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Manual sections

1 Excutable programs2 System calls3 Library calls4 Device files5 File formats6 Games7 Miscellaneous8 System administration commands9 Kernel routines

man passwd

man 5 passwd

passwd commandsection 1

/etc/passwd filesection 5

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

General notions

Linux is case sensitive

Filename.txt filename.txt Special filenames. current directory.. parent directory

Filenames 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 obtainfile names in the current directory

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

exitlogout

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

Linux shell

Command Completion TAB

Command History

Ctrl + P

Ctrl + N

UpArrow

DownArrow

Ctrl + R reverse searchCtrl + S forward searchCtrl + 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 word

Ctrl+Left Ctrl+Right

$ less ~/.bash_history

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

Streams, pipes & redirection

program stdin 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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