UNIX Fundamentals 2010

7/31/2019 UNIX Fundamentals 2010

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UNIX Fundamentals

CTO/SDE

2009-5


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All Rights Reserved Alcatel-Lucent Shanghai Bell 20092 | Corporate Overview | January 2000

Agenda

UNIX Overview

UNIX File System

Process Control

Introduction to vi

Customizing Your Shell Environment

Other Basic Commands


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UNIX Overview


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What Is UNIX?

The UNIX Operating System (OS) is a large program (mostly coded in C) that turns

the computer into a useable machine.

UNIX is a multi-user, multi-tasking operating system.

UNIX is a machine independent operating system.

UNIX is a software development environment.


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A Brief History of UNIX

UNICS(1969)

Fourth Edition(1973)

Sixth Edition(1975)

Seventh Edition

(1979)

SYSV(1983)

BSD(1979)

Solaris/SunOs 5.x(SUN)AIX(IBM)IRIX(SGI)

HP-UN(HP)Digital UNIX(DEC)SCO Unix(SCO)UnixWare(SCO)

SunOs 4.x(SUN)ULTRIX(DEC)

NextStep(NeXT)

FreeBSD (Open Source)NetBSD (OPen Source)

OpenBSD (Open Source)

SVR4(1993)

*Linux (Open Source) (1991)


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Why Use UNIX?

multi-tasking / multi-user

Distributed processing

rich set of tools

powerful networking capabilities

stabile

portable (Hardware independence )

free! (FreeBSD, GNU)

profitable

1996 Sales: US$34.5 Billion, up 12%

active community


7/75All Rights Reserved Alcatel-Lucent Shanghai Bell 20097 | Corporate Overview | January 2000

Architecture of UNIX

Kernel

includes device driver

implements most BSD and SYSV system calls

Shells and GUIs

command line shell

GUIs: KDE, GNOME

Utilities & Application

Utilities : ls, cp, grep, awk, sed, bc, wc, more

Application programs: emacs editor, gcc

compiler



Login to UNIX systems

login: ad Enter your ID and RETURN.

Password: Enter your password and RETURN. It does not appear.

$ The UNIX prompt (or similar). You can now enter commands.

If you login with a graphical terminal, you can look for menus or icons whichmention the words "shell", "xterm", "console" or "terminal to open a shellprompt.



Logout from your account

logout

or

^D Press CONTROL and D together

Or

exit


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Change your password

The command is

$ passwd

It will ask you for the new password twice.

Password Tips

NEVER tell anyone your password.Dont write it down. A good password is:

- 8 (or more) characters long

- uses a mix of uppercase andlowercase letters, numbers, and symbols(e.g. #, %).


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General Command Syntax

The general syntax for a UNIX command is

$ command [-options] targets

Example:

ls -l /home/jones/dir1

Note: UNIX commands, options, and arguments are all Case sensitive!


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UNIX Help

man cmd Manual pages

Spacebar to go on; ^C to stopman ls

man man

whatis cmd One-line description

which cmd Location of command locate keyword List files with keyword in their name (or path)


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UNIX File System


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File types

The UNIX file system contains several different types of files

Regular file

Directory

Device

Link Socket

Named Pipe


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A simplified UNIX Directory Structure

. . .

. . . . . . .

. . .

. . .

/

etc bin dev tmp

date calhome

. . . . . .

will joan

play work proj1hobby.c. . .. . .


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Some Typical UNIX directories

/ The "root" directory

/bin Essential low-level system utilities

/usr/bin Higher-level system utilities and application programs

/sbin Superuser system utilities (for performing system administration

tasks)

/lib Program libraries (collections of system calls that can be included

in programs by a compiler) for low-level system utilities

/usr/lib Program libraries for higher-level user programs

/tmp Temporary file storage space (can be used by any user)

/etc UNIX system configuration and information files


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Some Typical UNIX directories (cont.)

/home User home directories containing personal file space for each user.

or /homes Each directory is named after the login of the user.

/dev Hardware devices

/proc A pseudo-filesystem which is used as an interface to the kernel.

Includes a sub-directory for each active program (or process).


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The home directory

When you log into UNIX, your current working directory is your user home

directory.

You can refer to your home directory at any time as "~" and the home directory

of other users as "~".

Willspecify the directory proj1?/

home

joan

proj1hobby.c. . .

will

play work

Will shome dir

. . .. . .

/ home /joan /proj1

~joan/proj1

~/play


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Pathnames

Absolute Pathnames

The sequence of directory names between the top of the tree (the root) and the

directory of interest.

Relative Pathnames

The sequence of directory names below the directory where you are now to the

directory of interest.

examples:

Absolute Pathnames Relative Pathnames Comments

/bin bin if you are in //etc/terminfo terminfo if you are in etc

/export/user/home/ad ../user/home/ad if you are in /export/tma

. the current directory

.. the parent directory


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File Permissions

There are three types of permissions supported by UNIX:

r (4) read, view the contents of a file or a directory

w(2) write, edit file/directory contents

x (1) execute, run executable file

There are three levels of permissions:

User (owner) the person who owns the file.

Group the group owns the file.

Other the rest of the world


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File Permissions

Heres an example

Suppose you type in ls -l and the result is

-rwxr-xr-- 1 hansdoc 858 Aug 22 22:28hw1

owner

group

size Modificationdate/time

Grouppermissions

OtherPermissions

links

type

Userpermissions

File name


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File Permissions

read=>4; write=>2; execute=>1

111

4 + 2 + 1

7 5 4

101

4 + 0 + 1

100

4 + 0 + 0

rwx r-x r--


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Changing Permissions

chmod [options]modefilename change file permissions with numerical mode

example:

chmod 641 hw1

6 4 1

110 100 001

rw- r-- --x

the owner of hw1 has rw-(6) permission, the grouphas r--(4) permission, others have --xpermission.


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Changing Permissions

chmod [options] who ops permissionfilename change file permissions with

symbolic mode

options

R recursively change permissions

who can be any combination of:u (user) g (group)

o (other/world) a (all or ugo)

ops adds or takes away permission, and can be:

+ (add permission) (remove permission)

permission can be any combination of:

r (read) w (write) x (execute)


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Changing Permissions (cont.)

examples:

chmod u+w test report add write permission on the files test and report for

their owners

chmod u-x abc.c take away execute permission on abc.c from owner

chmod g+rwx myfile1 add read, write and execute permissions on myfile1for the group

chmod ugo+rwx myfile2 add read,write and execute permissions on myfile2

for everyone


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Permission Mask

umask [-S] [mode] User file-creation mode mask

Option:

-S Produce symbolic output

Example: user group other

file default permissions: rw- rw- rw-

directory default permissions: rwx rwx rwx

$ umask u=rwx,g=rwx,o= (or $ umask 007)

$ mkdir foo

$ touch bar

$ ls -l

drwxrwx--- 2 user test 512 May 1 20:59 foo

-rw-rw---- 1 user test 0 May 1 20:59 bar


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Changing owner and group

chown user file change file ownership to another user

Must have the write permission on the file!

chgrp group file change file group to another user

Only owner or supervisor can change the group!

examples:chown joan test1

chgrp testteam test1


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File Management

ls (list) list files and directories

pwd (print working directory display full pathname of current directory

mkdir (make directory create new directories

cd (change directory) change to the directory

mv (move) move a file or directorycp (copy) copy a file or directory

rm (remove) remove a file and directory

touch update Timestamp on File

cat (concatenate) display files, or concatenate files

more control the display of files

ln (Link) create link file or directory
http://localhost/var/www/apps/conversion/releases/20121024195125/tmp/scratch_2/ahttp://localhost/var/www/apps/conversion/releases/20121024195125/tmp/scratch_2/fhttp://localhost/var/www/apps/conversion/releases/20121024195125/tmp/scratch_2/fhttp://localhost/var/www/apps/conversion/releases/20121024195125/tmp/scratch_2/fhttp://localhost/var/www/apps/conversion/releases/20121024195125/tmp/scratch_2/ahttp://localhost/var/www/apps/conversion/releases/20121024195125/tmp/scratch_2/a


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Listing Contents

ls [options] dirname list the contents of dirname

options:

-a list all files including hidden files

[hidden files are preceded by a .; eg .cshrc]

-l long listing showing ownership, permissions and links

examples:

ls /home/user/temp view the contents of a directory with absolute

pathname /home/user/temp

ls ../../temp list the contents of a directory using a relativepath.

pwd display full pathname of current directory


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Make Directory

mkdir dirname create the directory dirname

examples:

mkdir work create the directory work/ in the current working

directorymkdir work/proj1 create the directory proj1/ in the work/ directory

mkdir /wrk/user2 create the directory user2/ in the /wrk/ directory


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Change Directory

cd change to your home directory

cd dirname change to the directory dirname

examples:

cd ~tom change to toms home directory

cd /wrk/user2 change to the directory /wrk/user2cd .. change to the parent directory

cd ../.. Get up two levels


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Moving or Renaming

mv [options]presname newname rename a file

mv [options] srcfile destdir move a file to another directory

options:

-i confirm overwrites

example:

mv ~user1/file ./outputfile moves file from user1s home directory to

the current working directory and renames it

output file

Note: Be careful when overwriting files!


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Copying

cp [options] srcfile destfile copy a file to another filename

cp [options] srcfile destdir copy a file to another directory

options:

-i confirm overwrites

-R recursively copy a directory and its contents,

copies symbolic links

example:

cp -R proj1 proj2 copy the directory proj1/ and name it proj2/

Note: Be careful when overwriting files!


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Removing

rm [options]filename remove a file

options:

-f remove without prompting

-i confirm removal

-r recursively remove a directory and its contents

example:

rm -rf /scratch/user2/dir1 remove the directory /scratch2/user2/dir1

and its contents

!!!WARNING!!! This will DELETE EVERYTHING in that directory!!!

You can not recover your files after you removed them (unlike Windows OS).


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Update Timestamp on File

touch [options]file update access and/or modification times of file

Options:

-a Changes the access time of the file

-m Changes the modification time of the file

-c Does not create the file if it does not already exist

Examples:ls -l-rw-r--r-- 1 user1 users 25936 Apr 24 09:53 firstfile-rw-r--r-- 1 user1 users 10245 Apr 24 09:53 secondfiletouch newfilels -l-rw-r--r-- 1 user1 users 25936 Apr 24 09:53 firstfile

-rw-r--r-- 1 user1 users 0 Apr 25 10:02 newfile-rw-r--r-- 1 user1 users 10245 Apr 24 09:53 secondfiletouch secondfilels l-rw-r--r-- 1 user1 users 25936 Apr 24 09:53 firstfile-rw-r--r-- 1 user1 users 0 Apr 25 10:02 newfile-rw-r--r-- 1 user1 users 10245 Apr 25 10:05 secondfile


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Catenate / Type

catfilename 1) displays the contents of file on the screen, one after

the other .

2) You can also use it to create files from keyboard input

as follows (> is the output redirection operator)

example:cat > hello.txt

hello world!

[ctrl-d]

ls hello.txt

hello.txtcat hello.txt

hello world!


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Catenate with pause

morefilename 1) displays the contents of file on the screen, pausing at the

end of each screenful and asking the user to press a key

2)You can also use more to break up the output of commands

that produce more than one screenful of output

example:more output.c

ls -l | more

(| is the pipe operator)


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Making links file

lnfilename linkname Make hard links from one file or directory to another

ln -sfilename linkname Make soft (or symbolic) links from one file or

directory to another

example:

ln -s hello.txt bye.txtls -l bye.txt

lrwxrwxrwx 1 will finance 13 bye.txt -> hello.txt


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Process Control


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Processes

A process is a program in execution identified by a unique PID (process

identifier).

Every time you invoke a system utility or an application program from a shell,

one or more "child" processes are created by the shell in response to your

command.

An important process that is always present is the init process. This is the first

process to be created when a UNIX system starts up and usually has a PID of 1.

All other processes are said to be "descendants" of init.

A process may be in the foreground, in the background, or be suspended.


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Listing Process

ps [options] display the status of the current processes and the process

id-number

options:

-e all processes now running

-u display processes owned by a particular user

jobs shows any jobs that are currently running in the background

or suspended


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Process Control

-C cancel a foreground job

-Z stop (interrupt) a foreground job

bg run stopped job in the background

fg run stopped job in the foreground

& appended to the end of a command will place that job in the

background

examples:

$ sleep 1000 &

$ man ls-Z

$ jobs

$ fg %2

$ jobs[2] + Stopped (SIGTSTP) man ls

[1] - Running sleep 1000 &

?


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Killing a process

kill id-number terminate a process owned by you; id-number

(process id) can be found with the ps command

or

kill %job-number terminate a process owned by you; job-number can

be found with the jobs command

Example:

ps

PID TTY TIME CMD

17717 pts/10 00:00:00 bash

27501 pts/10 00:00:01 find

27502 pts/10 00:00:00 ps

kill 27501

kill -9 27501 If a process refuses to be killed, uses the -9 option


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STDINT,STDOUT and STDERR

Reset

BreakStop

f1 f2 f 3 f4 f5 f6 f7 f8

Back

Space

ReturnCTRL

User

System

. / + -

7 8 9

4 5 6 ,

1 2 3

0 .

Menu

TabNextSelect

Prev

Insert

line

Delete

line

Insert Delete

char char

|

\

}

]

{

[

=

+

_

-

"

'

:

;

Shift

Extend

char

?

/

>

.

command output redirection (create new, overwrites existing file)

>> command output redirection (append)

Examples:

Create/Overwrite Create/Append

$ ls > filelist.out $ ls >> filelist.out

$ cat seq1 seq2 > seq $ cat seq1 >> seq2

(combine individual sequence files into one file)


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Error Redirection

2> error output redirection (create new, overwrites existing file)

2>> error output redirection (append)

Examples:

$ cp 2> cp.err Create/Overwrite

$ cp 2>> cp.err Create/Append

$ more cp.err

Usage: cp [-f|-i] [-p] source_file target_file

cp [-f|-i] [-p] source_file ...target_directory

cp [-f|-i] [-p] -R|-rsource_directory...target_directory

Usage: cp [-f|-i] [-p] source_file target_filecp [-f|-i] [-p] source_file ... target_directory

cp [-f|-i] [-p] -R|-r source_directory...target_directory


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pipes

command1 | command2 | directs standard output of one command into

standard input for the next command

examples:

ls -al | more look at the ls output one page at a time

cat hello.txt | sort | uniq creates three processes (corresponding to cat,

sort and uniq) which execute concurrently. As

they execute, the output of the who process is

passed on to the sort process which is in turn

passed on to the uniq process. uniq displays its

output on the screen (a sorted list of users

with duplicate lines removed).


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Introduction to vi


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Introduction to vi

vi is the standard UNIX text editor

very powerful

useful simple subset of commands

portable (PCs, mainframes, etc.)

designed for slow networks

full-screen

Starting vi

vifilename

Changes are stored in a buffer, so you must save to change the file

!If the file doesn't exist, vi will create it for you.


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Command mode

move cursor, save, delete text, quit vi, etc.

Last-line mode

Initiated from command mode by entering advanced editing

commands like :, /, ?, !.

Commands are shown on the status line (Bottom line )

Input mode

for inserting text

start by typing i; finish with ESC

cannot quit, delete, etc. in this mode

If in doubt, press ESCa few times. This will put you back in

command mode.

Three Modes


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Cursor movement

h left

j downk up

l right

^ beginning of line

$ end of line

1 G top of document

G end of document

G go to line

^F page forward

^B page backward

w word forwards

b word backwards

l


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Inserting and typing text

i insert text (and enter input mode)

a append text (and enter input mode)o start a new line (and enter input mode)

Move to insertion point

Switch to input mode: i

Start typing; BACKSPACE or DELETE for deletion

ESC finish; back in command mode

No RETURN


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Deleting

Backspace Delete character before cursor (only works in insert mode)

Must be in command mode

x Delete character that cursor is on.

dd Delete current line.

dd Delete n lines

D Delete from cursor position to end of line

:i,jd Delete lines i to j

:23,29d Delete lines 23 to 29

:.,$d Delete from current line to the end of file.

u Undo last command


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Deleting and moving

Cut & Paste with Deleted Text

dd or dd or D delete from screen and store text in a buffer

move cursor to new location

p paste contents of buffer to right of cursor position

Copy & Paste

yy or yy yank/copy lines and store text in a buffer

move cursor to new location

p paste contents of buffer to right of cursor position


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Searching for Text

There is one here

and one more here

and yet one more

but not this ONE

nor this One

/one

next

previous

n

N

a56686

type / and then a regular expression and pressEnter


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Global Search and replace

:s/old/new/g replace every occurrence of old by new

:i,js/old/new/g replace every occurrence of old by new between lines i and j

:s/Hat/Head/g

:2,200s/Andy/Andrew/g

:1,.s/fc/function/g from line 1 to current


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Finishing a vi Session

Get to command mode (press ESC)

:w save file (not quit):wq save file and quit

ZZ save file and quit

:q! quit without saving

:w! newfile save as the file 'newfile', overwriting any existing newfile


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Customizing Your Shell

Environment


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Shells and Shell Scripts

A shell is a program that takes your commands from the keyboard and gives them

to the operating system to perform.Shells also usually provide features such job control, input and output redirection

and a command language for writing shell scripts.

A shell script is simply an ordinary text file containing a series of commands in a

shell command language (just like a "batch file" under MS-DOS).

There are many different shells available on UNIX systems (e.g. sh, bash, csh, ksh

etc.), and they each support a different command language.


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View your login shell

Determine your login shell:

echo $SHELL

Change to another shell, just type the shell name:

sh (or csh or ksh or bash)

Or

exec sh (close the original shell, then open another shell sh)

Go back to your normal shell

exitorpress CTRL-D


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Changing your Login Shell

To change your Unix shell, you will need to be at a Unix shell prompt.

type the command

$ passwd -r nis -e

Enter login(NIS) password:

Type your Unix password and press return. You will then see screen output

similar to the following:

enter the full name of your new shell.

Old shell: /usr/local/bin/bashNew shell:


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Initialization files

Each time you login to a UNIX host, the system looks in your home directory forinitialization files. You can change your environment by changing initialization

files.

Shell System initializationfiles First

User initializationfiles secondly

Template/etc/skel

sh(Bourne

shell)

/etc/profile $HOME/.profile local.profile

ksh(Kornshell)

/etc/profile $HOME/.profile$HOME/.kshrc

local.profile

csh(C shell) /etc/.login $HOME/.cshrc$HOME/.login

local.cshrclocal.login

bash(BourneAgain shell )

/etc/profile $HOME/.bash_profile$HOME/.bashrc

local.profile

$HOME/.cshrc

$HOME/.login


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Setting shell variables

At login the C shell first reads .cshrc followed by .login

.login is to set conditions which will apply to the whole session and to performactions that are relevant only at login.

.cshrc is used to set conditions and perform actions specific to the shell and to

each invocation of it.

The guidelines are to set ENVIRONMENT variables in the .login file and SHELLvariables in the .cshrc file.

Setting shell variables in the .cshrc file

$ vi ~/.cshrcAdd the following line AFTER the list of other commands

set history = 200Save the file$ source .cshrc (force the shell to reread its .cshrc file )$ echo $history (Check this has worked)


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Setting Environment Variables

View all system variables by the command env

By convention system variables are capitalized

PATH a list of directories that the shell uses to locate executable files for commands

HOME Name of your home (login) directory

PWD Current directory

OLDPWD Previous directory before the last cd command

Setting system variables differs by shell. bash uses export, csh uses setenv

varname=value command

export varnames

Example:PATH=$PATH:/sbin:/usr/sbin:/usr/bin:/etc:/usr/ucb:/local/bin

EDITOR=/usr/local/bin/emacs

export EDITOR PATH


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Alias

alias new=original defines new to be an alias for original (ksh or bash)

alias new original (csh)

example:

alias ct=cleartool

alias ll='ls l'

alias logout='. ~/.ksh_logout; exit'


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h d


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tar (tape archive) ; create archives

compress compress files

gzip compress files

find find files and directories with a wealth of search criteria

grep (general regular expression parser); text search

sort sort information provided on standard inputssh (secure shell) ; remote login

A hi d S


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Archives and Storage

tar create archives, and read/write from tapes and diskettes

tar -cvf archivenamefilenames create a disk file tar archive

tar -tvf archivename list the contents of a tar archive

tar -xvf archivename restore files from a tar archive

compress /gzip compress files

compressfile compressfile and rename itfile.Z

uncompressfile.Z uncompressfile.Zand rename itfile

gzipfile compressfile and rename itfile.gz

gunzipfile.gz uncompressfile.gzand rename itfile

Fi di Fil


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Finding Files

find Find files and directories with a wealth of search criteria

Example:

find directory-name targetfileprint

look for a file called targetfile in any part of the directory tree rooted at

directory.

find /home -name "*.txt" -print 2>/dev/null

search all user directories for any file ending in ".txt" and output any matching

files. The 2>/dev/null suppresses error messages.

find . -name "*.txt" -exec wc -l '{}' ';'

counts the number of lines in every text file in and below the current directory.

The '{}' is replaced by the name of each file found and the ';' ends the -exec

clause.

S hi T t


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Searching Text

grep options patternfiles searches the named files (or standard input if no

files are named) for lines that match a given pattern

Options:

-c (print a count of the number of lines that match)

-i (ignore case)

-v (print out the lines that don't match the pattern)

-n (printout the line number before printing the matching line)

S hi T t ( t )


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Searching Text (cont.)

Examples:

grep -vi hello *.txt searches all text files in the current

directory for lines that do not contain

any form of the word hello

(e.g. Hello, HELLO, or hELlO).

grep hello `find . -name "*.txt" -print` search all text files in the directory tree

rooted at the current directory for lines

containing the word "hello".

grep ^..[l-z]$ hello.txt matches any line in hello.txt thatcontains a three character sequence that

ends with a lowercase letter from l to z.

S ti g fil


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Sorting files

sort [options]filenames sort information provided on standard input

Options:

-r Reverses the sense of comparisons

Examples:

sort input1.txt input2.txt > output.txt

outputs the sorted concentenation of files input1.txt and input2.txt to the file

output.txt.

sort input.txt | uniq > output.txt

Uniq removes duplicate adjacent lines from a file input.txt. It is most useful

when combined with sort

Remote login


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Remote login

ssh [options] host secure shell; a program for logging into a remote

host providing encrypted communications

between hosts

options:

-l login name

-X sets environment variables for porting X-display

example:

ssh -l fengy sbardy12 open a secure connection for the user fengy on the

host sbardy12

ssh load2 open a secure connection to host load2 with current

username


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UNIX Fundamentals 2010