fundamentals of unix - for freshers

7/29/2019 Fundamentals of Unix - For Freshers

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LogicaCMG 2006. All rights reserved1

Introduction to Unix

Gopan Nair

Systems Manager Financial Services


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Schedule

Overview of Unix

Login Process

Learning the basic commands

Getting Help

Customizing the shell environment Understanding file permissions

Job Control


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Schedule

Using the vi editor

Regular expressions and pattern matching

Shell programming (Bourne shell)


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What Is an Operating System?

Operating

System

Users

Programs

Consumers

Disks

Memory

CPU

Network

Printers

Resources


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Historyof the UNIX Operating System

UNIX is originally developed at AT&T Bell Laboratories in 1969 by Ken Thompson

In 1973, Unix was re-written in C language. This led to its popularity

In 1983, Bell Lab announced their support for a new version, known as System V.

By this time, University of California at Berkeley had also developed a new variant of Unix,

known as 4.3 BSD.

The 4.3 BSD provided new features such as reliable signals and TCP/IP.

Neither AT&T nor BSD is now active in Unix developmentso most new developments are

now defined by a specific vendor or a body such as IEEE (POSIX standard), FreeBSD

organization or the Linux community.


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Different Flavours of Unix?

Product From Processor

AIX IBM PowerPC

HP UX HP PA-RISC/ITANIUM

Solaris Sun SPARC

Tru64Unix Compaq Alpha

IRIX SGI MIPS

LINUX Freeware Intel

SCO Unix SCO Intel

NCR MP-RAS NCR Motorola/Intel


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Features of UNIX

Hierarchical file system

Multi-tasking

Multi-user

Provides more than one type of shells (command interpreters)

Provides more than one mechanism for inter-process communication (IPC)

Excellent networking support through TCP/IP

Portability


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Unix Architecture


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What Defines a User Account?


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Creating a User Account

#useradd


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passwd Assigns a login password

$ passwdChanging password for user3Old password:

New password:Re-enter new password:

minimum of six characters

at least two alpha characters

at least one non-alpha character

Setting Your Password


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Your Login Process

When you log in successfully, the first program started is the shell, orcommand line interpreter. Now that you have logged in you shouldsee a $ prompt awaiting commands. This program gives you amethod of communicating with the operating system to run andmanage other programs.

For the login shell process, Unix makes yourhome directory as thecurrent directory.

Therefore, after login, by default, you will be working with your home

directory.


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Your Login Process

At login time, each shell reads one or more initialization files from your homedirectory. These files give you the opportunity to set environment variables

The name of this script depends upon the login shell. For Bourne shell, this file is.profile file. For C-shell, this file is .cshrc file.

To customize your login environment, you can modify these startup scripts.


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The Shell Command Interpreter

Functions of a Shell:

After login you are presented with a shell prompt which waits

for you to type commands Validates the command entered by

the user.

Once the return key is pressed, the shell processes the command

When the command is finished, the shell re-displays the prompt.

This process continues until the user exits the shell, by typing exit

or by pessing ctrl-d, at which time the user is logged out of theUNIX host


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Basic Unix Commands


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Using Unix Commands

Most Unix commands are individual programs that perform various tasks. Unixhas a large set of commands that are described related reference (man) pages.

When you enter a command, the shell interprets the command, and then gives anappropriate response -- that is, the system either runs the program or displays an

error message.

If the command is valid, the shell directs the operating system to do what isrequested.

Note: Unix is case sensitive


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Getting Help

The UNIX reference manual is divided into eight numbered

sections:

1. General User Commands

2. System Calls

3. User-level Library Functions

4. Device Drivers, Protocols

5. File Formats

6. Games (rarely available)

7. Document Preparation

8. System AdministrationYou can see the command summary for each section by typing:

man #intro where # is one of the eight section numbers


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Syntax:

man [-k| X ] keyword | command

in which Xis the number of one of the manual sections

Examples:

$ man date$ man -k copy $ apropos copy $ man passwd $ man 4 passw

Use to view next page.

Use to view next line.

Use to quit the man command.q

Space

Return

The Online Manual


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General commands

stty set terminal options

date display or set the date

ps display information about processes

env display or change current environment

id Display you user and group identificationswho dentify other users logged on to the system

echo Display simple messages to your screen.

clear Clears terminal screen.


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The stty Command

stty reports or sets terminal control options

$stty -aspeed 9600 baud; 45 rows; 107 columns;

eucw 1:1:0:0, scrw 1:1:0:0:intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ^@

eol2 = ^@; start = ^Q; stop = ^S; susp = ^Z; dsusp = ^Y; reprint = ^R

$ stty erase ^H to change the erase character from ^? (the delete key) to ^H$ stty echo To stop the display of the characters typed$ stty echo


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The date Command

Date [options] [+format] Displays or sets the date or time

Common Options

-u use Universal Time (or Greenwich Mean Time)+format specify the output format

%a weekday abbreviation, Sun to Sat

%j day of year, 001 to 366%t %y last 2 digits of year, 00 to 99%D MM/DD/YY date

$ date mmddHHMM[yy] sets the system date$date +%a%t%DMon 06/10/96

$date '+%y:%j'96:162


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id Displays user and group identification for session

$iduid =303 (user3) gid=300 (class)

The id Command


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who [am i] Reports information about users who arewhoami currently logged on to a system

$ whoroot tty1p5 Jul 01 08:01user1 tty1p4 Jul 01 09:59user2 tty0p3 Jul 01 10:01

$ who am i

user2 tty0p3 Jul 01 10:01

$ whoamiuser2

$ tty Prints the name of the tty line

The who Command


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The echo Command

echo [ String ... ]Writes character strings to standard output

$ echo Hello Class or echo "Hello Class

Hello Class

$ echo \n Hello Class

$ echo $PATH


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clear Clears terminal screen

cls

The clear Command


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sbin usr dev etc var stand

profilegroup

user1 user2 user3

= directory

= file

passwd

opt hometmp

bin contrib local sbinlib vueshare

mail news tmp vue

vi

man

cp ls man sh tar

vmunix

The File System Hierarchy


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Monitoring Disk Usage

Monitor available file system space with df:

# df

Filesystem

/dev/vg00/lvol5

/dev/vg00/lvol4

/dev/vg01/myfs1

/dev/vg01/myfs2

Determine space used by directory subtrees with du:

# du -sk /myfs2/*

844 /myfs2/data1

1327 /myfs2/data2

1073 /myfs2/data3

10757 /myfs2/data4

4 /myfs2/lost+found

kbytes

294912

24576

16384

15893

used

261523

19333

1174

14006

avail

31352

4978

14331

297

%used

89%

80%

8%

98%

Mounted on

/opt

/home

/myfs1

/myfs2


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Name of current working directory

The directory in which you are working at any given time is yourcurrent, orworking directory.

If you are uncertain about the directory in which you are working, enter the (print working directory) command.

You can use the cd command to move to your home directory from any location.


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Understanding pathnames

A pathname specifies the location of a directory or a file within the filesystem.

A pathname consists of a series of directory names separated by

slashes ( / ) that ends with a directory name or a file name.

A pathname that starts with a slash ( / ) is called a full pathname or an

absolute pathname.

A pathname that starts without a slash ( / ) is called a relative

pathname


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Understanding Absolute pathnames

You can also think of a full pathname as the complete name of a file or adirectory in relation to the root (/) directory.

Regardless of where you are working in the file system, you can alwaysfind a file or a directory by specifying its full pathname.


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Understanding Relative Pathnames

The file system also lets you use relative pathnames. Relativepathnames do not begin with the / that represents the root directorybecause they are relative to the current directory.

You can specify a relative pathname in one of several ways:

As the name of a file in the current directory or with the name of a directoryone level below your current directory.

As a pathname that begins with .. (dot dot, the relative pathname for theparent directory).

As a pathname that begins with . (dot, which refers to the current directory).This relative pathname notation is useful when you want to run your ownversion of an operating system command in the current directory (for

example ./ls).


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Understanding directories

In Unix, a directory is a file that has a number of entries. Each entrycontains:

A filename

The I-node number of the file

Every directory contains at least two entries:

Filename of .. (dot dot)

Filename of. (dot)


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Understanding directories

In the C shell and the Korn or POSIX shell, you may also use a tilde ( ~) at thebeginning of relative pathnames.

The tilde character used alone specifies your home directory. The tilde characterfollowed by a user name specifies the home directory of that user. For example,

$ cd ~/mydir

$ cd ~micky/mouse


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pwd

ls

cd

find

mkdir

rmdir

Displays the directory name of your current location in the hierarchy.

Sees what files and directories are under the current directory.

Changes your location in the hierarchy to another directory.

Finds files.

Creates a directory.

Removes a directory.

Basic File System Commands


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ls [-adlFR] [pathname(s)]

$ ls

f1 f2 memo$ ls -Ff1 f2* memo/$ ls -aFprofile f1 f2* memo/$ ls memo

f1 f2$ ls -F /homeuser1/ user2/ user3/$ ls -F ../user2f1

ls List Contents of a Directory


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cd [ ]dir_pathname

$ pwd/home/user3$ cd memo; pwd/home/user3/memo$ cd ../..; pwd/home$ cd /tmp; pwd/tmp$ cd; pwd/home/user3$ cd -

cd Change Directory


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findpath_list expression

$ find . -name .profile./.profile$

Performs an ordered search through the file system.

path_list is a list of directories to search.expression specifies search criteria and actions.

The find Command


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The find Command More options

Option Description-amin n file was last accessed nminutes ago

-atime n file was last accessed 24*nhours ago

-empty file is empty and is either a ordinary file or a directory

-exec execute commands

-mtime n file was last modified n*24 hours ago

-size n[ck] size of file is n512 byte blocks (c bytes, k kilobytes)

-user unametrue if file belongs to uname


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mkdir [-p] dir_pathname(s)

rmdir dir_pathname(s)

$ pwd/home/user3

$ mkdir fruit

$ mkdir fruit/apple

$ cd fruit

$ mkdir grape orange

$ rmdir orange

$ cd ..$ rmdir fruit

rmdir: fruit not empty

$ rmdir fruit/apple fruit/grape fruit

mkdir and rmdir Create and Remove Directories


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Disk usage summary: du

du - summarizes disk space usage$du sk *

538873 WL8.1

50150 jre130

2 logs1 registry.xml

346190 tuxedo8.0

282596 wl61

$ du

sk .


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File

Directory

Tree

Path name

HOME

pwdcdlsfind

mkdirrmdir

A container for data

A container for files and other directories

Hierarchical structure of a UNIX system

Identifies a file's or directory's location in the hierarchy

Represents the path name of your login directory

Displays your current location in the hierarchyChanges your location in the hierarchy to another directory

Lists the contents of a directory

Finds files specified by options

Creates directories

Removes directories

The File SystemSummary


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A container for data or a link to a device.

Every file has a name and may hold data that resides on a disk.

There are several different types of files:

Regular files

text, data, drawings

executable programs Directories

Device files

What Is a File?


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Manipulating files and directories

In Unix, each file is a series of bytes without any structure (format). The directory isthe only file that has a structure imposed on it.

Each file has one or more names. Each file is also stored in a directory. Thedirectories are stored in the file system.

A file system is the useful arrangement of files into directories.


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Listing files and directories

In Unix, each file has a number of attributes associated with it. Some ofthese are:

File type File permissions

File owner user ID and group ID

File size

Date/time of creation, last update and last access

Number of hard links


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File names

A file name can contain any character except the following because these havespecial meaning to the shell:

Slash ( / )

Backslash ( \ )

Ampersand ( & ) Left- and right-angle brackets (< and >)

Question mark ( ? )

Dollar sign ( $ )

Left bracket ( [ )

Asterisk ( * )

Tilde ( ~ )

Vertical bar or pipe symbol ( | )


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File names

You may use a period or dot ( . ) in the middle of a file name. If you use a dot atthe beginning of the file name it will be hidden when doing a simple listing of filesthru the ls command.

The maximum length of a file name depends upon the file system used. Most newfile system allow a maximum length of 255 characters (the default). Older filesystems allow a maximum file name length of only 14 characters.


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Following are some of the file types:

- (hyphen) for ordinary files

b for block-special files

c for character-special files

d for directories

l for symbolic links

p for pipe-special files (first in, first out)

s for local sockets


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How do I create files?

vi touch

I/O redirection

Examples:$ ls -Rl / > allfiles$ cat test.c > copytest.c

echo

Examples:$ echo testing > file

ln


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touch Create a file

Syntaxtouch[options] [date_time] file

touch[options] [-t time] file

Common Options

-a change the access time of the file (SVR4 only)

-c dont create the file if it doesnt already exist

-f force the touch, regardless of read/write permissions

-m change the modification time of the file (SVR4 only)

-t time use the time specified, not the current time (SVR4 only)

When setting the "-t time" option it should be in the form:

[[CC]YY]MMDDhhmm[.SS]

Examples

To create a file:

$ touch filename


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lscat

morelesshead

tailwcuniqlpcp

mv

mvlnrmfilestrings

Look at the characteristics of a file

Look at the contents of a file

Look at the contents of a file, one screenful at a time

more versatile paginate than more

display the first few lines of a file

displays the last part of a filedisplay a count of lines, words and characters in a file

remove duplicatelinesPrint a file

Make a copy of a file

Change the name of a file or directory

Move a file to another directory

Create another name for a file

Remove a file

determine the type of file

to search a binary file for printable, ASCII characters

What Can We Do with Files?


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1. Number of 512-byte blocks used by files in this directory.

2. Number hard of links to each file.

3. User name of the file's owner.

4. Group to which the file belongs.

5. Number of bytes in the file.

6. Date and time the file was created or last modified.

7. Name of the file or directory.

Examples:$$ls -ltotal 4 [1] [2] [3] [4] [5] [6] [7]

-rw-r--r-- 1 larry system 101 Jun 5 10:03 file1



-rw-r--r-- 1 larry system 65 Jun 5 10:06 file3drwxr-xr-x 2 larry system 32 Jun 5 10:07 project


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cat [file...] Concatenate and display the contents of file(s)

$ cat remind

Your mother's birthday is November 29.$ cat note remindTO: Mike SmithThe meeting is scheduled for July 29.Your mother's birthday is November 29.$ catabc

1234

abc1234 CTRL + D

cat Display the Contents of a File


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more [filename]... Display files one screen at a time

$ more funfile...

--funfile (20%)--Q or q

Return

Space

more Display the Contents of a File


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less - opposite of more

less [filename]... less is a more functional clone of more provided bythe GNU project .One added feature of less is that it allows you to scroll backand forth in a file one line at a time with the arrow keys. less reads filesincrementally, rather than loading each file into memory like more, so lessuses less memory.

$ less funfile...

:Q or q


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head [-n] [filename]... display first few lines of file(s)

$ head /var/log/messages

$ head -12 /var/log/messages

head Display the End of a File


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tail [-n] [filename]... Display the end of file(s)

$ tail -1 notesoon as it is available.$ tail f [filename]... tracks the file, printing out every new line as it is added.

tail Display the End of a File


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wc [OPTION]. . . [FILE]. . .

-c count bytes-m count characters (SVR4)-l count lines-w count words

If no options are specified it defaults to "-lwc".

$wc l /etc/passwd

wc Print the number of bytes, words, and lines in files


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uniq - remove duplicate lines

uniq[options] [+|-n] file [file.new]

d one copy of only the repeated lines

-u select only the lines not repeated+n ignore the first n characters-s n same as above (SVR4 only)-n skip the first n fields, including any blanks (space &tab)-f fields same as above (SVR4 only)

$uniq3 /etc/passwd

The -n option of the uniqcommand is used to skip the first 3 fields in file, and filter outlines which are duplicates from the 4th field onward.


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cp [-i] file1 new_file Copy a filecp [-i] file [file...] dest_dir Copy files to a directorycp -r [-i] dir [dir...] dest_dirCopy directories

$ ls -Ff1 f2* memo/ note remind$ cp f1 f1.copy$ ls -F

f1 f1.copy f2* memo/ note remind$ cp note remind memo$ ls -F memonote remind

cp Copy Files


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mv [-i] file new_file Rename a filemv [-i] file [file...] dest_dir Move files to a directorymv [-i] dir [dir...] dest_dir Rename or move directories

$ ls -F $ mv note remind memof1 f2* memo/ note remind $ ls -F$ mv f1 file1 file1 memo/$ ls -F $ls -F memo

file1 f2* memo/ note remind file2* note remind$ mv f2 memo/file2 $ mv memo letters$ ls -F $ ls -Ffile1 memo/ note remind file1 letters/$ ls -F memofile2*

mv Move or Rename Files


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cmp compare file contents

Syntax

cmp[options] file1 file2 [skip1] [skip2]

Common Options

-l report on each difference

-s report exit status only, not byte differences

Examples

Given the files file1 and file2

apple orange

grape mango

red red

blue blue

green yellow

The comparison of the two files yields:

$ cmp file1 file2

The default it to report only the first difference found.


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diff reports all differences between files

Syntax

diff [options] file1 file2

Common Options

-b ignore trailing blanks

-i ignore the case of letters

-w ignore and characters

-e produce an output formatted for use with the editor, ed

-r apply diff recursively through common sub-directories

Examples

For the mon.logins and tues.logins files above, the difference between them is given by:

$ diff file1 file2

The output lists the differences as well as in which file the difference exists. Lines in thefirst file are preceded by "< ", and those in the second file are preceded by "> ".


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rm [-if] filename [filename...] Remove filesrm -r[if] dirname [filename...] Remove directories

$ ls -Ff1 f2 fruit/ memo/$ rm f1$ ls -Ff2 fruit/ memo/

$ rm -i f2f2?


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$ ls -l f1

-rw-rw-r-- 1 user3 class 37 Jul 24 11:06 f1

$ ln f1 /home/user2/f1.link

$ ls -l f1

-rw-rw-r-- 2 user3 class 37 Jul 24 11:06 f1

$ ls -l /home/user2

-rw-rw-r-- 2 user3 class 37 Jul 24 11:06 f1.link

$ ls -i f1 /home/user2/f1.link

1789 f1 1789 /home/user2/f1.link

ln file new_file Link to a fileln file [file ...] dest_dir Link files to a directory

/

home

user3

f1

user2

f1.link

You are here.

This is a samplefile to be copied.

ln Link Files


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Hard Links

Directory/mydir

f1 101

file1 101

ln /mydir/f1 /mydir/file1

101 -rwxr-xr-x

Inode Table Data Blocks


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Symbolic Links

Directory/mydir

f2 102

file2 103

Inode Table

102 rwxr-xr-x

103 link to /mydir/f2

Data Blocks

ln -s /mydir/f2 /mydir/file2


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Hard Links and Soft Links

There are two kinds of links available for your use:

hard links

soft, or symbolic, links

When you create a hard link, you are providing another name for the same file.Hard links let you link only files in the same file system. All the link names are onequal footing. It is incorrect to think of one file name as the real name, andanother as only a link.


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Hard Links and Soft Links

Soft links or symbolic links let you link both files and directories.

In addition, you may link both files and directories across different file systems.

A symbolic link is actually a distinct file that contains a pointer to another file ordirectory. This pointer is the pathname to the destination file or directory. Only theoriginal file name is the real name of the file or directory. Unlike a hard link, a softlink is actually only a link.


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Creating Links

To link a hard link, use the following command format:

ln

If you want to link files and directories across file systems, you can createsymbolic links.

To create a symbolic link, add an flag to the above command and specify fullpathnames of both files.


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Understanding Links

Each file has a unique identification, called an I-node number. The I-nodenumber refers to files data stored at a particular location - rather than to the filename.

A directory entry is a link between an I-node number and a file name. This linkenables you to link multiple file names to the same I-node number.

To display I-node number of files, use with the flag.


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Understanding Links

Hard links to a file carry the same I-node number. Since an I-node numberrepresents a file within a particular file system, hard links cannot exist between filesystems.

However, the soft link is a new file with its own, new I-node number.

Since the soft link refers to the original file by name, rather than by I-nodenumber, they work across file systems.


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Deleting Links

The rm (remove file) command does not always remove a file.

Assume that a file has several hard links (and therefore more than one file name).In this case, the command removes the link between the file I-node number

and that file name, but leaves the physical file intact.

The command physically removes a file only after it has removed the last linkbetween that file and its names.


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file determine file type

Syntax

file[options] [-m magic_file] [-f file_list] file

Common Options

-c check the magic file for errors in format

-f file_list file_list contains a list of files to examine

-h dont follow symbolic links (SVR4 only)

-L follow symbolic links (BSD only)

-m magic_file use magic_file as the magic file instead of /etc/magic

Examples

Below we list the output from the command "file filename" for some representative files.

/etc/passwd: ascii text

/usr/bin/ls: ELF 32-bit MSB executable SPARC Version 1

test.tar: USTAR tar archive

test.tar.Z: compressed data block compressed 16 bits


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ls -lcat

moretail

cpmvlnrm

Display file characteristics

Concatenate and display contents of files to screen

Format and display contents of files to screen

Display the end of files to screen

Copy files or directoriesMove or rename files or directories

Link file names together

Remove files or directories

File/Directory Manipulation Commands Summary


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Access to files is dependent on a user's identification and the permissions associated with a file. This module will show

how to

Permissions

ls (11, ls -l)chmodumaskchownchgrpsu

newgrp

Understand the read, write, and execute access to a file

Determine what access is granted on a file

Change the file access

Change default file access

Change the owner of a file

Change the group of a file

Switch your user identifier

Switch your group identifier

File Permissions and Access


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The UNIX system incorporates a three-tier structure to define who has access

to each file and directory:

user The owner of the filegroup A group that may have access to the file

other Everyone else

The ls -l command displays the owner and group who has access to the file.

$ ls -l-rw-r--r-- 1 user3 class 37 Jul 24 11:06 f1

-rwxr-xr-x 1 user3 class 37 Jul 24 11:08 f2drwxr-xr-x 2 user3 class 1024 Jul 24 12:03 memo

| |owner group

Who Has Access to a File?


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contents can be examined.

contents can be examined.

contents can be changed.

contents can be changed.

file can be used as a command.can become current working directory.

There are three types of access for each file and directory:

Read

files:

directories:

Write

files:

directories:

Execute

files:directories:

Types of Access


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Permissions are displayed with ls -l:

$ ls -l

- rw- r-- r-- 1 user3 class 37 Jul 24 11:06 f1- rwx r-x r-x 1 user3 class 37 Jul 24 11:08 f2d rwx r-x r-x 2 user3 class 1024 Jul 24 12:03 memo

user (owner)access

group access

other access

file owner

file group

Permissions


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Permissions

symbolic r w - r - - r - -

\ / \ / \ /

binary 110 100 100

\ / \ / \ /

Octal 6 4 4


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Default File Permissions

When you create a file or directory, the system automatically supplies adefault permission. The following is a typical file permission :

-rw-r--r--

This permission specifies that the owner has read and write permissions whilethe group and all others have only read permission.


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When you create a file or directory, the system automatically supplies adefault permission. The following is typical directory permission :

drwxr-xr-x

This permission specifies that the owner has read and write permissions whilethe group and all others have read and execute (search) permission.


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The default permission codes that your system provides relieve you from thetask of specifying them explicitly every time you create a file or directory.

If you want to create your own default permission codes, you must change

your user mask with the umaskcommand.


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Changing File Permissions

Use the chmod(change mode) command to set or change the permissions foryour files and directories. Please remember that whatever restrictions youimpose, the super-user can always override them.

There are two ways to specify the permissions forchmod: You can specify permissions with letters and symbols.

You can specify permissions with octal numbers.


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chmodmode_list file... Change permissions of file(s)

mode_list [who[operator]permission] [ ,... ]

who user, group, other or all

operator + (add), - (subtract), = (set equal to)permission read, write, execute

Original permissions: mode user group otherrw-r--r-- rw- r-- r--

$ chmod u+x,g+x,o+x file or $ chmod +x fileFinal permissions: mode user group other

rwxr-xr-x rwx r-x r-x

chmod Change Permissions of a File


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Changing Permissions Using Letters

The following is the format of the chmod command when using letters andsymbols:

chmod userclass-operation-permission filename

The userclass-operation-permission entry represents three codes thatspecify the user class code, operation, and permission code that you want toactivate. The filename entry is the name of the file or files whosepermissions you want to change.


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Use one or more of the following to define a user class:

u User (owner)

g Group

o All others (besides owner and group)

a All (user, group, and all others)


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Use one or more of the following to define an operation:

+ Add permission

- Remove permission

= Assign permission regardless of previous setting


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Use one or more of the following to define a permission:

r Read

s Set user or group ID

w Writex Execute


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Assume a file file1 that has -rw-r--r set of permissions.

Now, enter the chmodcommand with the flags go+w.

This command expands the permissions for both the group (g) and for others(o) by giving them write access (+w) to file1 in addition to the read accessthey already have.


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Setting Default Permissions

If you want to further restrict the permissions established by a program whenit creates a file or directory, you must specify a user mask with the umaskcommand.

The user mask is a value that determines the access permissions when a fileor directory is created.


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Setting Default Permissions

The umask command has following format:

umask octal-number

The octal-number is a 3-digit octal number that specifies the permissions tobe subtracted from default permissions (777 or 666).

Please note that through umask you actually specify permissions that arenotto be granted.


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

user group otherdefault permissions: rw- rw- rw-

set default permissions: rw- r-- ---

$ umask g=r,o=

umask Permission Mask


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SUID and SGID Files

It is often the case in Unix that an ordinary user must perform a task whichonly the root has the power to. Since it is not practical to give every user theroot password, setuid and setgid bits are used. A setuid program (or script)assumes the UID of the program owner when it is run (a setgid programassumes the GID of the program group when run). So a setuid root program(or script) has a special bit set such that it can be run by any user to performrootly tasks.

chmod u+s

-rwsr--r-- 1 smith user 1178 Feb 29 15:17 file

chmod g+sfile

-rwxr-sr-- 1 smith user 1178 Feb 29 15:17 file


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What's the sticky bit?

In the old days when machines did not have very much memory, the sticky bitwas used to force a program or file to remain in memory. Today, the sticky bitis largely used on publicly writable directories to ensure that users do notoverwrite each other's files.

When the sticky bit (t) is turned on for a directory users can have read and/or

write permissions for that directory, but they can only remove or rename filesthat they own.

Only root is permitted to turn the sticky bit on or off.

chmod +t/test

drwxrwxrwt 5 sys sys 543 May 29 09:41 tmp


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touch [-amc] file... update access and/or modification times of file

$ ll-rw-r--r-- 1 karenk users 25936 Aug 24 09:53 firstfile

-rw-r--r-- 1 karenk users 10245 Aug 24 09:53 secondfile$ touch newfile$ ll-rw-r--r-- 1 karenk users 25936 Aug 24 09:53 firstfile-rw-r--r-- 1 karenk users 0 Aug 25 10:02 newfile-rw-r--r-- 1 karenk users 10245 Aug 24 09:53 secondfile$ touch secondfile$ ll

-rw-r--r-- 1 karenk users 25936 Aug 24 09:53 firstfile-rw-r--r-- 1 karenk users 0 Aug 25 10:02 newfile-rw-r--r-- 1 karenk users 10245 Aug 25 10:05 secondfile$

touch Update Timestamp on File


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chown owner [:group] filename ...

$ iduid=303 (user3), gid=300 (class)$ cp f1 /tmp/user2/f1$ ls -l /tmp/user2/f1-rw-r----- 1 user3 class 3967 Jan 24 13:13 f1$ chown user2 /tmp/user2/f1$ ls -l /tmp/user2/f1

-rw-r----- 1 user2 class 3967 Jan 24 13:13 f1

Only the owner of a file (or root) can change the ownership of the file.

Changes owner of a file(s) and,

optionally, the group ID

chown Change File Ownership


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chgrp newgroup filename ...

$ iduid=303 (user3), gid=300 (class)$ ls -l f3-rw-r----- 1 user3 class 3967 Jan 24 13:13 f3$ chgrp class2 f3$ ls -l f3-rw-r----- 1 user3 class2 3967 Jan 24 13:13 f3

$ chown user2 f3$ ls -l f3-rw-r----- 1 user2 class2 3967 Jan 24 13:13 f3$

Changes group access to a file

Only the owner of a file (or root) can change the group

of the file.

The chgrp Command


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su [user_name]

$ ls -l /usr/local/bin/class_setup-rwxr-x--- 1 class_admin teacher 3967 Jan 24 13:13 class_setup$ id

uid=303 (user3), gid=300 (class)$ su class_adminPassword:$ iduid=400 (class_admin), gid=300 (class)$ /usr/local/bin/class_setup$

log out of su session$

CTRL + D

Change your user ID and group ID designation

su Switch User Id


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newgrp [group_name] Changes the group ID

$ ls -l /usr/local/bin/class_setup-rwxr-x--- 1 class_admin teacher 3967 Jan 24 13:13 class_setup$ iduid=303 (user3) gid=300 (class)$ newgrp teacher$ iduid=303 (user3) gid=33 (teacher)$ /usr/local/bin/class_setup$ newgrpreturn to login group status$ newgrp otherSorry$

The newgrp Command


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Access Control Lists

lsacl filename list the ACL for a filechacl ACL filename change the ACL for a file

$ lsacl funfile(user3.%,rw-)(%.class,r--)(%.%,r--) funfile$ chacl "user2.class=rw,%.%-r" funfile$ lsacl funfile(user2.class,rw-)(user3.%,rw-)(%.class,r--)(%.%,---) funfile$ chacl -d "user2.class" funfile$ ll funfile

rw-r----- 1 user3 class 3081 May 28 16:12 funfile$ lsacl funfile(user3.%,rw-)(%.class,r--)(%.%,---) funfile

S


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Permissions

chmodumask

chownchgrpsunewgrp

Define who has what access to a file

user, group, others

read, write, execute

Change the permissions of a file

Define the default permissions for new files

Change the owner of a file

Change the group of a file

Switch user ID

Switch group ID

File Permissions and Access Summary


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vi

Cursor Control Commands


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Cursor Control Commands

move up one line

line move one character to the left

line move one character to the right

move down one line

beginning of previous word

beginning of next word

end of current/next word

beginning of line

end of line

beginning of current/previous sentence

beginning of next sentence

beginning of current/previous paragraph

end of current paragraph

top line on screen

middle line on screen

bottom line on screen

Input modes


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Input modes

Command Mode Name Insertion Point

---------------------------------------------------------------------------------------

a append just after the current character

A append end of the current line

i insert just before the current character

I Insert beginning of the current line

o open new line below the current line

O open new line above the current line

Deletion commands


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Deletion commands

Command Function

x Delete only the current character

D Delete to the end of the line

db Delete from the current character to the beginning of the

current wordde Delete from the current character to the end of the current

word

dd Delete the current line

dw Delete from the current character to the beginning of the next

word

u undo the last change

Using the vi editor


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Using the vi editor

Start the vi program by entering following command:

This is a new file, so the system responds by putting your cursor at the top of ascreen.

Examples:

$ vi file1 [Return]

Using the vi editor


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Using the vi editor

Type the lowercase letter i to specify that you want to insert text to thenew file. The system does not display the i that you enter.

Enter following text, pressing Return key after each line:

You start the vi program by entering [Return]

the vi command optionally followed by the name [Return]

of a new or existing file.

[Escape]

Using the vi editor


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Using the vi editor

Press the Escape key to indicate that you have finished your currentwork.

Type a colon (:) to enter the Last Line mode. The cursor will beplaced on the last line of the screen, where you can enter thecommands recognized by the vi editor.

Enter lowercase letter next. This indicates to the system that youwant to write, or save, a copy of the new file in your current directory.

Using vi editor


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Using vi editor

Use dd command to delete current line.

Use dd command to delete lines beginning from the current line.

Use dw command to delete current word.

Use dw command to delete words beginning from the current word.

Using vi editor


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Using vi editor

Use ^ command to move to beginning of current line.

Use $ command to move to END of current line.

Use w command to move forward by word.

Use b command to move back by word.

Use e command to move to end of word.

Using vi editor


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Using vi editor

Use Ctrl-F command to move to next screen.

Use Ctrl-D command to move forward by half a screen.

Use Ctrl-B command to move to previous screen.

Position cursor to any opening bracket and press % key to see the matchingclosing bracket.

Press A command to add data to end of current line.

Using vi editor


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Using vi editor

Use yy command to copy current line.

Use yy command to copy lines from the current line.

Use p to paste the lines cut using the yy or the dd command. The linesare pasted AFTER the current line.

Use P to paste the lines cut using the yy or the dd command. The linesare pasted BEFORE the current line.

Using vi editor


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Using vi editor

Use . command to repeat the last add, update, delete or paste command.

Use x command to delete current character.

Use x command to delete characters beginning from the currentcharacter.

Use r command to replace current character with character.

Using vi editor


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Using vi editor

Use cw command to change current word with new word(s). Enter newwords and press ESC when done.

Use cw command to change words beginning with current wordwith new word(s). Enter new words and press ESC when done.

Use C command to replace remainder of the line. Enter new text andpress ESC when done.

Use G to move to end of file.

Using vi editor


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Using vi editor

Use :/string command to search the string.

Use n command to repeat the previous search.

Use :s/old_string/new_string command to substitute old_string withnew_string in the current line.

Use :,s/old_string/new_string command to substitute old_stringwith new_string in line m thru n.For first line set m to 1. For last line,

set n to $.

Using vi editor


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Using vi editor

Use :set nu command to see line numbers.

Use :set nonu command to remove line numbers.

Use :set ai to enable auto-indent feature.

Use :set noai to remove auto-indent feature.

Use :set sm (show match) to enable bracket-match feature.

Quitting the vi editor


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To save your work and quit:

Press the Escape key to indicate that you have finished your current work.

Type a colon (:) to enter the Last Line mode. Enter command .

This indicates to the system that you want to write, or save, a copy of the newfile in your current directory and quit the vi editor.



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To quit without saving your work :

Press the Escape key to indicate that you have finished your current work.

Type a colon (:) to enter the Last Line mode. Enter command .

This indicates to the system that you want quit the vi editor WITHOUT saving thechanges you made to the file SINCE THE LAST w command.

Searching for Text: /, n, N


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There is one here

and one more here

and yet one more

but not this

nor this One

next

previous

n

N

g

Configuring the vi session


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Configuring the vi session

To configure the vienvironment certain options can be set with the line editor command

:set during a viediting session.:set ignorecase ignore the case of a character in a search

:set list display tabs and carriage returns

:set nolist turn off list option

:set nonumber turn off line numbers

:set showmode display indication that insert mode is on

Alternatively, frequently used options can be set automatically when viis invoked, byuse of the .exrc file :set all display all option settings

The following is a sample .exrc file:

set number

set list

set ignorecase

vi Quick Reference


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Cursor Movement Commands:

(n) indicates a number, and is optional

(n)h left (n) space(s)

(n)j down (n) space(s)

(n)k up (n) space(s)

(n)l right (n) space(s)

(The arrow keys usually work also)

^F forward one screen

^B back one screen

^D down half screen

^U up half screen

H beginning of top line of screen

M beginning of middle line of screen

L beginning of last line of screen

G beginning of last line of file

0 (zero) beginning of line

$ end of line

(n)w forward (n) word(s)

(n)b back (n) word(s)

Inserting Text:

i insert text before the cursor

a append text after the cursor (does not

overwrite other text)

I insert text at the beginning of the line

A append text to the end of the line

r replace the character under the cursor

with the next character typedR Overwrite characters until the end of the

line (or until escape is pressed to changecommand)

o (alpha o) open new line after the current

line to type text

O (alpha O) open new line before the current lineto type text

vi Quick Reference


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Change Commands:

(n)cc changes (n) characters on line(s) until end of the line (or until escape is pressed)

cw changes characters of word until end of the word (or until escape is pressed)

(n)cw changes characters of the next (n) words

c$ changes text to the end of the line

C changes remaining text on the current line (until stopped by escape key)

~ changes the case of the current character

Jjoins the current line and the next line

u undo the last command just done on this line

. repeats last change

s substitutes text for current character

S substitutes text for current line

:s substitutes new word(s) for old

: s/old/new/g

& repeats last substitution (:s) command.

(n)yy yanks (n) lines to buffer

y(n)w yanks (n) words to buffer

p puts yanked or deleted text after cursor

P puts yanked or deleted text before cursor

vi Quick Reference


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File Manipulation:

:w (file) writes changes to file (default is current file)

:wq writes changes to current file and quits edit session

:w! (file) overwrites file (default is current file)

:q quits edit session w/no changes made

:q! quits edit session and discards changes

:n edits next file in argument list

:f (name) changes name of current file to (name)

:r (file) reads contents of file into current edit at the current cursor position (insert a file)

:!(command) shell escape

:r!(command) inserts result of shell command

vi editor - global replace


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g p

Use :s/old_string/new_string command to substitute old_string withnew_string in the current line.

Use :,s/old_string/new_string command to substitute old_stringwith new_string in line m thru n.For first line set m to 1. For last line,set n to $.

Use :g/ old_string/s//new_string command to replace old_string withnew_string in the file.

The grep Command


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The name of the grep command is an acronym forglobal regularexpression printer.

Basic form : grep

Grep can take input from file, standard input or a pipe ( output of anothercommand )

Options :-c : Prints the COUNT of number of matching lines

-v : Prints line that DO NOT match

-l : prints the names of files with matching pattern

-n : Prints line number with each matching output

e.g., grep -i error logfile

Matching filenames


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If the file names have a common pattern, the shell can match that pattern,generate a list of those names, and automatically pass them to thecommand as arguments.

The asterisk (*), sometimes referred to as a wildcard , matches any string

of characters.

Examples:

$ ls file *

Matching filenames


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If the file names have a common pattern, the shell can match that pattern,generate a list of those names, and automatically pass them to thecommand as arguments.

The asterisk (*), sometimes referred to as a wildcard , matches any string

of characters. For example, file* will match any filename starting withword file.

Matching filenames


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There is one exception to the general rules for pattern matching. When thefirst character of a file name is a period, you must match the periodexplicitly.

For example, displays the names of all files in the current directory

except those that begin with a period. The command displays all filenames, including those that begin with a period.

Matching filenames


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This restriction prevents the shell from automatically matching the relativedirectory names. These are . (for the current directory) and .. (for the parentdirectory).

In addition to the asterisk (*), shells provide other ways to match character

patterns. These are summarized in the next slide.

Matching filenames


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The filename pattern-matching characters are:

* - matches any string, including NULL

? - matches any single character

[] - matches any of the set characters[.-.] - matches any character within the

specified range

[!] - matches any character except those

in the set

New Topic


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Using Regular Expressions

Regular Expressions


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A regular expression specifies a set of strings to be matched. It containsordinary text characters and operator characters. Ordinary characters matchthe corresponding characters in the strings being compared. Operatorcharacters specify repetitions, choices, and other features.

Regular expressions fall into two groups:

Basic regular expressions

Extended regular expressions

Basic Regular Expressions


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Basic expressions are built by concatenating simpler basic regularexpressions.

Ordinary characters and operator characters together make up the set ofsimple basic regular expressions. You can concatenate any number or

combination of simple expressions to create a compound expression that willmatch any sequence of characters that corresponds to the concatenatedsimple expressions.

Basic Regular Expressions - Rules


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An ordinary character matches itself.

A period (dot) matches any single characterexcept the newline character.

An * (asterisk) matches any number of occurrences of the preceding simpleexpression, including none.



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The Bracket expression) matches a single instance of any one ofthe characters within the brackets. Ranges of characters can be abbreviatedby using a hyphen. For example, [0-9a-z] matches any single digit orlowercase letter.

Within brackets, all characters are ordinary characters except the hyphen(when used in a range abbreviation) and the circumflex (when used as thefirst character inside the brackets).


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The \char (Backslash) - except within a bracket expression, escapes the nextcharacter to permit matching on explicit instances of characters that areusually basic regular expression operators.

The exprexpr... (concatenation) - matches any string that matches all of the

concatenated expressions in sequence.


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Commonly Used Shells


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/usr/bin/sh/usr/bin/ksh/usr/old/bin/sh/usr/bin/csh/usr/bin/keysh/usr/bin/rksh/usr/bin/rsh/bin/bash

POSIX shell

Korn shell

Bourne shell

C Shell

A context-sensitive softkey shell

Restricted Korn shell

Restricted Bourne shell

Bash shell (GNU Bourne-Again Shell)

POSIX Shell Features


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A shell user interface with some advanced features: Command aliasing

File name completion

Command history mechanism

Command line recall and editing

Job control

Enhanced cd capabilities

Advanced programming capabilities

Aliasing


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alias [name[=string]]

$ alias dir=ls$ alias mroe=more$ alias mstat=/home/tricia/projects/micron/status$ alias laser="lp -dlaser"$ laser fileXrequest id is laser-234 (1 file)$ alias $ alias mroe mroe=more

File Name Completion


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$ more fra$ more frankenstein

.

.

.

$ more abc$ more abcdef =

1)abcdefXlmnop2)abcdefYlmnop

$ more abcdefThen type X or Y, then .

Associated file name will be completed

Return

ESCESC

ESCESC

ESCESC

ESC

Recalling Commands


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Uses the history mechanism. Must have the EDITORenvironment variable set.

EDITOR=viexport EDITOR

At $, press and use normal vi commands to scroll through previous commands. k scrolls backward through the command history.

j scrolls forward through the command history. nGtakes you to command number n.

Press to execute the command.

Return

Esc

Command Line Editing


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Provides the ability to modify text entered on current or previous command lines.

Press to enter command mode.

Recall desired command by either

Pressing until it appears

Typing the command number, then G Use vi commands to edit the line

Do not use the arrow keys

Enter to execute the modified command.

K

Return

Esc

The User Environment


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env

$ envHOME=/home/gerryPWD=/home/gerry/develop/basicsEDITOR=viTERM=70092...PATH=/usr/bin:/usr/contrib/bin:/usr/local/bin:\/home/gerry/bin

Your environment describes your session to the programs you run.

Setting Shell Variables


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A shell variable is a name that represents a value. The value associated with the name can be modified.

Some shell variables are defined during the login process.

A user can define new shell variables.

name=value

$ PATH=/usr/bin/X11:/usr/bin$ PS1=

Two Important Variables


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The PATH variable A list of directories where the shell will search for the commands you type

The TERMvariable

Describes your terminal type and screen size to the programs you run

$ env

...PATH=/usr/bin:/usr/contrib/bin:/usr/local/bin$ TERM=70092$$ tsetErase is BackspaceKill is Ctrl-U$

echo Displaying the shell Variable values


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There are a number of variables automatically set by the shell when it starts.

echo

$SHELL:Returns the name of the shell

$? : the exit status of the last command executed

$$ : the process number (PID) of this shell - useful for including in

filenames, to make them unique$! : the process id of the last command run in the background.

$- : the current options supplied to this invocation of the shell.

$* : a string containing all the arguments to the shell, starting at $1.

What Happens When a User Logs In?


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csh login scripts

/etc/csh.login

$HOME/.profile

$HOME/.kshrc

login: test12

password:

system login

script

local login

script

local

$

additional

login script

$HOME/.login

$HOME/.cshrc

POSIX login scripts

/etc/profile

The Shell Startup Files


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.profile

.kshrc

.profile

.profile

.kshrc

.profile

.login

.cshrc

Korn (/usr/bin/ksh)

Bourne (/usr/old/bin/sh)

POSIX (/usr/bin/sh)

Restricted (/usr/bin/rsh,/usr/bin/rksh)

C (/usr/bin/csh)

Shell Intrinsics versus UNIX Commands


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Shell intrinsics are built into the shell.

setwhileiffor

cdls

UNIX commands live in /usr/bin.

more

file

The system locates UNIX commands by using the PATHvariable.

Looking for Commands whereis


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$ whereis [-b|-m|-s] command Searches a list ofdirectories for a command

$ whereis ifif :$$ whereis lsls : /sbin/ls /usr/bin/ls /usr/share/man/man1.Z/ls.1$$ whereis cd

cd : /usr/bin/cd /usr/share/man/man1.Z/cd.1$$ whereis holdyourhorsesholdyourhorses :$

Commonly Used Shells


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/usr/bin/sh/usr/bin/ksh/usr/old/bin/sh/usr/bin/csh/usr/bin/keysh/usr/bin/rksh

/usr/bin/rsh

POSIX shellKorn shell

Bourne shell

C Shell

A context-sensitive softkey shell

Restricted Korn shell

Restricted Bourne shell


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Shell Substitution Capabilities


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There are three types of substitution in the shell: Variable substitution

Command substitution

Tilde substitution

Variable Substitution


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$name Directs the shell to perform variable substitution

$ echo $PATH/usr/bin:/usr/contrib/bin:/usr/local/bin

$ PATH=$PATH:$HOME:.$ echo $PATH/usr/bin:/usr/contrib/bin:/usr/local/bin:/home/user3:.$ echo $HOME/home/user3$ file_name=$HOME/file1$ more $file_name

Command Substitution


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$(command)

$ pwd/home/user2

$ curdir=banner $(ls)$ echo $curdir/home/user2$ cd /tmp$ pwd/tmp

$ cd $curdir$ pwd/home/user2


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Passing Variables to an Application


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env var

TERM=98550

STEP 1:

env var

TERM=98550

local variables

color=lavender

local variables

color=lavender

fork: program and

data spaces

are duplicated

local variables

parent sleeps $

env var

TERM=98550

env var

TERM=98550

local variables

color=lavender

STEP 2:are replaced with program and data

of requested program (/usr/bin/vi) and

program is executed. When program

(/usr/bin/sh) and the prompt is displayed.completes, control returns to the parent

program and local data spaceexec:

Monitoring Processes


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$ ps -fUID PID PPID C STIME TTY TIME COMMAND

user3 4702 1 1 08:46:40 ttyp4 0:00 -shuser3 4895 4702 18 09:55:10 ttyp4 0:00 ps -f

$ ksh

$ ps -fUID PID PPID C STIME TTY TIME COMMANDuser3 4702 1 0 08:46:40 ttyp4 0:00 -shuser3 4896 4702 1 09:57:20 ttyp4 0:00 kshuser3 4898 4896 18 09:57:26 ttyp4 0:00 ps -f

$ exec ps -fUID PID PPID C STIME TTY TIME COMMAND

user3 4702 1 0 08:46:40 ttyp4 0:00 -sh

user3 4896 4702 18 09:57:26 ttyp4 0:00 ps -f

$

Child Processes and the Environment


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$ export color=lavender$ ksh

$ ps -fUID PID PPID C STIME TTY TIME COMMAND

user3 4702 1 0 08:46:40 ttyp4 0:00 -shuser3 4896 4702 1 09:57:20 ttyp4 0:00 kshuser3 4898 4896 18 09:57:26 ttyp4 0:00 ps -f

$ echo $colorlavender$ color=red$ echo $colorred$ exit $ ps -f

UID PID PPID C STIME TTY TIME COMMAND

user3 4702 1 0 08:46:40 ttyp4 0:00 -shuser3 4895 4702 1 09:58:20 ttyp4 0:00 ps -f$ echo $colorlavender


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Introduction to Quoting


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Many characters have "special" meaning to the shell:white space

carriage return$#*< >Quoting removes (escapes) the special meaning of the special

characters.

Quoting Characters


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\'"

BackslashSingle Quotes

Double Quotes

Quoting \


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\ Removes the special meaning of the next character

$ echo the \\ escapes the next characterthe \ escapes the next character$ color=red\ white\ and\ blue$ echo the value of \$color is $colorthe value of $color is red white and blue$ echo one two \

> three fourone two three four

Quoting '


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' Removes the special meaning of all characters surrounded bythe single quotes

$ color='red white and blue'$ echo 'the value of \$color is $color'the value of \$color is $color$ echo 'the value of $color is' $colorthe value of $color is red white and blue$ echo 'this doesn't work'

>$ echo '**************'************

Ctrl + d

Quoting "


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" Removes the special meaning of all characters surrounded by thedouble quotes except \ , $, {variable name}, $(command),and "

$ color="red white and blue"$ echo "the value of \$color is $color"the value of $color is red white and blue$ cur_dir="$LOGNAME - your current directory is $(pwd)"$ echo $cur_dir

user3 - your current directory is /home/user3/tree$ echo "they're all here, \\, ', \" "they're all here, \, ', "

Quoting Summary


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Backslash

Single Quotes

Double Quotes

Escapes next character

Escapes all characters inside ' 'Escapes all characters inside " ", except \, $, {variable name},and $(command)


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Input and Output Redirection Introduction


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Shell

* ? [ ]

cmd >file

cmd 2>f.errcmd< file

Command execution

File name generation

Interpretive

programming language

Pipelines

I/O redirection

Environment settings

Variableassignment

Variablesubstitution

Commandsubstitution

export varname

env

variable=value

set

$varname

$(cmd)

stdin, stdout, and stderr


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Reset

BreakStop

f1 f2 f3 f4 f5 f6 f7 f8

Back

Space

ReturnCTRL

User

System

. / + -

7 8 9

4 5 6 ,

1 2 3

0 .

Menu

TabNext Select

Prev

Insert

line

Delete

line

Insert Delete

char char

|

\

}

]

{

[

=

+

_

-

"

'

:

;

Shift

Extend

char

?

/

>

.


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Any command that reads its input from stdin can have its input redirected to come from another file.

$ cat remind

Your mother's birthday is November 29$ mail user3 < remind$ mailFrom user3 Mon July 15 11:30 EDT 1993

Your mother's birthday is November 29

?d$

Output Redirection and >>


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Any command that produces output to stdout can have its output redirected to another file.

$ date > date.out $ ls >> ls.out$ date > who.log $ who >> who.log$ cat > cat.out $ ls >> who.loginput text here

Ctrl + d

Error Redirection 2> and 2>>


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Any command that produces error messages to stderr can have

those messages redirected to another file.

$ cp 2> cp.err $ cp 2>> cp.err

$

$ more cp.errUsage: cp [-f|-i] [-p] source_file target_file

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

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

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

What Is a Filter?


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Reads standard input andproduces standard output.

Filters the contents of the input stream or a file.

Sends results to screen, never modifies the input stream or file.

Processes the output of other commands when they are used in conjunction with output redirection.

Examples: cat, grep, sort,wc

wc Word Count


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Syntax:

wc [-lwc] [file...] Counts lines, words, and characters ina file

Examples:

$ wc funfile

116 529 3134 funfile$$ wc -l funfile116 funfile$$ ls > ls.out$$ wc -w ls.out

72 ls.out

sort Alphabetical or Numerical Sort


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sort [-ndutX] [-k field_no] [file...] Sorts lines

$ sort funfile

$ tail -1 /etc/passwduser3:xyzbkd:303:30:studentuser3:/home/user3:/usr/bin/sh1 2 3 4 5 6 7$ sort -nt: -k 3 < /etc/passwd

$ who > whoson

$ sort whoson $ sort -u -k 1,1 whoson

grep Pattern Matching


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grep [-cinv] [-e]pattern [-e pattern] [file...]grep [-cinv] -f patterns_list_file [file...]

$ grep user /etc/passwd

$ grep -v user /etc/passwd$ grep -in -e like -e love funfile

$ who > whoson$ vi whoson:1,$s/ .*//gZZ$ grep -f whoson /etc/passwd

Input and Output Redirection Summary


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cmd < filecmd > filecmd >> file

cmd 2 > file.errA filter

wcsortgrep

Redirects input to cmdfrom fileRedirects standard output from cmdto fileRedirects standard output from cmdand append to fileRedirects errors from cmdto file.err

A command that accepts stdin and generates stdout

Line, word, and character countSorts lines alphabetically or numerically

Searches for lines that contain a pattern


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Pipelines Introduction


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Shell

* ? [ ]

Command execution

File name generation

Interpretive

programming language

cmd >file

cmd 2>f.err

cmd< file

I/O redirection

Environment settings

Variableassignment

Variablesubstitution

Commandsubstitution

export varname

env

variable=value

set

$varname

$(cmd)

PipelinescmdA | cmdB

Why Use Pipelines


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$ who > temp_file

$ wc -l < temp_file

$ rm temp_file

who wc -l

The | Symbol


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cmd_A cmd_B*

$ ps -ef | more

cmd_C

generatesstderr

generates

stdout

generatesstdout

generatesstdout

generatesstderr

generatesstderr

acceptstdin

acceptstdin

$ ls | more$ ls | sort -r | more

*cmd_Bmust be a filter.

Pipelines versus Input and Output Redirection


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cmd_out >file cmd_out | cmd_inor

cmd_in who.out who | sortsort < who.out

Redirection in a Pipeline


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3 streams for each command:

-stdin-stdout-stderr

You can redirect streams that are not dedicated to the pipeline:

stdout stdin

cmd_A cmd_BAvailable forredirection:

stdinstderr

stdoutstderr

stdout stdin stdout stdin

cmd_A cmd_B cmd_Cstdinstderr

stderr stdoutstderr

Available forredirection:

$ grep user /etc/passwd | sort > sort.out

Some Filters


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Cuts out specified columns or fields and display to stdout

Translates characters

Passes output to a file and to stdout

Prints and format output to stdout

cut

tr

Tee

pr

The cut Command


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cut -clist [file...] Cuts columns or fieldscut -flist [-dchar][-s][file...] from files or stdin

$ date | cut -c1-3$ tail -1 /etc/passwduser3:mdhbmkdj:303:30:student user3:/home/user3:/usr/bin/sh1 2 3 4 5 6 7

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

$ cut -f1,6 -d: /etc/passwd | sort -r$ ps -ef | cut -c49- | sort -d

The tr Command


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tr [-s] [string1 [string2]] Translates characters

$ who | tr -s " "$$ date | cut -c1-3 | tr "[:lower:]" "[:upper:]"

The tee Command


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pr [-option] [file...] Formats stdin and produces stdout

$ pr -n3 funfile$ pr -n3 funfile | more$ ls | pr -3$ grep home /etc/passwd | pr -h "User Accounts"

Printing from a Pipeline


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cmd_out | cmd_incmd_out | cmd_in_out | cmd_in

Cuts out columns or fields to standard output

Sends input to standard output and a specified file

Prints formatter to the screen, commonly used with lp

Translates characters

Pipeline

cutteepr

tr


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The ps Command


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ps [-efl] Reports process status

$ psPID TTY TIME COMMAND

1324 ttyp2 0:00 sh1387 ttyp2 0:00 ps

$ ps -efUID PID PPID C STIME TTY TIME COMMANDroot 0 0 0 Jan 1 ? 0:20 swapperroot 1 0 0 Jun 23 ? 0:00 initroot 2 0 0 Jun 23 ? 0:16 vhand

root 3 0 0 Jun 23 ? 12:14 statdaemonuser3 1324 1 3 18:03:21 ttyp2 0:00 -shuser3 1390 1324 22 18:30:23 ttyp2 0:00 ps -ef

Background Processing


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command line > cmd.out &

$ grep user * > grep.out &

[1] 194

$ psPID TTY TIME COMMAND164 ttyp2 0:00 sh194 ttyp2 0:00 grep

195 ttyp2 0:00 ps

Putting Jobs in Background/Foreground


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jobs

fg [%number]fg [%string]bg [%number]bg [%string]

Displays jobs currently runningSuspends a job running in the foreground

stty susp ^ZBrings job number to the foreground or

any job whose command line begins with string.Transfers job number to the background or

any job whose command line begins with string.

Ctrl + z

The nohup Command


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nohup command line & Makes a command immune to hangup(logout) no hangup

$ nohup cat * > bigfile &[1] 972

$

login: user3Password:

$ ps -ef | grep catUID PID PPID COMMANDuser3 972 1 .... cat * > bigfile &

Ctrl + d Return

The nice Command


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nice [-N] command_line Runs a process at a lower priorityNis a number between 1 and 19.

$ nice -10 cc myprog.c -o myprog$ nice -5 sort * > sort.out &$

The kill Command


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kill [-s signal_name] PID [PID...]

$ cat /usr/share/man/cat1/* > bigfile1 &[1] 995

$ cat /usr/share/man/cat2/* > bigfile2 &[2] 996

$ kill 995[1] - Terminated cat /usr/share/man/cat1/* > bigfile1 &$ kill -s INT %2[2] + Interrupt cat /usr/share/man/cat2/* > bigfile2 &$ kill -s KILL 0

Sends a signal to specified

processes.


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Shell Programming Overview


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A shell program is a regular file containing UNIX system commands.

The file's permissions must be at least "read" and "execute."

To execute, type the name of the file at the shell prompt.

Data can be passed into a shell program through

environment variables

command line arguments

user input

Example Shell Program


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/usr/bin/sh

/usr/bin/date /usr/bin/ls

$

$ myprog

PID = 1324

PID = 1350

PID = 1361 PID = 1362

/usr/bin/sh

myprog

#

date

ls -F

Execution ofmyprog:

$ cat myprog#this is the program myprogdatels -F

Passing Data to a Shell Program


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$ color=lavender

$ cat color1echo You are now running program: color1echo the value of the variable color is: $color

$ chmod +x color1

$ color1You are now running program: color1the value of the variable color is:

$ export color

$ color1You are now running program: color1the value of the variable color is: lavender

Arguments to Shell Programs


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$ sh_program arg1 arg2 . . . argX$0 $1 $2 . . . $X

$ cat color3

echo You are now running program: $0echo The value of command line argument \#1 is: $1echo The value of command line argument \#2 is: $2

$ chmod +x color3

$ color3 red green

You are now running program: color3The value of command line argument #1 is: redThe value of command line argument #2 is: green

Arguments to Shell Programs (Continued)


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This shell program will install a program, specified as a command-line

argument to your bin directory:

$ cat my_installecho $0 will install $1 to your bin directorychmod +x $1mv $1 $HOME/binecho Installation of $1 is complete

$ chmod +x my_install

$ my_install color3

my_install will install color3 to your bin directoryInstallation of color3 is complete$

Some Special Shell Variables # and *


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# The number of command line arguments* The entire argument string

$ cat color4

echo There are $# command line argumentsecho They are $*echo The first command line argument is $1

$ chmod +x color4

$ color4 red green yellow blue

There are 4 command line argumentsThey are red green yellow blueThe first command line argument is red$

Some Special Shell Variables # and * (Continued)


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This enhanced example of the install program accepts multiple

command-line arguments:

$ cat > my_install2echo $0 will install $# files to your bin directoryecho The files to be installed are: $*chmod +x $*mv $* $HOME/binecho Installation is complete

$ chmod +x my_install2

$ my_install2 color1 color2my_install2 will install 2 files to your bin directoryThe files to be installed are: color1 color2Installation is complete

read variable [ variable ]

The read Command


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readvariable [ variable ... ]

$ cat color6echo This program prompts for user inputecho "Please enter your favorite two colors ->

fundamentals of unix - for freshers

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