Linux+ Guide to Linux Certification, Second Edition Chapter 4 Exploring Linux Filesystems

Linux+ Guide to Linux Certification, 2e Objectives Understand and navigate the Linux directory structure using relative and absolute pathnames Describe the various types of Linux files View filenames and file types Use shell wildcards to specify multiple filenames Linux+ Guide to Linux Certification, 2e

Objectives (continued) Display the contents of text files and binary files Search text files for regular expressions using grep Identify common text editors used today Use the vi editor to manipulate text files Linux+ Guide to Linux Certification, 2e

The Linux Directory Structure Directory: Used to organize other files into a logical tree structure Absolute pathname: Pathname from the root directory to a certain file or directory Root: The top level directory referred to using the / character Linux+ Guide to Linux Certification, 2e

The Linux Directory Structure (continued) Figure 4-1: The Windows filesystem structure Figure 4-2: The Linux filesystem structure Linux+ Guide to Linux Certification, 2e

Linux+ Guide to Linux Certification, 2e Changing Directories Home directory: Unique to each user pwd (print working directory) command: Displays current directory in the directory tree cd (change directory) command: Change the current directory in the directory tree ~ metacharacter: Refers to home directory Relative pathname: Pathname of file or directory relative to current directory Linux+ Guide to Linux Certification, 2e

Changing Directories (continued) Subdirectory: Directory residing within another directory Tab-completion: Pressing the Tab key fills in remaining characters of a unique filename or directory name BASH shell feature Linux+ Guide to Linux Certification, 2e

Viewing Files and Directories: File Types Text files: Store information in a readable text format Binary data files: Store information associated with executable programs Executable program files Directory files Linux+ Guide to Linux Certification, 2e

Viewing Files and Directories: File Types (continued) Linked files: Associated with another file Special device files: Represent system devices Named pipes: Identify channel that passes information between processes Socket files: Allow a process on another computer to write to a local file Linux+ Guide to Linux Certification, 2e

Linux+ Guide to Linux Certification, 2e Filenames Filename: Identifier given to a file Filename extensions: Identifiers following a dot (.) at end of filename Denote file type Most files on Linux do not have file extensions Linux+ Guide to Linux Certification, 2e

Filenames (continued) Table 4-1: Common filename extensions Linux+ Guide to Linux Certification, 2e

Filenames (continued) Table 4-1 (continued): Common filename extensions Linux+ Guide to Linux Certification, 2e

Linux+ Guide to Linux Certification, 2e Listing Files ls command: List the files in a directory May pass an argument indicating the directory to be listed –F switch: Argument to list file types –l switch: Argument to list long file listings Alias: Shortcut for a command ll command: Alias for ls -l File command: Displays file type of any file Linux+ Guide to Linux Certification, 2e

Listing Files (continued) Hidden files: Files not normally displayed to user Filenames start with a dot (.) Configuration files often hidden ls –a command: Displays hidden files Linux+ Guide to Linux Certification, 2e

Listing Files (continued) Table 4-2: Common options to the ls command Linux+ Guide to Linux Certification, 2e

Listing Files (continued) Table 4-2 (continued): Common options to the ls command Linux+ Guide to Linux Certification, 2e

Wildcard Metacharacters Wildcard metacharacter: Used to simplify commands specifying multiple filenames Can be used with most Linux filesystem commands Linux+ Guide to Linux Certification, 2e

Wildcard Metacharacters (continued) Table 4-3: Wildcard metacharacters Linux+ Guide to Linux Certification, 2e

Displaying Content of Text Files Concatenation: Joining text together cat command: Displays (concatenates) contents of a text file to the screen -n switch: Displays line number and contents Log files: Contain records of past system events New events appended to end tac command: Displays files in reverse order head command: View first few lines of a file Linux+ Guide to Linux Certification, 2e

Displaying Content of Text Files (continued) tail command: View last few lines of a file Can also specify what line number to start at more command: Displays text files page-by-page Space key goes to next page Enter key goes to next line less command: Same as more command, but can also use cursor to scroll Linux+ Guide to Linux Certification, 2e

Displaying Content of Text Files (continued) more and less can be used with output of other commands If output is too large to fit on terminal screen, use “|” metacharacter e.g., ls -l | more Linux+ Guide to Linux Certification, 2e

Displaying the Contents of Binary Files Typically use program that created the file strings command: Searches for and displays text characters in a binary file Might indicate purpose of binary file od command: Displays contents of file in octal format (numeric base 8 format) Linux+ Guide to Linux Certification, 2e

Searching for Text Within Files Text tools: Search for and manipulate text Regular expressions (regexp): Text wildcards that assist search for specific text Match patterns of text Used by many text tools and programming languages Including grep, emacs, C++, PERL, and many more Linux+ Guide to Linux Certification, 2e

Linux+ Guide to Linux Certification, 2e Regular Expressions Different from wildcard metacharacters Wildcard metacharacters interpreted by shell; regexps interpreted by text tools Wildcard metacharacters match characters in filenames; regexps match characters within text files More regexps than wildcard metacharacters Common and extended regexps Linux+ Guide to Linux Certification, 2e

Regular Expressions (continued) Table 4-4: Regular expressions Linux+ Guide to Linux Certification, 2e

Regular Expressions (continued) Table 4-4 (continued): Regular expressions Linux+ Guide to Linux Certification, 2e

Linux+ Guide to Linux Certification, 2e The grep Command grep (global regular expression print) command: Displays lines in a text file matching a given regexp egrep command: Displays lines of text that match extended regexps fgrep command: Does not interpret any regular expressions Returns results much faster than egrep grep requires two arguments Text to search for and files to search Linux+ Guide to Linux Certification, 2e

Editing Text Files: The vi Editor One of the oldest and most popular text editors for UNIX OSs Vim: Linux equivalent of vi Standard on most Linux distributions Advantage is portability, not usability Used on Unix and Linux Bi-modal editor (two possible modes): Command mode: Performs text editing tasks not related to inserting text Insert mode: Inserts text, but nothing else User environment is customizable Linux+ Guide to Linux Certification, 2e

Editing Text Files: The vi Editor (continued) Table 4-5: Common keyboard keys used to change to and from insert mode Linux+ Guide to Linux Certification, 2e

Editing Text Files: The vi Editor (continued) Table 4-6: Key combinations commonly used in command mode Linux+ Guide to Linux Certification, 2e

Editing Text Files: The vi Editor (continued) Table 4-6 (continued): Key combinations commonly used in command mode Linux+ Guide to Linux Certification, 2e

Editing Text Files: The vi Editor (continued) Table 4-6 (continued): Key combinations commonly used in command mode Linux+ Guide to Linux Certification, 2e

Editing Text Files: The vi Editor (continued) Table 4-7: Key combinations commonly used at the command mode : prompt Linux+ Guide to Linux Certification, 2e

Other Common Text Editors Mcedit editor (Midnight Commander Editor): Easy-to-use text editor Supports regexp Supports use of mouse for highlighting text Emacs (Editor MACroS) editor: Comparable functionality to vi Ctrl key combinations to perform special functions Supports LISP (LISt Processing) artificial intelligence programming language Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Table 4-8: Keyboard functions commonly used in the GNU emacs editor Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Emacs editor is not easy to use Must memorize key combinations Xemacs editor: Version of Emacs for KDE or GNOME GUI environments Easier to use than emacs Not available with every distribution Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Figure 4-3: The xemacs text editor Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Graphical text editors available with most Linux distributions: nedit editor gedit editor: Distributed with GNOME environment kedit editor: Distributed with KDE environment gedit and kedit offer more functionality than nedit Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Figure 4-4: The nedit text editor Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Figure 4-5: The gedit text editor Linux+ Guide to Linux Certification, 2e

Other Common Text Editors (continued) Figure 4-6: The kedit text editor Linux+ Guide to Linux Certification, 2e