100-100 Octal representation: 0644 ASCII-representation: rw-r--r--

6. Directory Tree / /home /boot /etc/bin /usr /var For a current Linux installation (such as Fedora Core 5), the topmost directory (named ‘/’) will typically contain only about two-dozen sub-directories. Linux organizes its hundreds of thousands of files into a tree-like hierarchy.

7. Directory Tree / /home /boot /etc/bin /usr /var /cruse /brooks /parr /root … The ‘/home’ directory contains a sub-directory for each authorized user. superuser

8. Directory Tree / /home /boot /etc/bin /usr /var /grub /vmlinuz /System.map The ‘/boot’ directory contains the files and directories that are needed to select, load, decompress, and begin executing the Linux kernel … compressed kernel

9. Directory Tree / /home /boot /etc/bin /usr /var The ‘/etc’ directory stores files concerned with the system’s configuration-options. /inittab /fstab /hosts … /X11

10. Directory Tree / /home /boot /etc/bin /usr /var /mkdir/chown/kill The ‘/bin’ directory contains about a hundred of the most necessary and basic binary-executables (such as the programs which implement the minimal set of commands you need for system-recovery in the unlikely event of a ‘crash’ ). …

11. Directory Tree / /home /boot /etc/bin /usr /var /include/bin /src /lib /local The ‘/usr’ directory contains about a dozen sub-directories which organize the vast majority of the various kinds files needed for a useful work-environment. Together these sub-directories contain tens of thousands of files and programs. …

12. Directory Tree / /home /boot /etc/bin /usr /var /log/spool /lock … The ‘/var’ directory contains about two-dozen sub-directories that pertain to various value-added resourses (such as system log-files or users’ email).

13. Unique filenames To give each file a name that’s unique, the directory-tree hierarchy is utilized: / /home /cruse /hello /brooks /hello ‘/home/cruse/hello’‘/home/brooks/hello’

14. The online ‘manual’ Linux offers online documentation for all of its commands (and for its library functions) You type ‘man ’ to view the relevant page of this online manual Example: $ man ls# view ‘ls’ options Some commands have numerous options that are explained (but seldom illustrated)

15. Command-usage examples: ‘ls’ The ‘LiSt’ command: $ ls –$ ls# files in present working directory –$ ls /# files in the topmost (‘root’) directory –$ ls ~# files in YOUR home-directory –$ ls –l# files with their attributes –$ ls –a# files (‘all’ including the ‘hidden’ ones) –$ ls *.c# files having the ‘.c’ filename-suffix –$ ls *# files in every immediate sub-directory –$ ls..# files in the parent-directory –$ ls my*# files whose names begin with ‘my’

16. My own ‘top-30’ commands cd# Change Directory cp# CoPy file (or files) mv# MoVe file (or files) rm# ReMove file (or files) rename# RENAME a file (or files) who# who else is using station mkdir# MaKe a new DIRectory rmdir# ReMove DIRectory

17. My “top-30” (continued) scp# Secure CoPy ssh# Secure Shell lpr# Line-Printer cat# conCATenate file(s) grep# global reg-expr printer uname-r# shows kernel-release ln –s# creates a ‘soft’ link

18. My “top-30” (continued) vi# VIsually edit a text file gcc# Gnu C Compiler g++# Gnu C++ compiler as# Assembler ld# Linker make# compile-and-link script objdump -d# disassemble program

19. My “top-30” (continued) tar# uncompresses a file diff# compares two textfiles exit# terminates a user-session time# time a program’s execution chmod# change file’s access-mode su# Substitute User more# view textfile page-at-a-time

20. Recommend keeping a ‘journal’ Some notes I find useful for reference… –For extracting a new Linux kernel release $ tar –xvf linux-2.6.16.6.tar –For combining several files of a new project $ tar –cvf linux-2.6.16.6.tar *

21. Some practice exercises… Switch from your Graphical Desktop to a Text-Mode Console Interface (6 choices) Switch from one text-console to another Login to that console Type the ‘ls’ command Log out from that console Return to your Graphical Desktop

22. Some exploration exercises… Use ‘cat’ to look at one of the hidden files in your own ‘home’ directory, like this: $ cat.bash_history Use ‘ls’ to look at the names of all the files in your own ‘Desktop’ directory, like this: $ ls -a Desktop Use ‘cd’ to change your current directory to the ‘root’ directory, like this: $ cd /

23. An ‘advanced’ exercise Create a subdirectory named ‘bin’ in your own home directory, like this: $ cd ~# ‘~’ is your home-directory $ mkdir bin# creates ‘bin’ sub-directory Copy a program-file from a class-website, then compile it, move the executable into your ‘~/bin’ subdirectory, and finally execute it, like this: $ cp /home/web/cruse/cs630/dump.cpp. $ g++ dump.cpp -o dump $ mv dump bin $ dump dump.cpp