sesion 3 admin linux

8/14/2019 Sesion 3 Admin Linux

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Editing Files


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Objectives

After completing this unit, you should be able to:Determine the type of file using file

Edit text files with vi

Discuss other text file editors such as kedit

Discuss the ways non-text files can be edited


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Editing Files

Use file command to determine the content of a file

To edit text files, use an editor

Non-text files can only be changed using the applicationthat created them, or with a "hex editor"

But most configuration files under Linux are text files!

$ file /etc/passwd

/etc/passwd: ASCII text

$ file /usr/bin/passwd

/usr/bin/passwd: ELF 32-bit LSB executable


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The "vi" text editor

Default editor in all UNIX operating systemsUsually the only editor available in emergencies

Relatively hard to learn, but really powerful

As a Linux user, you should be able to use vi for basicediting tasks

But it's OK if you prefer another editor for daily work

vi in Linux is usually vim (vi improved):Syntax highlightingArrow keys, Del, BS work in insert modeMulti level undoMouse support


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vi Modes

vi knows three modes of operationCommand mode (for simple, one-letter commands)Edit mode (insert text)ex mode (for complicated commands)

Can easily change between modes

Command mode Edit mode

ex mode

Allows you to type simple,

one-letter commandsAllows you to insert text

Allows you to execute

complex commands


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Starting vi

~

~

~

~~

~

~

~~

~

~

~~

~

~

"myfile.txt" [New File] 0,0-1 All

$ vi myfile.txt


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Editing Text in Command Mode

To delete a single character under cursor xTo delete a single character left of cursor X

To replace a single character r

Undo the last change u

To repeat last command .

To join two lines together J

command mode


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Switching to Edit Mode

To insert text at begin of line ITo insert text before cursor i

To append text after cursor a

To append text at end of line A

To go back to command mode

Command mode Edit mode

IiAa

ESC


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Adding Text in Edit Mode

This file contains some lines.

Line 2.

And this is line 3.

Line 4 follows line 3.The last line is line 5.

~

~

~~

~

-- INSERT -- 3,8 All

Keystroke "i" switches vi to edit mode. New characters

can be inserted at the current position of the cursor

E iti th Edit M d


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Exiting the Edit Mode


Line 2.

And this for example is line 3.


~

~

~~

~

~

3,8 All

Keystroke "ESC" leaves the edit mode.

S hi f P tt


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Searching for Patterns

To search for a pattern (in command mode): /To repeat the previous search: n


Line 2.

And that for example is line 3.

Line 4 follows line 3.

The last line is line 5.

~

~

~

~

~

~

/line

R l i P tt


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Replacing Patterns

Advanced search and replace can be done in exmode:To replace old with new: :1,$s /old/new/g


Line 2.



~

~

~~

~

~

: 1,$s/this/that/g

C t C d P t


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To cut a whole line into buffer: ddTo copy a whole line into buffer: yy

To cut a word from the current cursor

position to its end: dw

To paste contents of buffers here: p

To cut, copy multiple lines, proceed command bynumber: 3dd, 8yy

Cut, Copy and Paste

Cut and Paste


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Cut and Paste


Line 2.




Line 2.

Line 4 follows line 3.

The last line is line 5.And that for example is line 3.

cut line 3 by pressing "dd"

...and insert it afterline 4 by pressing "p"

Copy and Paste


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Copy and Paste


Line 2.




Line 2.

And that for example is line 3



copy line 3 by pressing "yy"

...and insert it afterline 5 by pressing "p"

vi Options


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vi Options

Options entered in ex mode change the behavior of the vieditor::set all:set autoindent/noautoindent

:set number/nonumber:set list/nolist:set showmode/noshowmode

:set tabstop=x:set ignorecase/noignorecase:set wrapmargin=x:set tx/notx

:set hlsearch/nohlsearch:syntax on/off

To make this options available to all vi sessions,put it into a .exrc or.vimrc file in your HOME-directory

Exiting vi


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Exiting vi

To save and exit in command mode ZZTo save in ex mode :w

To forcefully save file in ex mode :w!

To quit without saving in ex mode :q

To forcefully exit in ex mode :q!

To save and exit in ex mode (recommended) :wq

To save and exit in ex mode, shorter :x

vi Cheat Sheet


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vi Cheat SheetEdit mode

Ex mode

kh

j

l

cursor move

save&exit

ZZex mode

:

or

search, repeat

/ nundo, redo

u .

Command mode

I i a A To edit mode

cut, copy, paste line

dd yy p

join lines

J

$

G

1G

^

search and replace

:%s /old/new/g

change settings

:set ...save, exit

:w :w!:q :q!

Can now type

text. Note: in

vim arrow keys,Del, Backspace

will work!delete char, word

x X dw

:wq:x

Other Editors


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Other Editors

A typical Linux distribution comes with a large number ofeditors. Examples:

Text mode editors

pico (really simple)Originalviemacs (even more powerful and complicated than vi)

Graphical mode editorskedit, kwritegedit

Hex editors allow you to change non-text files if you knowthe internal structurekhexedit

Unit Summary


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Unit Summary

The most common editor on any UNIX is vivi has three modes of operation: command mode, editmode and ex mode

vi makes a copy of the file you are editing in an editbuffer. The contents are not changed until you save thechanges

A typical Linux distribution comes with a lot of othereditors as well


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Linux Utilities

Objectives


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Objectives

After completing this unit, you should be able to:

Use the find and locate command to search for files

Use the cut command to list specific columns of a file

Use the grep command to search text files for patternsUse the head and tail commands to view specific lines ina file

Use the sort command to sort the contents of a file

Use the type,which and whereis commands to findcommands

Use the file command to find out the content of a file

Use thejoin and paste commands to combine files

Manipulate files with gzip,gunzip and zcat

The find Command


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The find Command

Search one or more directory structures for files thatmeet certain specified criteria

Display the names of matching files or execute

commands against those files

Syntax:

$ find path expression

Sample Directory Structure


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Sample Directory Structure

/

home

joe

sizeshapecolor

blue

brown

green

big

giant

little

small

box

circle

phone

square

blues

phonephone1

phone2

Using find


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Using find

Generally, you want to search a directory structure forfiles with certain names and list the names found.

$ cd /home/joe

$ find . -name phone./shape/phone

./phone

On many other UNIX systems, with find you have to tellit specifically to print the names using -print

$ find . -name phone -print./shape/phone

./phone


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Interactive Command Execution


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The -ok option also causes command execution but onan interactive basis:

$ find . -name b\* -ok rm {} \;< rm ... ./color/blue > ? y

< rm ... ./color/brown > ? y

< rm ... ./shape/box > ? y

< rm ... ./size/big > ? y< rm ... ./blues > ? y

Additional find Options


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p

-type fd

ordinary filedirectory

-size +n-nnc

larger than n blockssmaller than n blocksequal to n characters

-mtime +x-x

x

modified more than x days agomodified less than x days ago

modified x days ago-perm onum

modeaccess permissions match onumaccess permissions match mode

-user user finds files owned by user-newer ref.file file was modified more recently

than ref.file-o-a Logical ORLogical AND

find Examples


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p

$ find . -perm 777

./size/little

File matches expr 1 and expr 2:$ find . -name 's*' -type f -a -size +2\

>-exec ls -i {} \;

187791 ./shape/square

202086 ./size/small

File matches expr 1 or expr 2:

$ find . -name big -o -name 'c*'

./color

./shape/circle

./size/big

locate Command


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locate allows you to quickly find a file on the system,based on simple criteria

Requires that the superuser runs updatedb regularly

Most distributions run updatedb automaticallySuSE does not install locate/updatedb by default

$ locate passwd

/usr/share/man/man1/passwd.1.gz/usr/share/man/man5/passwd.5.gz

/etc/passwd

/usr/bin/passwd


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cut Example (1)


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$ cat /etc/passwd

root:x:0:0:Big Brother:/root:/bin/bash

shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

tux1:x:500:500::/home/tux1:/bin/bashtux2:x:501:501::/home/tux2:/bin/bash

$ cut -f1,6,7 -d: /etc/passwd

root:/root:/bin/bashshutdown:/sbin:/sbin/shutdown

tux1:/home/tux1:/bin/bash

tux2:/home/tux2:/bin/bash

cut Example (2)


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$ ps

PID TTY STAT TIME COMMAND

374 p0 S 0:00 -bash460 p0 R 0:00 ps

$ ps | cut -c-5,20-

PID COMMAND374 -bash

471 ps

The grep Command


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Searches one or more files or standard input for linesmatching pattern

Simple match or Regular Expression

Syntax

grep [options] pattern [file1 ...]

grep Sample Data Files


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Phone 1:

Phone 2:

Allet 10300 intern

Judith 20500 intern

Kees 30500 externLeo 40599 extern

Nannie 50599 extern

Peter 60300 intern

Allet 1342 intern

Judith 2083 internKees 3139 extern

Leo 4200 intern

Nannie 5200 intern

Peter 6342 extern

Basic grep


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$ grep 20 phone1Judith 20500 intern

$ grep 20 phone*

phone1:Judith 20500 intern

phone2:Judith 2083 intern

phone2:Leo 4200 intern

phone2:Nannie 5200 intern

$ grep -v Judith phone2

Allet 1342 intern

Kees 3139 extern

Leo 4200 internNannie 5200 intern

Peter 6342 extern

grep with Regular Expressions


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Patterns with metacharacters should be in single quotes(' ') so that the shell will leave it alone

Valid metacharacters with grep: $ . * ^ [ - ]. Any single character* Zero or more occurrences of the

preceding character[a-f] Any ONE of the characters in the

range a through f^a Any line that starts with a

z$ Any line that ends with z

grep Options


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-v Print lines that do not match

-c Print only a count of matching lines

-l Print only the names of the files with

matching lines

-n Number the matching lines

-i Ignore the case of letters when makingcomparisons

-w Do a whole word search

-f Read expressions from file instead of

command line

Other greps


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fgrep allows only fixed strings (no regular expressions)

egrep allows for multiple (alternate) patterns

What does the following command do?

$ egrep '20500|40599|50599' phone1

Judith 20500 intern

Leo 40599 extern

Nannie 50599 extern

$ grep 30 phone1 | grep intern

????????

The sort Command


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The sort command sorts the lines in the file specified andwrites the result to standard output

sort -t(delimiter) +field -options file

$ cat animals

dog.2

cat.4penguin.10

$ sort animals

cat.4dog.2

penguin.10

sort Examples


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$ sort +0.1 animals

cat.4

penguin.10

dog.2

$ sort -t. +1 animals

penguin.10

dog.2

cat.4

$ sort -t. -n +1 animals

dog.2

cat.4

penguin.10

Options:

-d sorts in dictionary order. Only letters, digits and spaces are

considered in comparisons

-r reverses the order of the specified sort-n sorts numeric fields in arithmetic value

The head and tail Commands


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The head command can be used to view the first fewlines of a file or files. The command syntax is:$ head [-lines] file(s)

The tailcommand displays the last few lines of a file or

files. The command syntax is:$ tail [{-lines|+lines|-f}] file(s)

$ head -5 myfile

$ ls -l | head -12

$ tail -20 file

$ tail +20 file

$ tail -f file

The type, which and whereis Commands


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To find out what the path to a command is, use type

To find out where the binary is located, use which

To locate the binary, source and manual page files of a

command, use whereis

$ type find echo

find is /usr/bin/find

echo is a shell builtin

$ whereis find echo

find: /usr/bin/find /usr/man/man1/find.1

echo: /bin/echo /usr/man/man1/echo.1

$ which find echo

/usr/bin/find

/bin/echo

The file Command


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With the file command, you can find out what the type ofdata in the file is.

$ file /etc/passwd /bin/ls /home/peter /tmp/fake.jpg/etc/passwd: ASCII text

/bin/ls: ELF 32-bit LSB executable, Intel 80386,version 1, dynamically linked, stripped

/home/peter: directory/tmp/fake.jpg: PDF document, version 1.3

The gzip, gunzip and zcat Commands


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$ ls -l file1

-rw-rw-r-- 1 team01 team01 32031 Apr 6 23:40 file1

$ gzip -v file1file1: 89.9% -- replaced with file1.gz

$ ls -l file1.gz

-rw-rw-r-- 1 team01 team01 3265 Apr 6 23:40 file1.gz

$ zcat file1

(output is the same as the output of the cat command with

the uncompressed file)

$ gunzip file1

$ ls -l file1

-rw-rw-r-- 1 team01 team01 32031 Apr 6 23:40 file1

To compress or uncompress files use gzip, gunzip orzcat

The join and paste Commands


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$ cat one

a apple another

b bee beast

$ cat two

a ape

b broken

$ join one two

a apple another ape

b bee beast broken

$ paste one two

a apple another a ape

b bee beast b broken

join and paste combine files

Unit Summary


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The following commands were considered:

The find command is used to recursively searchdirectories for files with particular characteristics

The grep command is used to select entire linescontaining a particular pattern

The head and tail commands are used to view specific

lines in a fileThe sort command sorts the contents of a file by theoptions specified

Find out where you can find commands with type, whereand whereis

The gzip, zcat and gunzip commands can be used to

create and work with compressed files

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