Chapter 3 Study Guide

CNT-2311-Chapter 3

Exploring Linux Filesystems

Objectives

• Comparison of Windows and Linux filesystems
• Navigate the directory structure using relative and absolute pathnames
• Types of files
• View filenames and file types
• Use shell wildcards
• Display contents of files
• Search files for regular expressions using grep
• Use vi to modify text files
• Alternatives to vi
• File Hierarchy
• Comparison of Windows v. Linux filesystems�

 

Navigate the directory structure using relative and absolute pathnames 

start in home dir

 use ~ to reference home directories

present dir = pwd

/home/randy/

change dir = cd

cd /etc - change directory to /etc

relative path name = path to the file in relation to the current working directory

".." references the next higher up dir

tab-completion!

 

Types of files

Text, Binary, Executable

Directory = still just a file

Linked = reference other files, shortcut

Special device files = reference hard disks or ports, contained in /dev

Named pipes = communication between process in memory

Created using mkfifo or mknod One process is a reader other is a writer Sockets = named pipes between remote computers Filenames Filename facts 255 max characters alphanumeric, _ -  .   may or may not have extension to denote type Lots of different extensions 

Links

• http://learn.clemsonlinux.org/wiki/File_extensions 
• http://www.debianhelp.co.uk/fileext.htm 
• http://filext.com/alphalist.php?extstart=%5EL  (not limited to linux) 

Commands to view filenames and file types

pwd - Show current directory

pwd - /home/randy

ls -ltr   - Show listing and give color codes to information

listing including file permissions, ownership and date/time stamp.

Executable files: Green

Normal file : Normal

Directory: Blue

Symbolic link : Cyan

Pipe: Yellow

Socket: Magenta

Block device driver: Bold yellow foreground, with black background

Character device driver: Bold yellow foreground, with black background

Orphaned syminks : Blinking Bold white with red background

Missing links ( - and the files they point to) : Blinking Bold white with red background

Archives or compressed : Red (.tar, .gz, .zip, .rpm

Image files : Magenta (.jpg, gif, bmp, png, tif)

View filenames and file types

•  ls -F = gives file type, special character is listed on the left of the name = Metacharacters=

• @ = linked file

• = exe

• / = subdirectory

• = is a socket

• | = named pipe

Other files do not have special character appended to them - they can be anything not listed above

• ls -l = ls long listing

When listing files/directories a special character on the left indicates what type of file it is

• d = dir
• L = linked
• b & c = special device files
• n = named pipe
• s = socket
• - = other - txt, bin

Display contents of files   vi - editing a file   emas - alternative to vi   cat - concatenation - similar to "type" in DOS/Windows.   tac - reverse concatenation - types file in reverse   head - displays the top ten lines of a file   tail - displays the bottom ten lines of a file   more - displays file page by page   less - similar to more but allow line by line manipulation Key Terms ~ metacharacter absolute pathname binary data file command mode concantenation directory Emacs (Editor MACroS) editor executable program filename filename extension gedit editor home directory insert mode linked file log file   named pipe file nano editor parent directory regexp regular expressions relative pathname socket file special device file subdirectory Tab-completion feature text file text tools vi editor wildcard metacharacters    � � Key � �Commands� �    cat  cd (change directory) egrep fgrep file grep head less ls more pwd (print working directory) strings tac tail Search files for regular expressions using grep grep allows you to search through a file for text argument.   grep "localhost" /etc/hosts     return lines that include localhost in the file /etc/hosts

grep -v "localhost" /etc/hosts     return lines that DONT include localhost in the file /etc/hosts

grep -l "LOCALHOST" /etc/hosts     return lines that include localhost in the file /etc/hosts that is not case-sensitive       Regular Expressions Commands to Display Contents of Binary Files  strings = searching binary file for text  od = displays file in octal format  od -x = displays contents in hex

Searching for Text within Files Tools: grep, awk, sed, vi, emacs, ex, ed, C++, PERL, tcl Regular expressions Wildcard metacharacters are interpreted by the shell Regular expressions are interpreted by text tool program Wildcard metacharacters match characters in file & dir names Regular expressions match charters within file Wildcard metacharacters typically have different definitions than regular expressions metacharacters There are more regular expression metacharacters than wildcard metacharacters

Emacs
Not installed by default in Fedora 13.
Can run in a GUI environment.
More GUI than vi.

 Written in C and Emacs Lisp.  Licensed GNU GPL  Users can combine commands into macros

   to automate task.

Summary Linux file system is a hierarchy,  series of directories paths are absolute or relative Many types of files - text, scripts, executable, dirs, linked, special device ls - view file names and many options to modify view Wildcard metacharacters help to select multiple files Regular expression metacharacters are used in many ways. Text files can be viewed differently with commands such as, head, tail, cat, tac, more and less. vi is the most common text editor however GUI options exits  

References

• Anatomy of the Linux File System

http://www.ibm.com/developerworks/linux/library/l-linux-filesystem/

• File extensions

http://learn.clemsonlinux.org/wiki/File_extensions

http://www.debianhelp.co.uk/fileext.htm

• Linux/Unix/BSD Post-Exploitation Command List

https://docs.google.com/document/d/1ObQB6hmVvRPCgPTRZM5NMH034VDM-1N-EWPRz2770K4/edit?hl=en_US

• vi tutorial

http://www.unix-manuals.com/tutorials/vi/vi-in-10-1.html

• VI Cheatsheet

 http://www.atmos.albany.edu/deas/atmclasses/atm350/vi_cheat_sheet.pdf

• Learning the vi and Vim Editors

http://www.amazon.com/Learning-Vim-Editors-Arnold-Robbins/dp/059652983X/ref=sr_1_1?s=books&ie=UTF8&qid=1326846342&sr=1-1 

• Command Guides

http://wiki.ihcnt.net/w/Linux_command_guide

http://wiki.ihcnt.net/w/Linux-command-list 

• Emac Guide

http://sean.wenzel.net/docs/emacs/quick_reference/ 

• 15 Practical examples of ls commands

http://www.thegeekstuff.com/2009/07/linux-ls-command-examples/

• 50 Most Frequently Used UNIX / Linux Commands http://www.thegeekstuff.com/2010/11/50-linux-commands/