Linuxppt3

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Directory

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Used to organize other files into a logical tree structure

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Absolute pathname

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The pathname from the root directory up to a certain specified file or directory

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Root

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The top of the tree structure (different usage of word than the user root)

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Windows filesystem structure vs linux filesystem structure

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Windows is organized by drive letters which limits you to only save things on whatever drives are accessible. Linux starts off at root and everything is available from 1 to 2 directories down.

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Home directory

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Unique to each user

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pwd

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Print working directory command - it displays the current directory/working directory in the directory tree

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cd

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Change directory command - changes the current directory in the directory tree

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Relative pathname

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pathname of file or directory relative to the current directory

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Subdirectory

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Directory residing within another directory

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Tab-completion

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Pressing the tab key fills in remaining characters of a unique filename or directory name (??). Is a BASH shell feature.

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Text files

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Plain text characters, that is, standard keyboard characters

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Binary files

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Non-plain text files containing:
BINARY DATA FILES - data files with special fomatting e.g graphic files, and...
BINARY PROGRAM FILES - executable version of a program, that is, in machine language

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Directory files

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Used to organize files

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Linked files

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a file that points to another file

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Special device files

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Represent system devices

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Named pipes

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Identify channels that pass information between processes

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Socket files

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Allows a process on another computer to write to a local file

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Filename

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Identifier given to a file

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Filename extensions

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Identifiers following a dot (.) at the end of the filename. It denotes file type, although most linux files dont have extensions

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types of filenames 1

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.c - C programming language source code files, .cc or .cpp - C++ programming language source code files, .html or .htm - hypertext markup language files, .ps - files formatted for printing with post script, .txt - text files, .tar - archived files like zip on windows, .gz or .bz2 or .Z - compressed files, .tar.gz or .tgz, or .tar.bz2 or .tar.Z - compressed archived files, .conf or .cfg - configuration files, .so - shared object (prog. language) files, .o - compiled object files

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types of filenames 2

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.pl - PERL programs, .tcl - Tcl (Tool command language) programs, .jpg or .jpeg or .png or .tiff or .xpm or .gif - binary files that contain graphical images, .sh - shell scripts (contains text that is executed by the Shell)

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ls

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lists the files in a directory. May pass argument indicating directory to be listed.

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ls -f

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ls argument to list file types (file types shown in color as wel)

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ls -l

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argument to display a long file listing

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ll

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is the alias for ls -l.

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file

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command that displays the file type of any file

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Hidden files

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Files not normally displayed to the user. Start in command with a dot when naming file. These are often the configuration files of the computer that are hidden.

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ls -a

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Displays all files including hidden files

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ls -A or ls --almost-all

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lists most filenames (excluding the . and .. special files)

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ls -C

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lists filenames in column format

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ls --color=n

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lists filenames w/o color

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ls -d or ls --directory

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lists directory nanes instead of their contents

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ls -f

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lists all filenames w/o sorting

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ls -F or ls --classify

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lists filenames classified byn file type

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ls --full-time

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lists filenames in long format and displays the full modification time

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ls -l

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lists filenames in long format

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ls -lh or ls -l or ls --human-readable

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lists filenames in long format with human readable (easy-to-read) file sizes

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ls -1G or ls =1 or ls --no-group or ls -o

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lists filenames in long format but omits the group info

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ls -r or ls -reverse

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lists filenames reversely sorted

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ls -R or ls --recursive

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lists filenames in the specified directory and all subdirectories

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ls -s

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lists filenames and their associated size in kb

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ls -S

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lists filenames sorted by filesize

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ls -t

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lists filenames sorted by modification time

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ls -U

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lists filenames without sorting

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ls -x

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lists filenames in rows rather than in columns

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Wildcard Metacharacter

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Used to simplify commands specifying multiple filenames. Can be used with most linux filesystem commands.

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Wildcard Metacharacter Examples:

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* = matches 0 or more characters in a filename... ? = matches 1 character in a filename... [aegh] = matches 1 char in a filename - provided this char. is either an a,e,g or h... [a-e] - matches 1 char in a filename provided this char is either an a,b,c,d or e. [!a-e] matches 1 char in a filename provided this char is NOT an a,b,c,d or e.

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Concatenation

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Joining text together

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cat

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Command that displays (concatenates) contents of a text file to the screen. With option: -n that displays the line number and contents.

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Log files

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Contains records of past system events. The newest events are appended to the end.

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tac

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A command that displays text files in reverse order

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head

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Command to view first few lines of a file / preview. ALSO: Can specify what line # to start at... ex: head -5 filenamehere

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tail

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Command to view the last few lines of a file / preview. ALSO: Can specify what line # to start at... ex: tail -5 file1

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more

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Command that displays text files screen by screen. Space key goes to next page, Enter key goes to next line. Can be used with output of other commands.

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less

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Same as the 'More' comanbd, but can also use the cursor as well as PgUp and PgDwn to scroll. Can be used with output of other commands.

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"|" metacharacter

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Use if output is too large to fit on terminal screen.. is the pipe metacharacter, which uses the output of the previous command as the input for the following command (??)

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strings

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Command that searches for and displays text characters in a binary file. Will sometimes indicate the purpose of a binary file.

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To display correctly the contents of binary files..

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you'll typically want to use the program that originally created the file

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od

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Command that displays the contents of a file in octal format.

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Octal Format

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Numeric base 8 format for file display

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od -x

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Changes display from Octal to Hexadecimal format

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Hexadecimal Format

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Numeric base 16 format for file display

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Text Tools

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A tool to search for and manipulate text

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Regular expressions (regexp)

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Text wildcards that assist a search for specific text. It matches with text patterns.

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Regular expressions vs Wildcard metacharacters

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Metacharacters interpreted by the Shell; reg. expressions are interpreted by text tools. Metacharacters match characters in filenames - reg. expressions match chars within text files. There are more reg. exp. than wildcard metachar.

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Reg. Expressions Ex:

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* = matches 0 or more occurrences of the previous character, ? = matches 0 or 1 occurences of the previous character, + = matches 1 or more occurences of the previous character, . = matches 1 char. of any type, [...] = matches one char. from the numeric range specified within the braces, [^...] = matches one char. NOT from the range specified within the braces.

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Reg. Expressions Ex 2:

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{} = matches a specific number or range of the previous character, ^ = matches the following characters if they are the first characters on the line, $ = matches the previous characters if they are the last chars on the line, (. . . | . . . ) = matches either of two sets of chars.

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grep

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A command that displays lines in a text file matching a given regular expression... Requires 2 arguments: search string and files to search... which would be displayed as:

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grep -v

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Reverses meaning of previous command

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grep -i

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Case insensitive search

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Vim

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One of the oldest and most popular text editors for UNIX OS's... standard on most linux distributions... arvantage is portability (not usability)

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Bi-modal Editor in Vim

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Two possible modes for the program... Command Mode: performing text editing tasks not related to inserting text, and Insert Mode: inserting text, but nothing else

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vi

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Command to open Vim. Use vi filename to open file, or just vi to launch without opening a file right away.

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the vi editor

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i = changes to insert mode and places the cursor before the current character for entering text, a = changes to insert mode and places the cursor after the current character for entering text, o = changes to insert mode and opens a new line underneath the current line for entering text, l = changes to insert mode and places the cursor at the beginning of the current linie for entering text, A = changes to insert mode and places the cursor at the end of the current line for entering text, O = changes to insert mode and opens a new line above the current line for entering text, Esc = changes back to command mode while in insert mode.

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More Vim editor commands

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Look on table 4-6 for moving the cursor

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vi: w,, W, e, E

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Moves cursor forward one word

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vi: b, B

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Moves cursor back one word

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vi: 53G

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Moves cursor to line 53

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vi:G

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Moves cursor to last line in doc

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vi:0,

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Moves cursor to beginning of the line

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vi:$

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Moves cursor to end of line

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vi:x

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Deletes the character the cursor is on

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vi:3x

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Deletes three chars starting from the char the cursor is on

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vi:dw

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Deletes one word starting from the char the cursor is on

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vi:d3w,3dw

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Deletes 3 words starting from the char the cursor is on

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vi:dd

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Deletes one whole line starting from the line the cursor is on

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vi:d3d,3dd

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Deletes three whole lines starting from the line the cursor is on

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vi:d$

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Deletes from the cursor char to the end of the current line

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vi:d, d0

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Deletes from the cursor character to the beginning of the current line

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vi:yw

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Copies one word (starting from the char the cursor is on) into a temp buffer in memory for later use

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vi:y3w,3yw

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Copies three words (starting from the char the cursor is on) into a temp buffer in memory for later use

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vi:yy

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Copies the current line into a temporary buffer in memory for later use

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vi:y3y,3yy

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Copies 3 lines (starting from the current line) into a temporary buffer in memory for later use

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vi:y$

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Copies the current line from the cursor to the end of the line into a temporary buffer in memory for later use

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vi:y,y0

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Copies the current line from the cursor to the beginning of the line into a temporary buffer in memory for later use

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vi:p

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Pastes the contents of the temp memory buffer underneath the current line

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vi:P

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Pastes the contents of the temporary memory buffer above the current line

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vi:J

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Joins the line underneath the current line to the current line

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vi:[Ctrl]-g

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Display current line statistics

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vi:u

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Undoes the last function (undo)

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vi:'.' (period)

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Repeats the last function. (repeat)

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vi:/pattern

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Searches for the first occurrence of pattern in the forward direction

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vi:?pattern

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Searches for the first occurrence of pattern in the reverse direction

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vi:n

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Repeats the previous search in the forward direction

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vi:N

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Repeats the previous search in the reverse direction

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vi:':q'

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Quits from the vi editor if no changes were made

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vi:':q!'

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Quits from the vi editor and does not save any changes

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vi:':wq'

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Saves any changes to the file and quits from the vi editor

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vi:':w filename'

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Saves the current document to a file called filename.

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vi:':!date'

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Reads the output of the DATE command into the document under the current line.

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vi:':r filename'

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Reads the contents of the text file called filename into the document under the current line

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vi:':set all'

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Displays all vi environment settings

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vi:':set'

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Sets a vi environment setting to a certain value

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vi:':s/the/THE/g'

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Searches for the regular expression 'the' and replaces each occurrence globally throughout the current line with the word "THE"

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vi:':1,$ s/the/THE/g'

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Searches for the regular expression 'the' and replaces each occurrence globally from line 1 to the end of the doc with the word "THE"

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nano

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An easy to use common linux text editor with on screen command definitions

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Graphical Text Editors

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gedit editor: distributed with GNOME environment and kwrite editor: distributed with the KDE environment