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Working With The Command Line

Linux 101

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Manual pageshttp://linuxmanpages.com

man man

man uses the less pager

Space one page forward

Esc + V one page backward

/ search

Q quit

Manual sections

1 Excutable programs

2 System calls

3 Library calls

4 Device files

5 File formats6 Games

7 Miscellaneous

8 System administration commands

9 Kernel routines

man passwdman 5 passwd

passwd command

section 1

/etc/passwd file

section 5

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Create / Modify

Locate

View

Copy

Move

Rename

Archive

Compress

Delete

Linux treats almost everything as a file

regular files, directories, devices, sockets, pipes

touch, vi, nano, mkdir

less, ls

cp, dd

mv

tar, cpio

gzip, gunzip,

bzip2

rm, rmdir find, locate

Basic file management

$ dd if=/dev/sda of=mbrsave bs=512 count=1

Create a backup copy of the MBR

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General notions

Linux is case sensitive

Filename.txt filename.txt Special filenames

. current directory

.. parent directoryFilenames can contain any character.

Filenames can be 255 characters long.

Wildcards

* zero or more characters

? only one character

[] character set

Wildcard expansion = file globbing

Filenames should never contain

wildcards: * ? \

quotations:

path separator: /

$ cd /usr/bin

$ pwd

$ cd .$ pwd

$ cd ..

$ pwd

filesystem dependent

$ touch fileone filetwo

$ touch file*

$ rm file*

A wildcard stands in place of a group of characters

Replacing an wildcard with chars to obtain

file names in the current directory

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Shell implementations

bash bsh tcsh csh ksh zsh

Bourne Again Shell

Bourne Shell

C Shell Korn Shell Z Shell

/bin/sh symbolic link to the default shell

Linux shell

Internal commands

echo

exec

time

exit

logout

cd

cd ~

change directory

pwd print working directory

clear clear screen

replaces the shell

set

env export

ls

most common

In linux

$ ls l /bin/sh

$ ls

l /bin/*sh

some can also be external commands

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Linux shell

Command Completion TAB

Command History

Ctrl + P

Ctrl + N

UpArrow

DownArrow

Ctrl + R reverse search

Ctrl + S forward search

Ctrl + G terminate search

History Search

~/.bash_history

history display all historyhistory c clear history

Bash configuration: /etc/profile ~/.bash_profile

Line editing

a command line in the shell

Ctrl+KDelCtrl+X; Bkspdelete

move Ctrl+ECtrl+Amove by one wordCtrl+Left Ctrl+Right

$ less ~/.bash_history

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read a variable

$ echo $HOSTNAME

$ env

displays all environment variables

set a variable$ export HOSTNAME=lpic.credis.ro

set local variableexport to the environment

$ HOSTNAME=lpic.credis.ro

$ export HOSTNAME

When retrieving the value of a variable precede

the variable name with a '$' character

Common environment variables:

USER/USERNAME - Username of current user

SHELL - Path to the current command shell

PWD - Present Working Directory HOSTNAME - TCP/IP name of the computer

HOME - Home directory of current user

PATH - List of directories where executables are found

PS1 - Default prompt in bash

DISPLAY - The display used by X (:0.0)

EDITOR - The default text editor

SHELLENV

CHILD

SHELL

ENV

launchcopy

$ env

Launch a shell with a

modified environment

Environment variablesmeans of passing named data

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Streams, pipes & redirection

programstdin stdout

stderr

Standard Input Standard Output

Standard Error

< >>

2> 2>>

&>

here-is document

Discard errors $ command 2> /dev/null

tee [options] [files] Writes input to stdout and files-a, --append

program1 | program2

pipe

send output of program1 to input of program2

append

$ cat Some simple text

!

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Exercises

1. An administrator runs a program and he wants to log the errors into the error.log file

but also display them in the shell. What command could he use?

2. Consider the following command:

$ touch data01 data02 data11 data12 data13

What are the commands (use different wildcards) for the following tasks:

Delete data01 and data02

Delete data11 and data13 Delete all data files

3. One installs some programs in the /opt/progs directory. What could be done such

that these programs can be executed without specifying the entire path? (Write a

command).

4. Write a command that you could use to create a backup of the systems configuration

files.