© 2008 Wipro Ltd - Confidential UNIX 1.1 UCF - Course Content.

© 2008 Wipro Ltd - Confidential

UNIX 1.1 UCF - Course Content


UNIX Operating System


• OS is a system software

• OS provides an environment for execution of programs

• OS acts as an interface between the user and the hardware of the computer system.

• Kernel is the Core of the OS

• Unix kernel program is a combination of 2 programs genunix (generic unix) and unix.

Operating System (OS)


Features of UNIX

• Multi-user, multitasking, timesharing• Portability• Modularity• File structure• Security


Layered Architecture

HARDWARE

KERNEL

SHELL


Unix File System - DirectoriesDirectory Description

/ Primary hierarchy root and root directory of the entire file system hierarchy.

/bin/Essential command binaries that need to be available in single user mode ; for all users, e.g., cat, ls, cp.

/etc/ Host-specific system-wide configuration files

/home/Users‘ home directories , containing saved files, personal settings, etc.; normally a separate partition.

/opt/ Optional application software packages .

/sbin/ Essential system binaries, e.g., init, ip, mount.

/tmp/ Temporary files

/usr/Secondary hierarchy for read-only user data; contains the majority of (multi-)user utilities and applications.


UNIX Commands


Login and authentication

login access computer; start interactive session

logout disconnect terminal session

passwdchange local login password; you must set a strong password that is not easily guessed

sudo allows users to run programs with the security privileges of another user (normally the superuser, or root)


date show date and time

history list of previously executed commands

man show online documentation by program name

who who is on the system and what they are doing

whoami who is logged onto this terminal

top show system stats and top CPU using processes

uptime show one line summary of system status

Information


cat combine files

cp copy files

ls list files in a directory and their attributes

mv change file name or directory location

rm remove files

ln create another link (name) to a file

chmod set file permissions

chown Change ownership of file/directory

gzip, gunzip compress/decompress a file

find find files that match specific criteria

File management


cat copy files to display device

more show text file on display terminal with paging control

head show first few lines of a file(s)

tail show last few lines of a file; or reverse line order

vi full-featured screen editor for modifying text files

grep display lines that match a pattern

diff compare two files and show differences

file examine file(s) and guess type: text, data, program, etc.

wc count characters, words, and lines in a file

Display contents of files


cd change to new directory

mkdir create new directory

rmdir remove empty directory (you must remove files first)

mv change name of directory

pwd show current directory

Directories


df summarize free space on disk filesystems

du show disk space used by files or directories

Disks


* match any characters in a file name

~user shorthand for home directory of user

$name substitute value of variable name

\ turn off special meaning of character that follows

' in pairs, quote string with special chars, except !

" in pairs, quote string with special chars, except !, $

` in pairs, substitute output from enclosed command

Special character handling


& run job in background

^c kill job in foreground

^z suspend job in foreground

fg restart suspended job in foreground

bg run suspended job in background

; delimit commands on same line

ps show process information

kill kill background job or previous process

Controlling program execution


tee copy input to both file and next program in pipe

script make file record of all terminal activity

Controlling program input/output

lpr send file to print queue

lpq examine status of files in print queue

lprm remove a file from print queue

Printing (BSD based)


ssh remote login/command execution; encrypted

scp remote non-interactive file copy; encrypted

sftp remote interactive file copy; encrypted

telnetremote network login; plain text password - not recommended

ftpnetwork file transfer program; plain text password - not recommended

Networking/communications


• Two modes of the vi editor

– Command mode: Can perform commands in the vi editor(default mode)

– Editing (Insert) mode: Can type information in the vi editor

• Why learn the vi editor?

– The vi editor is the most frequently used editor in all flavors of Linux and UNIX

– It is also useful in case the flavor of Linux/UNIX does not have a graphical interface

VI Editor


Some Simple VI Commands

j move cursor down one line

k move cursor up one line

h move cursor left one character

l move cursor right one character

u UNDO WHATEVER YOU JUST DID; a simple toggle

i insert text before cursor, until <Esc> hit

a append text after cursor, until <Esc> hit

o open and put text in a new line below current line, until <Esc> hit

O open and put text in a new line above current line, until <Esc> h

:q Quit a file ( use : q! for forceful quit without saving)

:w Save a file


• Refers to the permissions associated with a file with respect to the following

• Permission Levels• User (owner) (u)• Group (wheel, staff, daemon, etc.) (g)• World (guest, anonymous and all other users) (o)

• Permission Settings• Read (r)• Write (w)• Execute (x)

File Access Permissions


• chmod u+x file_nameSyntax:

chmod <category> <operation> <permission> <filename(s)>

or chmod <octal number> filename

Octal Number4 - for read2 - for write1 - for execution

$ chmod 744 xyzthis sets read, write and execute permissions for owner, read permission for group and others

Changing Permissions - chmod


Command Syntax mkdir [OPTION] DIRECTORY rmdir [OPTION] DIRECTORY

$ mkdir(rmdir) <path>/<directory>$ mkdir(rmdir) –p <directory1>/<directory2>/<directory3>

Example:$ mkdir project1

This creates a directory project1 under current directory

$ mkdir –p project2/project1This creates 2 level of directories

$rmdir –p dir1/dir2/dir3Remove the directory recursively

Directory Creation/Removal


Command - cd

cd command is used to change the directory

• cd - take to the home directory

• cd .. - takes to the parent directory

• cd / - takes to the root directory

• cd ~user - takes to the user home directory.


File-Related Commands

File Operation Command

Copying a file cp

Moving a file mv

Removing a file rm

Displaying a file and concatenating files cat

Used to copy files across directories

Syntax

cp <source file> <new file name>

Example

cp file1 file2

Command - cp


Options to cp• -p

• Copies the file and preserves the following attributes• owner id• group id• permissions• last modification time

-r • recursive copy; copy subdirectories under

the directory if any-i

• interactive; prompts for confirmation before overwriting the target file, if it already exists

Command - cp


Used to move a file, or rename a file

Preserves the following details• owner id• group id• permissions• Last modification time

-f suppresses all prompting (forces overwriting of target)

-i prompts before overwriting destination file

Command - mv


Used to remove a file• Syntax : rm file(s)

-f suppresses all prompting

-i prompts before deleting destination file

-r will recursively remove the file from a directory (can be used to delete a directory along with the content )

Caution: Use “i” option along with “r” to get notified on deletion

Command - rm


$ ls –l-rwxr-xr-x 1 user1 training 12373 Dec 15 14:45 a.out-rwxr-xr-x 3 user1 faculty 4096 Dec 24 11:56 awkpro

$chown user2 a.out

$ls –l -rwxr-xr-x 1 user2 training 12373 Dec 15 14:45 a.out-rwxr-xr-x 3 user1 faculty 4096 Dec 24 11:56 awkpro

$ chgrp training awkpro

$ls –l-rwxr-xr-x 1 user2 training 12373 Dec 15 14:45 a.out-rwxr-xr-x 3 user1 training 4096 Dec 24 11:56 awkpro

Command – chown & chgrp


Linking files

• Hard Link (in the same filesystem)• $ ln /usr/bin/clear /usr/bin/cls

• Hard link uses the same inode number

• Soft Link (in different filesystems also used to link directories)• $ ln –s /usr/bin/clear /home/user1/cls

Command - ln


• Standard Input file• Keyboard, file descriptor is 0

• Standard Output file• Monitor, file descriptor is 1

• Standard Error file• Monitor, file descriptor is 2

Standard Files


< file redirect standard input from file

> file redirect standard output to file

2> file redirect standard error to file

2>&1 merge standard error with standard output

$ cat > abc

$ ls –l > outfile

$ cat xyz abc > outfile 2> errfile

$ cat xyz abc > outfile 2>&1

I/O Redirection


• Filters are programs that takes its input from the standard input file, process it, and sends it to the standard output file.

• Commonly used filter commands• sort• grep• cut• head• tail• paste

Filters


Sorts the contents of the given file based on the first char of each line.-n numeric sort (comparison made

according to strings numeric value)

-r reverse sort

Example: $ du /home | sort –nr

list files from /home in decreasing order of their file size

• grep -Global Regular Expression Printer is used for searching regular expressions

• Syntax• grep <options> <pattern> <filename(s)>

grep (global regular expression print)

sort


-c displays count of line where the pattern occurs-n displays line numbers along with the lines-v displays all lines except lines matching

pattern-i Ignores case for matching

Patterns: * matches 0 or more characters

^pqr Matches pqr at the beginning of the line

pqr$ Matches pqr at the end of the line

“.” Matches any one character

grep options


head: Displays the first n lines of the file

$ head -3 file1

tail:Displays the last n lines of a file

$ tail -3 file1

Can also specify the line number from which the data has to be displayed till the end of file

$ tail +5 file1

Filter Command – head / tail


• Allows the output (only the standard output) of a command to be sent as input to another command.

• Multiple pipes may appear in one command line.

Example:

$ cat file1 | head | wc -l

Command Piping


• File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to exchange files between computers

• FTP service runs on Port 21

• Ftp program supports the following commands get receive file from host mget receive multiple files from host put send file to host mput send multiple files from host

ftp - commands


Ftp program supports the following commands as well ls list directory of host cd change directory on the host lcd change directory on the local machine

To set transfer format asc / ascii set to ascii mode bin/ binary set to binary mode

Progress indication of transfer (to see the data flow) hash command

Quitting ftp session bye command

ftp - commands


• Tar is an archiving utility to store and retrieve files from an archive, known as tar file.

• Archives and extracts files to and from a single file called a tar file.

• Though archives are created on a tape, it is common to have them as disk files as well.• SYNTAX

tar c|t|x [vf destination] source...

c – create a tar file t – list the contents of the tar file x – extract the contents of the tar file.

Tape Archive - tar


Examples:• $ tar –cvf my.tar *.dat

Create a new tar file containing all .dat files (assuming a.dat, b.dat and c.dat exist)

• $ tar –xvf my.tar Extract the contents of the tar file my.tar

• $tar -c file1 file2 write the file1 and file2 files to a new archive on the default tape drive

• $tar -xf my.tar test.file Extract test.file from the tar file my.tar

• $tar –tvf my.tar view the contents of the tar file called my.tar

Tape Archive - tar


• Lets user to search set of files and directories based on various criteriaSyntax: find [path...] [expression]

[path] where to search

[expression]• What type of file to search (specified with –type option)• What action to be applied (–exec, –print, etc.)• Name of the files (specified as part of –name option, enclosed in “ “)

Examples

• $ find . –name “*.c” -printlists all files with .c extension from the current dir & its

subdirectories

• $ find /etc -name hostsWill find the file named “hosts” under /etc and print --- /etc/hosts

find


• $ find /home lists all files and directories under /home

• $ find . –atime 2 lists files accessed exactly 2 days ago

• $ find . –atime +2 lists files accessed more than 2 days ago

• $ find / –mtime –2 lists files modified less than 2 days ago

find


• Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline).

• But it is sed's ability to filter text in a pipeline which particularly distinguishes it from other types of editors.

Example 1: command to change a to A and b to B in a file called ‘test’ is - #sed -e 's/a/A/' -e 's/b/B/' test

Example 2: find and replace the word “star" to “planet" globally in the file called ‘universe’ is - #sed '/s/star/planet/g' universe

Sed


• The iostat utility displays kernel I/O statistics on terminal, device and cpu operations.Example : Display tty statistics every 10 seconds – $ iostat –t 10

• netstat - Display network connections, routing tables, interface statistics, masquerade connections, and multicast memberships Example : command to display the Interface statistics - $ netstat –i and command to display routing table - $ netstat –nr

• vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.Example : To display five summaries at 2-second intervals - $ vmstat 2 5

IOSTAT / NETSTAT / VMSTAT


• ‘at’ : In Unix the at command is used to schedule other to be executed once, at a particular time.More precisely, it reads a series of commands from standard input and collects them into one "at-job" which is carried out at a later date.

Example : $ echo "cc -o test test.c" | at 1145 $ at 1145 jan 31

at> cc -o test test.c at> ^D

‘Cron’ : is a time-based job scheduer in Unix. Cron enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates. It is commonly used to automate system maintenance or administration.

Example : command t list all cronjobs - $ crontab –l, command to execute a cron job - $ crontab –e <job name> and command to remove a cron job - $ crontab –r <job name >

Job Scheduling


• Process - a program in execution• When program is executed, a new process is created• The process is alive till the execution of the program is complete• Each process is identified by a number called pid• The ps command is used to display the characteristics of a process• It fetches the pid, tty, time, and the command which has started the process.

-f lists the pid of the parent process also. -u lists the processes of a given user -a lists the processes of all the users -e lists all the processes including the system processes

• Back Ground process :

Enables the user to do more than one task at a time.

If the command terminates with an ampersand (&), UNIX executes the command in the background

nohup

– Lets processes to continue to run even after logout

– The output of the command is sent to nohup.out if not redirected

Unix Process and PS


• kill: Kills or terminates a process• kill command send a signal to the process

The default signal is 15 ( SIGTERM) • kill -9 (SIGKILL)

Terminates the process abruptly• pkill : command used to kill a process by name

pkill <command name> Pkill -9 <ommand name>

• ‘top’ Comamnd : Provides an ongoing look at processor activity in real time. It displays a listing of the most CPU-intensive tasks on the system, and can provide an interactive interface for manipulating processes.

• ‘nice’ Command : The nice command lets you run a command at a priority lower than the command's normal priority. If you do not specify an Increment value the nice command defaults to an increment of 10. The priority of a process is often called its nice value.

Killing a Process, TOP and NICE


Date post:	29-Dec-2015
Category:	Documents
Upload:	randell-long
View:	222 times
Download:	1 times

© 2008 Wipro Ltd - Confidential UNIX 1.1 UCF - Course Content.

Documents