Unix 3Days

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UNIX Shell Scripting

Y.V.S Prasad

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An Operating System is the Interface between theUser (software) and the Computer (hardware).

USER OS COMPUTER

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UNIX is a multiprogramming

Operating System. It permitsmultiple people to run multipleprograms.

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I/O management

data management

command execution

program development tools

portability

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time sharing

security

communications

accounting

graphics

Internet

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BASIC COMMANDS

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$ clear$ tput clear

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$ date Date, Time and TimeZone

$ date +%D Date in dd/mm/yy

$ date +%T Time in hh:mm:ss$ date +%Z Time Zone

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$ pwd

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$logname

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$tty

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$uname Name of UNIX

$uname r Current Release of UNIX

$uname n Host Name or Domain Name

$uname a Available Information of UNIX

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$passwd

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$ who

Col. 1: user names

Col. 2: device names of the terminals

Col. 3, 4, 5: date and time of logging in

Col 6: machine name$ who Hu u gives more detailed

info. and H with headers

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$cal calendar of the current month

$cal 03 calendar for the year 03 AD

$cal 03 2008 calendar for march 2008 AD

$cal 09 1752 11 days have been adjusted toaccommodate the concept of leap year.

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$echo computer Displays the word computer

$echo computer\c Displays the word computer

and the cursor continues OTHER FORMATS:

\a bell \t tab

\b backspace \\ back slash

\c no new line \0n ascii character (n is octal)

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$ printf my current shell is %s\n $SHELL

OTHER FORMATS:

%d decimal

%o octal

%f float

%s string%30s 30 characters space wide

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$ type date/usr/bin/date

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$ man date

$ man pwd

$ man man

MANUAL SECTIONS:

1 User Programs 5. Admin. File Formats

2 Kernel System Calls 6. Games

3 Library Functions 7. Macros4 Special Files 8. Admin. Commands

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$ stty a Displays all options

$ stty echo suppresses the echo of input$ stty echo restores the echo

$ stty echoe backspace does not remove

the character

$ stty echoe backspace removes the

character

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$ stty intr \^c control c is the interrupt key

$ stty eof \â control a is eof character

$ stty sane restores sanity to the terminal.COMBINING THE COMMANDS

$ date ; pwd

$ (date ; pwd)

$ (date ; pwd ) > newlistThe combined output of the two commands is sent to

the file newlist

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$ exit exits from the current shell

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$ cat > abc creating a file abc

.

.^d

$ cat abc displaying the contents of abc

$ cat v abc displays non-printable chars.

$ cat n abc numbering the lines

$ cat abc def > ghi merges two files abc, def

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$ cp abc abc1 copies abc into abc1

$ cp abc abc1 abc2 d1 the last argument must bea directory

$ cp -i abc abc1 interactive copying

$ cp R progs newprogs recursive copying

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$ rm abc removes a file abc

$ rm i abc interactive removal

$ rm r d1 recursive removal$ rm R d1 recursive removal

$ rm f abc forced removal

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$ mv abc abc1 renames a file abc to abc1

$ mv d1 d2 renames d1 directory to d2

$ mv a b c d1 moves a b c to d1 directory

$ mv i abc abc1 interactive renaming

$ mv R d1 d2 recursive renaming

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$ lp abc prints the file abc

$ lp dlaser abc default printer is laser

$ lp n3 m abc prints 3 copies and mails

the user a message

$ lp tChapter1 abc prints the title chapter1

$ lpstat gives the status of print jobs$ cancel request-id to cancel the request-id

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W hen you log on to the system, UNIX automatically

places us in a directory called the Home Directory.

To know your Home,

$ echo $HOME /home/prasad

~/foo here ~ identifies home

~prasad home of Prasad

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$ mkdir d1 create the directory d1

$ mkdir p d1/d2/d3 create the path d1/d2/d3

$ rmdir d1 removes d1 (d1 empty)$ rmdir p d1/d2/d3 removes tree (empty)

$ cd /home/kumar changes to kumar directory

$ cd .. moves to parent directory

$ cd moves to Home

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$ ls lists all in the ascending order

$ ls r lists in the descending order

$ ls a lists all files including . Files$ ls C width wise

$ ls F * (exe), / (dir), @ (links)

$ ls i along with i-node nos.

$ ls l long format

$ ls t sorts files (modi. Time)

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$ ls s lists file sizes in blocks

$ ls x multicolumn output$ ls R recursive listing

$ ls xR combined effect of x and R

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Every file or directory is associated with 3 types of

people. The User (owner of the file), the Group

(people who are close to the owner and whosepriority comes after the owner and perform a

common task) and Others (who are neither Users

nor Group).

The first column of $ ls l command would give the

permissions each category holds.

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Permission file directory

read ( r ) view, copy, compileview

write (w) modify add or del.

files

Execute (x) run to change

to the dir.

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Symbolic Method:

u user + give

g group - remove

o others = absolute give

a all r read

w write

x execute$ chmod u+x, g-r abc exec. for user, read for group

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Absolute Method:

4 read

2 write

1 execute0 no permission

$ chmod 777 abc read, write, exe. for all

$ umask to know the default perm.

$ umask 0222 suppress these permissionsto create default permissions

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W henever, a file is created, the filename is stored at

one place and the contents of the file are stored at a

different place on the storage media. Both are linked

together by a no. known as i-node no. or index nodeno.

W hen we copy a file, altogether a new file is created,

and the contents of the source file are copied to the

target file. This leads to repetition of same contentsand thus disk space wastage.

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Instead, we can create a link to that file, which is

actually nothing but copying the i-node no. of the

file to the new file rather than the contents. This is

called linking.

Linking is of two types.

1. Hard links

2. Soft links

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W hen we create a link within the same file system, it

is a hard link. A soft link spans across the file

systems.

Hard link will have the same i-node no. But soft link

will store the path of the source file and thus has a

different i-node no.

For directories, we can create soft links only. Softlinks are also known as symbolic links.

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In the case of hard link, even if the source file is

removed, the contents can be accessed through the

link.

In the case of soft link, if the source file is removed,

the soft link does not point to anything and thus the

contents can not be accessed.

$ln abc abc1 hard link of abc

$ ln s abc /var/abc1 soft link of abc

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vi stands for visual editor. This was developed by

Bill joy of BSD.

vi has 3 modes:

1. Append or Insert mode (data entry)

2. Command or Escape Mode (editing)

3. Last Line or Ex Mode (file operations)

$ vi new

By default, when we invoke vi, we are in mode 2.

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a append

i insert

l move the cursor right

h move the cursor left

k move the cursor up

j move the cursor down

x delete one characterdw delete one word

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dd deletes entire line

d$ deletes from current position to the end of line

d0 deletes from current position to the beg. of line

u undo

J join

G go to specific line no.

r replace one characterR replace till esc. is pressed

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o open mode after the line

O open mode before the line

yy yanking

pp pastingLast Line Mode Commands: W hen we press : from

command or escape mode, it is printed at the last

line. These commands are to be given at that colon.

:wq write and quit

:x write and quit

:q! quit without saving

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:s ///g substitute globally

: w write

:w! overwrite

:n next file:e file edit the file

:! execute a UNIX command

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Filters are commands that accept data normally from

the standard input, manipulate it and write results to

the standard output.

1. Simple Filters

2. Filters with Regular Expressions grep and sed

3. Advanced Filtering using awk

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Simple Filters include head, tail, tr, sort, uniq, cut,

paste, pr, comm, diff etc.

$ head emp.lst

Displays first 10 lines of the file, from the beginning.

$ head -15 emp.lst

Displays first 15 lines of the file, from the beginning.

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$ tail emp.st

Displays last 10 lines of the file, from the end.

$ tail -15 emp.lst

Displays last 15 lines of the file, from the end.$ tail +25 emp.lst

Displays lines starting with the line no.25 to the end.

$tail c -512 emp.stCopies last 512 bytes from emp.st

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$ tr a A

Translates each a with A in the input

$ tr ax by

Translates a with b and x with y in the input$ ls l | tr s

Squeezes multiple occurrences of spaces to one.

$tr d | < emp.lstDeletes the character | from the file emp.lst

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A file (data base file) can be sorted in the ascending

or descending order by sort.

$ sort emp.lst

Sorts in ASCII collating sequence white space first,numerals next, uppercase letters and finally lower

case letters.

$sort r emp.lstSorts in the reverse order

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$ sort n emp.lst

Sorts according to numeric order

$ sort u emp.lst

Sorts uniquely $ sort f emp.lst

Sorts in the insensitive case order

$

sort emp.lst o emp.lst1Sorts and stores the output in the file emp.lst1.

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$ sort c emp.lst

Checks if the file is sorted

$ sort m emp.lst emp.lst1

Merges two files emp.lst and emp.lst1$ sort t: emp.lst

Sorts by taking : as the delimiter among fields

$

sort k 2 emp.lstSorts on the second field

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$ sort k 3,3 -k 2,2 emp.lst

Sorts according to the third field and the secondary

key is second field.

$ sort k 5.7, 5.8 emp.lstSorts from 7th column of 5th field to the 8th column

of 5th field of emp.lst

Note: Sort considers tab as the default delimiter.However, as a user we should use : as the delimiter.

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$ uniq emp.lst (emp.lst must be sorted before)

Displays the lines uniquely

$ uniq u emp.lst

Displays the lines that are only unique$ uniq d emp.lst

Displays the lines that are having duplicates

$

uniq c emp.lstDisplays the frequency of occurrence of each line

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$ cut c1 emp.lst

Cuts the file vertically basing on character nos.

$cut c1-5,8 emp.lst

Displays 1 to 5 characters and the 8th character of

each line

$cut f1 emp.lst

Displays first field of the file

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$ cut f1,3 emp.lst

Displays first and third fields.

$ cut f1-3 emp.lstDisplays first, second and third fields

$ cut d: f1 emp.lst

Displays the first field by taking : as the

delimiter

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$ paste emp.lst emp.lst1 Joins two files emp.lst and emp.lst1 with the

tab

as the delimiter.$ paste d: emp.lst emp.lst1 Joins two files emp.lst and emp.lst1 with : as

the delimiter.$ paste s emp.lst W ould join all the lines two forma single line

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$ pr emp.lst

Prints file by adding suitable headers, footers and

formatted text. Adds five lines of margin at the

Top and five and the Bottom. The header shows

the date and time of lat modification of the file

along with the filename and page number.

$ pr -3 emp.lstPrints in 3 columns

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$ pr t emp.lst

Suppresses the header and footer

$pr d emp.lstDisplays in double line spacing

$ pr n emp.lst

Lines are numbered$ pr o 5 emp.lst

Left margin is 5

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$ pr h employee file emp.lst

Header is employee file.

$ pr +10 emp.lstPrints from page no. 10

$ pr l 45 emp.lst

Page length is set to 45

$ pr l45 emp.lst | lp

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$ diff emp.lst emp.lst1

Displays file differences. Suggests changes in

order that the two files are identical. Append a

Delete d

Change c$ diff e emp.lst emp.lst1

This produces a set of instructions only

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$ comm emp.lst emp.lst1

Both these files must be sorted. Shows 3 column

output. The first column contains the entries only

available in the first file, the second columncontains the entries only available to the second

file and the third column contains common

entries.$ comm -1 emp.lst emp.lst1

Suppresses first column in the output.

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$ comm -12 emp.lst emp.lst1

Suppresses first and second columns in the

output.

$ comm -123 emp.lst emp.lst1

Suppresses all columns in the output.

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GREP stands for Global Regular ExpressionPrinter.$ grep options pattern filename(s)

Options:-i ignore case -c count lines-v inverse role -l file names only

-n lines are numbered -f patterns in a file-e multiple patterns -E EREs

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Basic Regular Expressions (BRE):* Zero or more occurrences of the prev.

chr.

. A single Character

.* Any no. of characters or none

[abc] a or b or c

[a-z] any character between a to z[1-3] any digit between 1 to 3

[âbc] not a or not b or not c

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Basic Regular Expressions (BRE):[â-zA-Z] non-alphabetic character

abc exact character sequence abc

âbc abc not at the beginning of the line

abc$ abc not at the end of the line

âbc$ abc as the only word in line^$ lines containing nothing

\ nullify the meaning of meta characters

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Extended Regular Expressions (ERE):

ab+c a followed by one or more bs followed by c

ab?c a followed by optional b followed by c

abc or ac

a|b either a or b

(a|b)c either ac or bc

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Interval Regular Expressions (IRE):ab {2,4}c a followed by 2,3,4 bs followed by c

ab{2,}c a followed by at least 2bs followed by c

ab{2}ca with 2bs and c

Ex:

grep i abc emp.lst emp.lst1

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SED is a multipurpose tool which combines the work

of several filters.

Ex: sed options address action file(s) Addressing in sed is done in two ways:1. By one or two line nos.2. By specifying /pattern/

Line Addressing:$ sed 3q emp.lstDisplays first 3 lines of the file and quits from sed.

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$ sed n 1,3p emp.lstDisplays first 3 lines of the file. (p and n must be

used)$

sed n $p emp.lstDisplays the last line of the file

$ sed n 1,2p7,9p emp.lst

Displays selective groups of lines$ sed n 3,$!p emp.lstDo not print the lines from 3 to the end of the file.

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Using Multiple Instructions:

$ sed n e 1,2p e 7,9p emp.lst

Putting instructions in a file:

$ cat > patfile

1,2p

7,9p

^d

$ sed n f patfile emp.lst

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Context Addressing:

$ sed n /director/p emp.lst

Displays all the lines that contain director

$ sed n /director/, /manager/p emp.lstDisplays all the lines from director to manager

$ sed n 1, /director/p emp.lst

Line nos. and context addresses can be mixed$ sed n /â/p emp.lst

Displays all the lines that start with p (regular exp.)

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W riting selected lines to a file:

$ sed n /director/w dlist emp.lst

$ sed n /director/w dlist

/manager/w mlist emp.lstText Editing:

Inserting i

AppendingaChanging c

Deleting d

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$ sed 1i\

abc \

pqr emp.lst

$ sed 1a\

abc\

pqr emp.lst

$ sed 1c\

abc emp.lst

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$ sed /director/d emp.lst

SUBSTITUTION:

$ sed s/director/director1/g emp.lst

$ sed 1,5 s/director/director1/g emp.lst

MULTIPLE SUBSITUTIONS:

$ sed s/i/m/g

s/x/y/g emp.lst

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Named after its authors Aho, W einberger andKernighan, awk, until the advent of Perl, was the mostpowerful utility for text manipulation.

Syntax:awk options selection_crateria {action} file(s)

The selection_crateria filters the input and selects lines

for action component to act upon.

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Examples:

$awk /director/ { print } emplist

Checks for the pattern director and prints the entire

line(s). If selection_crateria is missing, the actionapplies to all the lines. If action is missing, the entireline is printed. Either of the two is optional (but notboth), but they must be enclosed within a pair of single

(not double) quotes.

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The following formats are equivalent:

$ awk /director/ emplist

$ awk /director/ {print} emplist$ awk /director/ {print $0} emplist

awk uses the special parameter, $0, to indicate the entire

line. It also, identifies the fields by $1, $2, $3,

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$ awk /director/ { print $1, $2} emplist

Unlike other Unix filters, awk uses a contiguoussequence of space and tabs as a single delimiter. If thedelimiter is other this, we have to explicitly express.

$ awk F| /director/ { print $1, $2} emplist

Line addressing is allowed in awk with the help of the

built-in variable NR. This prints the lines from 3 to 6.

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$ awk F| NR==3, NR==6 {print NR, $1, $2, $3}emplist

C-like printf statement is available in awk to format theoutput.

$awk F| /director/ { printf %3d %-20s %d\n, NR,$1,$2} emplist

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Every print or printf statement can be separately redirected with the > and | symbols. However, makesure that the filename or command that follows thesesymbols is enclosed within double quotes.

$ awk F| /director/ { print $1, $2 | sort } emplist

$ awk F| /director/ { print $1, $2 > abc } emplist

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Every expression in awk is interpreted either as a stringor a number, and awk makes the necessary conversionaccording to context. Awk allows the use of user-defined

variables but without declaring them. Variables are case

sensitive.Ex: x=sun; y=com

print x y gives suncom

x=5; y=6;

print x+y gives 11

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Logical Operators:

|| (or), && (and), ! (not)

$ awk $3==director || $3==chairman {print } emplist

Regular Expression Operators:~ (match), !~ (no match)

$ awk $3 ~ /â { print } emplist

Number Comparison: >, >=, <, <=, ==, !=

Arithmetic Operators: +, -, *, /, %

$ awk $3 > 2000 { printf %d\n, $2*0.5 } emplist

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Built-in Variables:

NR cumulative no. of lines read

FS input field separator

OFS output field separatorNF no. of fields

FILENAME current input file

ARGC no. of command line arguments ARGV list of arguments

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Awk patterns can be put in a file and we can awk tolook for the pattern in that file and execute on theinput file. Here the file is pattern.awk.

$

awk f pattern.awk emplistBEGIN & END Sections: BEGIN performs actionsbefore processing each line and END performsactions after the last line of the file. BEGIN {action}

and END {action} is the syntax.$ awk BEGIN {print welcome} /director/ {print} END

{print Bye} emplist

awk reads standard input when filename is omitted.

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Arrays:

An array is considered declared the moment it is used

Array elements are initialized to zero or empty string

unlessinitialized explicitly. Arrays expand automatically. The

index

can be anything even a string

Ex:$ awk BEGIN { print REPORT } /director/ {tot[1]=tot[1]+$6 } END {print

$tot[1] } emplist

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Associative Arrays: Awk does not treat array indexes as integers, the arraysare associative, where the information is held as key-

value pairs. The index is the key that is saved internally

as a string. W hen we set an array element usingmon[1]=mon, awk converts the number 1 to a string.There is no specified order in which the array elementsare stored.

$ nawk BEGIN {print HOME = ENVIRON [HOME]}

emp.lst

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Functions:int (x) returns integer value of xsqrt (x) returns square root of xlength returns the length of a complete line

length (x) returns the length of xsubstr (string,m,n) starting from m, n characters asa string

index (s1,s2) returns the position of s2 in s1split(string,array,ch) splits the string into an array

using ch asthe delimiter

system (cmd) executes operating system commandsand returns exit status

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CONTROL FLO W :if (condition) { statements }if (condition ) { statements } else {statements}for (k=1;k<=10;k++){

statements}for ( k in array){

statements

} while (condition){

statements}

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FIND is a one of the power tools of UNIX. It recursively examines a directory tree to look for files matchingsome criteria and then takes some action on the selectedfiles.

Ex: find path_list selection_criteria action

Path List: Path List can be one or more sub-directoriesseparated by white space.

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SELECTION_CRITERIA:-inum n Having inode no. n-type x where x is f (ordinary file),

d (directory), l (sym. Link)-perm nnn matches permissions nnn-links n having n links-user username owned by username-group gname owned by group name-size +x[c] if size is > x blocks (c for char)

-mtime x if modified in < x days

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SELECTION_CRITERIA:-newer fname if modified after fname-atime +x if accessed in more than x days-name fname file name

-prune dont descend directory if matched

ACTION:-print prints on the output

-ls executes ls lids command-exec cmd executes UNIX command cmdfollowed by {}\;

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xargs is a command of Unix and most Unix-like operatingsystems. It is useful when one wants to pass a largenumber of arguments to a command. Arbitrarily long listsof parameters can't be passed to a command,so xargs will

break the list of arguments into sublists small enough tobe acceptable.For example, commands like:

rm /path/*rm ̀ find /path -type f`

will fail with an error message of "Argument list too long"if there are too many files in /path.

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find /path -type f -print0 | xargs -0 rmIn this example, find feeds the input of xargs with a longlist of file names. xargs then splits this list into sublistsand calls rm once for every sublist. This is more efficientthan this functionally equivalent version:find /path -type f -exec rm '{}' \;

which calls rm once for every single file. Note howeverthat with modern versions of find , the following variantdoes the same thing as the xargs version:

find /path -type f -exec rm '{}' +

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zipping the files abc, pqr and lmn:$ zip final.zip abc pqr lmn

recursive zipping:$ zip r final.zip d1 (d1 is a directory)unzipping the zipped files:$

unzip final.zip viewing the zipped files:$ unzip v final.zip

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Zipping a file:$ gzip abc.txt lmn.txtFiles abc.txt.gz and lmn.txt.gz are createdHow much zipping is done?

$ gzip l abc.txt.gz lmn.txt.gzUnzipping a file:$ gzip d abc.txt.gz lmn.txt.gz$ gunzip abc.txt.gz lmn.txt.gz

Recursive zipping:$ gzip r d1 (d1 is a directory)Unzipping recursively:$ gzip dr d1 or $ gunzip r d1

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A process is the instance of a running program. A process is said to be born when the programstarts execution and remains alive as long as theprogram is active. After execution is complete,

the process is said to die. Each process isuniquely identified by a unique integer calledthe process-id or PID.

$ psDisplays PID, TTY, TIME (cumulative processortime that has been consumed since the processstarted) and the CMD (process name)

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$ ps f

Displays full listing$ ps e or $ ps A All processes including user and system processes$ ps u user

Displaying the processes of a User$ ps aProcesses of all users excluding processes notassociated with terminal.$ ps lLong listing showing memory related information$ ps t termDisplays processes running on the terminal

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A process can be run in the background. This isachieved by placing an & at end of thecommand.$ sort emp.lst o emp.lst &

W hen a user logs out, the Shell is killed and allthe background processes are also killed. W ecan avoid this by using nohup command.

$ nohup sort emp.lst o emp.lst &This sends the output to nohup.out file. Even if the parent is killed, the background processruns and the result is sent to the file, nohup.out

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Processes in UNIX are usually executed withequal priority. The priority levels can be alteredusing nice command. A higher nice value alower priority.

Nice priorities normally range from 0 to 39.

$ nice n 5 wc l uxmanual &Nice value is increased by 5 units.

$ ps o nice shows the nice value.

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A Signal is used to communicate the occurrenceof an event to a process. Each Signal isidentified by a number and is designed toperform a specific function. Signals can begenerated from the keyboard or by the killcommand. Signals are represented by theirsymbolic names having the SIG prefix.If you want to terminate a program, younormally press the interrupt key. This sends theprocess the SIGINT signal (no. 2). The defaultaction of this signal is to kill the process. A process may also ignore a signal or executesome user-defined code written to handle thatsignal.

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There are two signals that a process cannotignore or run user-defined code to handle. They are SIGKILL and SIGSTOP.

kill command sends a signal, usually with theintention of killing one or more processes.

$ kill 105$ kill s KILL 105 (or) $ kill -9 105

$ kill l will display the list of signal names and theirnos.

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A job is the name given to a group of process.Process activity is related to kernel whereas the

job activity is related to shell.$ wc c /

Say that this command is taking too long, then we can suspend this command by pressingcontrol-z.[1] + stopped wc c /$ bgforces the command to run in the background$ jobs

will show the list of background jobs

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AT tells UNIX when to execute a set of commands.$ at 14:08.control-d$ at l

gives the list of at jobs$ at rto remove the list of jobs from the queue.

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Other formats of AT are:

$ at 15$

at 5pm$ at 3:06pm$ at noon$ at now + 1 year

$ 3:08pm + 1 day $ 15:08 December 18, 2008$ at 9am tomorrow

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BATCH commands are executed as soon as thesystem load permits.

$batch..

..control-d

job 10411856731.b at Sun Dec 29 13:14:33 2009

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CRON is a system process (daemon) thatexecutes programs at regular intervals. It mostly dormant, but every minute, it wakes up andlooks into a control file called the crontab file.Creating a crontab file:

create a file cron.txt with the following 6 fields.$ vi cron.txt00-10 17 * 3,6,9 5 wc c abcfield 1: 00-59 minutes field 4: month

field 2: 1-24 hours field 5: Friday field 3: 1-31 day field 6: command$ crontab cron.txt

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$ crontab ldisplay the contents of crontab file$ crontab rremoves the contents of crontab file$ time sort emp.lst o emp.lstdisplays 3 timesreal: time elapsed from the invocation of the

command until its termination.user: time spent by the program in executing

itself.sys: time spent by the kernel

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TRAP traps the signals and executes thecommands. It is normally put at the beginningof the shell script.$ trap command_list signal_list

W hen a script is sent any of the signals insignal_list, trap executes the commands in thecommand_list. The signal list can contain the

integer values or names (without the SIGprefix) of one or more signals the ones which you use with the kill command. Instead of using 2 15 to represent the signal list, you canalso use INT TERM etc.

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$ trap Pressed control c or control z ; exit INT TERM while truedo

sleep 60done You may ignore the signal. This can be achieved by,$ trap 1 2 15That is you should put a null command list.$ trap To reset the signal to their defaults

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W hat is a Shell? A Shell is the user interface to the

Unix Operating System (Kernel). Ittakes the input from the user andinterprets to the Operating System

and conveys the output from theOperating System back to the user.

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SHELL PROGRAMMING

User Shell Kernel

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SHELL PROGRAMMINGUnix is one of the first operatingsystems to make the user interface

independent of the operatingsystem. Even though there is only one Kernel running on the system,there can be several Shells in action one for each user who is loggedin.

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SHELL PROGRAMMINGPopular Shells:

1. Bourne Shell (sh)

2. Korn Shell (ksh)

3. C Shell (csh)

4. Bourne Again Shell (bash)

5. Tenex C Shell (tcsh)

6. Zee Shell (zsh)

Documents

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