1. $ LOGNAME : It displays the current user information
  2. $PWD : present working directory
  3. $DATE : It displays the system date & time
  4. 4. $clear           : To clear the screen
  5. 5. $cal : it current month and year
  6. $cal 2000           : Displays the 2000 year calendar
  7. $cal 8 2006 : displays the 8th month of 2006
  8. $exit or logout : exit from current user account
  9. $ who : displays the all user in who are currently working on server
  10. $finger : displays the all user who are currently working on server with more information
  11. Who am I : displays current user information
  12. Which or where : displays the location of the given command

Syn: $which pwd

  1. Cat : is use to create new files or to open exiting files or to append data to the exiting files

Create: cat >filename



Redirect: cat file1 file2 file3 >file4——–àredirect output

Append: cat >>filename——–à single file        $cat file1 file2 file3 >>EMP——àmulti files



Open file: cat <filename—–àopen single file   $cat file1, file2, file3———-àto open multi files

Cat >.filename———for hidden files

  1. Touch : It is used to create an empty file i.e. 0 byte file

SYN: $ touch filename

$ touch file1 file2 file3———à create multiple files

  1. rm : deleting files or directories


rm filename—————-àdeleting single file

rm -i filename————–àdeleting files with confirmation

rm file1 file2—————-àdeleting multiple files

rmdir dirname————–àdeleting the directory but the directory must be empty

rm  -r dirname————-àdeleting directory recursively (i.e. with tree str)

rm –ri dirname————-àremove directory with confirmation

rm *   ———————à it delets all files

rm  -I *——————–àdelets all files with confirmation

rm t* ———————àit delets whose file name starts with ‘t’

  1. mkdir : creating directories

Syn: $mkdir dirname

Sys: $Mkdir .dirname————àhidden directory

  1. Cd : change directory

Sys: $cd abc

$pwd——/home/madhav/abc using above cmd we can come out from abc now we at //home/madhav

cd..—————————àto come out from current directory

cd../..————————àparent directory

cd/—————————àit changes to root directory

cd ~————————-àit changes to home directory



  1. cp :copy source file to target file


Cp emp1 emp2———————-àemp1 tp 2 coping

Cp –I m1 m2————————-àoverwrite confirmation? Y

Cp –R source directory to target directory——-cp –R abc xyz

  1. mv : it is used to rename or move file

Ex: mv exiting filename new filename

Mv emp .emp———————-àto hide

Mv .emp emp——————–àto unhide

20.ls                       : display, list of all files & directories in a current directory

21.ls|more             : display, list of all files & directories page by page

  1. ls –a : display, list of all files & directories including hidden files and dirctories also in current directory
  2. ls –r : display list of all files & directories revers order in a current directory
  3. Ls –R : display list of all files & directories recursively in a current directory
  4. 25. Ls –t : display list of all files & directories according to date of creation in a current directory
  5. Ls –F : display all list of files & directories, link files, .exe files in a current directory
  6. Ls-x : display all list of files & directories according to width wise in a current directory
  7. 28. Ls-L : display all list of files & directories in a current directory in a long list i.e. 9 fields

1) File types

[1) — For regular file ii) d—for dir file III) L—for link file IV) b—for block of filesV) c— for char files] [here IV, V is device files]

2) File permissions 3) no. of links 4) owner name 5) group name 6) file size in bytes 7) Date 8) time 9) filename


  1. cmp : it compares two files char by char

Sys: cmp file1 file2

Ex: a1: Hello Good Morning

a2: Hello Good Evening

If two lines are same then return nothing

If two files are are different then it displays line number with character position

  1. comm. : It display common lines b/w 2 files

Syn: Comm File1 file2

  1. 32. diff : it display different lines b/w 2 files
  2. 33. pg : it display the file contents page by page

Syn: $Pg filename

  1. more : it also display the file contents page by page

Syn: $more filename

  1. head :it display the 1st n lines from the file

Sys: $ head –n filename

  1. 35. tail : it display the last n lines from file

Syn: tail –n filename

Tail +n filename—-àit indicates nth line to end of the line

Ex: tail +30 file (in this file total no of records is 100) it displays the records from 30th to 100

  1. 36. wc : it counts the no of lines, words, chars in a given file.

Syn: $wc filename

  1. i) wc –l filename——————àit gives the no of lines in a given file
  2. ii) wc –w filename—————àit gives the no of words in a given file

III) wc –c filename—————à it gives no. of char in file

  1. iv) wc -lw filename————–à it gives the no of lines and character in a given file


  2. i) ‘*’——–àit matches ‘0’ or more chars
  3. ii) ‘?’ ——-àit matches any single chars

iii) [    ] —àit matches any single chars in the given list

  1. iv) ‘–‘——àit matches any single char in the given range
  • ls t*—————àit list the files starts with ‘t’


  • ls *s  ————-àit list the files that ends with ‘S’



  • ls b*k————–àit list the files starts with ‘b’ and ends with ‘k’


  • ls a?————–àit list the 2 characters filename 1st later fallowed by ‘a’ and second letter is any one character



  • ls[bknt]———–àit list the files starts with ‘b’ or ‘k’ or ‘n’ or ‘t’


  • ls [abcdefgh] or ls[a-h]*–àlist the files, first char b/w ‘a’ to ‘h’



  • ls [b-k][p-t][d-n]*———à it list the files the 1st character ‘b’ to ‘k’ 2nd char ‘p’ to ‘t’ 3rd char ‘d’ to ‘n’ after that any no of characters
  1. grep : [globally search a regular expression and print it]

Is used for to search a string or regular expression in a given file(s)

  1. I) Eg: $ grep madhav sample

O/p: 2nd line

5th line

7th line

  1.  ii) Eg: $grep madhav a1, a2, a3:




iii) $ grep techno *——àit searches for techno in current dir files (all files)

  1. iv) $grep techno soft sample—–àit searches for more than one word

We kept it in “   “

  1.  v) $grep “techno soft” sample

grep cmd options

$ grep –i techno sample———————–àignore case sensitive

$ grep –c techno sample———————–àcount no of lines

$grep –n techno sample———————–àprint along with the line numbers

$grep –l techno *——————————àlist only file names

$grep –v “techno soft” sample—————ànot matches print the lines

$grep –ci techno sample———————-àIgnore case sensitive found no of lines

$grep “techno *” sample———————àpattern

Regular expression: any string contains wildcard charctor knows as regular expression or pattern

            These patterns are of 3 types:

Charctor pattern: the default pattern  is char pattern only

  1. i) $grep “techno *” sample
  2. ii) $grep “b [aeiou] ll” sample

iii) $grep “b..d” sample—ài.e. or matches any single charctor

Word pattern :/<    />

/< ——-àstart of the word

/>——àend of the word

Grep “/<techno/>” sample ————ào/p: techno

Grep “/<techno” sample—————-ào/p: techno soft

—————–ào/p: techno 123

Grep “techno/>” sample              —-ào/p: hellotechno, abctechno

Grep “/< [0-9][0-9][0-9][0-9]/>” sample————–àit display 4 digits       (i.e.1234, 4567)


Line pattern: ^———-starts of the file

$———-ends of the file

Ex: grep “^d” sample—————àit display the line starts with‘d’

Grep “^the” sample—————–àit list the lines start with ‘the’

Grep “^/<the/>” simple ———-àsample the line exactly start with ‘the’

Grep “t$” simple——————-àlist the line ends with‘t’ or last char is‘t’

Grep “[0-9] $” sample————à display the line ends with 0 to 9 digit

Grep “^ [bkt]” sample————àlist the line starting with ‘b’ or ‘k ‘or’t’

Grep “^ [^bkt]” sample———-àlist the line which is not start with ‘b’ or ‘k’ or‘t’

Grep “”^UNIX$” sample ———àdisplay the line having only word ‘Unix’

Grep “^…. $”———————-àlist the line which contains ‘4’ characters

(.)———————————-àrepresent single charctor

Grep “^.”————————àSample it list all lines

Grep “/.” Sample: ————–àit lists the line start with (.)

We use \ to search *, $, ^ as a charctor——-à i.e.\*,|^,\$

Grep “^$” sample————–à it list empty lines

Grep –c “^$” sample———-àcounts no of empty lines in a file

Grep –v “^$” sample———-àprint not matches (i.e. not empty) lines

Grep –v “^$”sample >temp

Mv temp sample——————-àhere both are delete empty files

  1. fgrep : it is used for search multiple strings but it doesn’t allow to search regular expression

$grep “hello


>UNIX”sample———-àit searches for hello or techno str UNIX

  1. 40. egrep : it is combination of grep and fgrep

$egrep “hello


>UNIX”sample       $egrep “^$” sample

  1. Sed : to replace a string

$ sed “s/existing string/new string/g” filename–àsed is used to find and replace and grep is for find print

  1. i) $sed “s/Unix/Linux/gi “madhav: ————-à ‘i ‘for case sensitive
  2. ii) $sed “s/^Unix/Linux/gi”———————-à whatever lines starting with UNIX are replaced by Linux

iii) $sed “s/^$/I like Unix/g I” sample——–àempty string are filled with ‘I like UNIX’’

  1. iv) $Sed “s/Unix//g I” sample—————–àit search UNIX if found replace with ‘nothing’ (empty)
  2. tr : to translate a charctor
  3. i) tr “a” “p” <s——————–à it read data from sample and ‘a’ is replaced by ‘p’
  4. ii) tr “aeiou” “AEIOU”<sample—-àreplace char by char

iii) tr “,” “lt” <emp—————-àwhenever “,” is there replace with tab space

  1. iv) tr “[a-z]” “[A-Z] <Siva——–à converts hole file into uppercase

43) Cut         : it is used for to retrieve required fields and characters from a given file

Ex: madhav is good boy–à18 chars

Cut –f 2-5 madhav—ào/p: adha

Cut –c 1-10 madhav

Cut –c 5-10, 15-20 madhav——-àfor every line 5-10, 15-20 characters

44) Paste     : is used for to join two or more files horizontally by using delimiter

Cat >states                                          cat >cities            paste –d “:”states cities>tr filename

AP                                                      Hyderabad               AP: Hyderabad

Tamilnadu                                            madras                   Tamilnadu: madras

Karnataka                                            Bangalore                Karnataka: Bangalore

Kerala                                                 Trivandrum

Maharashtra                                         Bombay

45) Sort        : it is used for to sort the file content. By default it sorts file contents based on ASCII values-àdefault is ascending

Sort sample

  1. i) sort –r sample——àdisplays descending order
  2. ii) sort –u sample—–àit displays unique lines in the given file

iii) sort –n file—-à’N” numeric comparisons

  1. iv) sort –nur file
  2. v) sort sample >temp

$mv temp sample

Sorting the data field by field

+pos–àstarting field

-Pos–àending field (optional)

  1. i) Sort –f +pas1 –pas2 filename
  2. ii) Sort –f +1 -3 filename—–àstarting from end before 3

iii) Sort –fn +2 -3 file ——àit gives only numbers

46) Uniq       : it displays unique lines in the given file but the file contents should be in sort order

Ex:file1         i) $ uniq file                  ii) $uniq –u filename–àit eliminates duplicates Aaaaaa

Aaaaaa         Aaaaaa                             ccccc

Aaaaaa         cccccccc                            ddddd

Ccccccc         dddddd                             Ppppp

Ddddd           hhhhhh                             ttttttt

Hhhhh           pppppp

Hhhhh           ttttttttt



iii) $ Uniq –d filename—-displays only duplicated lines   IV) uniq –c filename—–àit counts how many times lines duplicated



  1. V) $ uniq –u file >temp

$ mv temp filename

Delete duplicated lines from file                         Ddddd—–1




47)piping(|)     : it is used for to combine 2 or more cmds |take left side o/p to right side cmd as i/p

  1. i) $who |wc –l———àcount total no of lines (files) in current directory
  2. ii) $ ls|wc –l————àdisplays total no of subdirectories in the current directory

iii) ls –l |grep “^d”—-àdisplays total no of subdirectories who stats with line no‘d’

iV) $head -30 sample|tail +20 sample——àdisplay the the lines from 20 to 30 from given file

  1. v) $ grep UNIX stud | cut –f 2, 3|sort filename —–àdisplay UNIX students names & ph no in ascending order

48) $tee            : it is used to for to write data to the file as well as to the screen

$grep UNIX stud | cut –f 2, 3 |sort |tee file1

49) Shell scripting:

It is group of UNIX commands and shell keywords

The main concept of shell scripting is to handle text files

  1. I) Boune shell—-àsteave Bourne —–à$——–sh— (sh as interpreter)
  2. ii) Bash shell (borne again shell) —same as above–àadvanced version of Bourne is BASH (Linux default shell)

iii) Korn shell——David korn—-$———-ksh (interpreter) —-àused as AIX default shell

Mostly used shell is korn shell it supports re usability, all shell designed on bourn shell

50) $ksh            : shift to korn shell

51) $echo $0              : it displays current child shell name

52) $alias                    : it lists all alias names

53) Unalias alias names: to delete alias names

54) $ history                 : it displays the previously executed commands

55) Echo                          : it display the string on screen (monitor)

File permissions:(xxx/xxx/xxx)

User/owner—permissions     (first part)

Group permissions                    (second part)

Other permissions                    (third part)

+— (add permissions to u/g/o but it does not delete exiting permission)

— (deny permissions)

=—- (assign permissions (add permissions to u/g/o but it  delete exiting permission))

rw-/rw-/r– ———àDefault permissions for regular files

rwx/rwx/r-x———àdefault permission for directories

56) chmod              : it is used for to change file permissions

Syn: $chmod who/ [+/-/=]/

  1. i) ls –l filename——-àrw- rw- r—
  2. ii) chmod g+x filename—–àrw- rwx r—

iii) chmod u+x, g-w filename——àrwx r-x r—

iV) chmod g=w filename—–àrwx –w- r—

Octal code




$chmod 756 filename——-àrwx r-x rw-

$chmod 642 filename—-àrw- r–  -w-

57) chown        : to change owner name of the file

#chown owner name filename

58) chgrep    : to change group name of the file

# chgrp group name filename

58) $write    : it is user for to with the users but the user should be logged into the server

$write techno2                   ii) $mesg n–àdeny the msg

Hello                       iii) mesg y-àto allow msges


59) awk/nawk file            : scan for patterns in a file and process the results

60) cat                            : concatenate (list) or file

61) chsh (paawd –e/-s) userlogin_shell: change the user login shell

62) df                              : report the summary of disk blocks and nodes free and in use

  1.  i) df –k—àit displays the disk space in bytes
  2. ii) df –h—àit displays disk space in kilo bytes

iii) df –g—àit displays the disk space in giga bytes

63)du  :it displays the directory wise disk usage in form of blocks each block size is 512 bytes

64)g zip                  :to create a zip file

Ex $gzip filename—-ào/p: filename.gz

65) gunzip             : to unzip the files

Ex: gunzip filename.gz

  1. compress : it also used for to zip the file—àit used to save with .z format

67) Uncompress     : same as above

Gzip saves more memory than compress

68) zcat                 : it used to displays zip file contents in readable format

$zcat sample.gz



$zcat sample.z

69) To kill foreground job cntl+c or cntl+z

$ sleep 500


$ sleep 100&

70) ps or $ ps –f   : it displays current user account running process list (show status of active process)

71) $ps –a: it displays all user accounts running process list

72) Kill                           : it kill background process

Ex: kill PID

73) telnet           : to connect to remote server

74) ftp: file transfer protocol —–àtransfer files from one server to another

$ ftp ipaddress

Login: ——-

Password: ——

Ftp>ls  (server)


Ftp>get filename (to download a file)

Ftp>mget file1 file2—– (to download multi files)

Ftp>put filename (to upload a file)

Ftp>mput file1 file2—– (to upload multi files)

75)Ftp: to transfer files from one server user account to another server user account

$su root –àto switch to admin

76) Wall                  : it is used for to sent broadcast message to all users who are currently working on server


Happy new-year


77)mail         :it is used for to send the mail, if user is not logged in then also we can send mail

  1. i) $ mail techno1

Cntl+d every user contains mailbox

at a time we can send msg to multiple users

2) $mail techno1 techno2 techno 3

Sub: from techno


iii) $ mail techno<stud

stud send content as a mail to techno3

mail is the cmd to read mails in the mailbox


1>first mail

2>second mail reading

&2 it quickly opens second mail

&q–àquit from mail box

&w to save mail contents to a file

&pàprint mail contents


&d-àdelete mails

78)$mail –f:to read mails send to secondary mailbox

79) emacs    :full screen editor

80) echo       : echo the text string to on monitor

81) file         : classify the file type

82) expr       : evaluates the arguments, used to do arithmetic,etc in the shell

83) find         : find files, matching a type or pattern

84) Hostname         : display or set the name of the current machine

85)ln                           : link the source to target

86)lpq ,lpstat          :show the status of the print jobs

87)lpr,lp                 :print to defind printer

88) lprm, cancel      : remove a print job from the print quee

89) man                 :display manual of given cmd

90)od                    :octal dump a binary file,in octal,ASCII,hex,decimal or char

91)passwd             :to set or change password

92) pr                    : filter the file and print it on the terminal

93) rcp hostname   : remotely copy files from this machine to another machine

94) rlogine hostname: login remotely to another machine

95) rsh hostname   : remote shell to run on another machine

96) script file                   : saves everything that appears on the screen to file until exit is executed

97) source file                  : read cmds from the file and execute them in the current shell

98) string file                               : used to search binary files for ASCII strings

99) Sty                                         : set or display terminal control options

100) uudecode file                      : decode a uuencoded file, recreating the original file

101) uuencode new name              : encode the binary file to 7-bit ASCII,usefull when sending via email, to be Decode as new name at destination

102) vi                    : visual ,full screen editor

103) jobs                : display background and suspended processes

104) kill %1            : remove suspended process #1

105) top                 : display the current, most computer-intensive commands

106) osview            : display the operating system statistics

107) setenv            : list environmental variables






What is meant by passwd file?

This file maintains each and every user information with 7 fields. The 7 fields are Username: passwd: uid: gid: fullname: home: shell.

What is Shell?

Shell is a command line interpreter. Shell acts as an interface between user and the kernel.

What is Kernel?

Kernel is core part of  UNIX o/s. It is a group of hundreds of system calls.

What are different flavors of Unix o/s?

Any operating system designed based on unix kernel called as flavour of unix. The following are some flavours of unix

Linux —- Red Hat

Sun solaris — Sun Microsystem


Hp-ux —– HP

Sco-unix —– santa crus operations

IRIX—— Silicon Graphics.


What are the different security features in Unix?


  1. Password protection.
  2. File permissions.
  3. Encryption.


What’s the command to find out today’s date?

What’s the command to find out users on the system?

How do you find out the current directory you’re in?

What is the command to see the location of command?

Where is  <command name>

How do you find out your own username? 

Whoami    (or) log name
How to close the current user account?


How to create empty file?

Touch <filename>

How do you remove a file?

Rm <filename>

How to join multifile files vertically?

Cat   file1 file2 file3 ……

The file for which we do not have write permission can be deleted using the command?

rm -f  <filename>

How do you remove a directory and its subdirectories?

rm –rf <directoryname>

How to rename a file?

Mv <filename>

How to copy multiple files and directories into some other directory?
cp -r source_directory destination_directory

How to see hodden files?

Ls –a

How to see files and subdirectories files recursively?

Ls –R

How to see files in long list format page wise?

Ls –l | more

How to identify whether a file is normal file or directory?
$ls -l filename/directoryname

if the first digit is – then it is file,

if it is d then it is directory file


What is the difference between “ls -r” and “ls -R”?

ls -r lists the files in reverse alphabetical order… whereas ls -R lists the files and directories recursively

The difference between a soft link and a hard link?
A symbolic (soft) linked file and the targeted file can be located on the same or different file system while for a hard link they must be located on the same file system.
what are the different commands used to create files?

1.touch – to create empty files (e.g) – touch <filename>

2.vi <filename>

  1. cat>filename

List some wild card characters?

? -à Iit matches any single character

* -à It matches zero or more characters

[] -à It matches any single character in given list

. –à It matches any single character except enter key character

what is the output of the follwing command : ls [a-mno-r]*

list all the files in the current directory starting alphabet

is between a to m  or n or between o to r

How do you count words, lines and characters in a file?

Wc <filename>

which command is used to identify the type of the file?

“grep” means

Globally search a regular expression and print it


How do you search for a string inside a given file?

grep string filename

How do you search for a string inside a  current directory?

grep string *
How do you search for a string in a directory with the subdirectories recursed?

grep -r string *

Difference between grep, egrep and fgrep

grep : does not accept more then one expression

egrep : accepts more than one pattern for search. Also accepts patterns from a file.

fgrep : accepts multiple patterns both from command line and file but does not accept regular expressions only strings. It is faster than the other two and should be used when using fixed strings.

What are line patterns?

^ -à start of the line

$ -à End of the line

How to search empty lines in a given file?

Grep “^$” <filename>

How to count no of blank lines in a file?

Grep –c “^$” <filename>

How to remove Empty lines form a given file?

Grep –v “^$”  filename > temfilename

Mv  tempfilename  filename

What is pattern to search 4 digit word in a file?

Grep “\<[0-9] [0-9] [0-9] [0-9]\>” filename

What is pattern to search the line having only three characters?

Grep “^…$” filename

What is pattern to display lines ending with “$” character in a given file?

Grep “\$$” filename


How to display 2 and 4 th fileds from a given file if the delimetr is “:”?

Cut –d”:” –f  2,4 filename

How to display unique lines from a given file?

Sort –u filename

How to eliminate completely duplicate lines from a given file?

Uniq –u filename

How to remove all duplicate lines from a file?

Uniq –u filename > tempfilename

Mv  tempfilename  filename

How to delete “hello” word from a given file?

Sed “s/hello//” filename

awk Command

awk is a powful Unix command. It allows the user to manipulate files that are structured as columns of data and

Once you understand the basics of awk you will find that it is surprisingly useful. You can use it to automate things in ways you have never thought about. It can be used for data processing and for automating the application of Unix commands. It also has many spreadsheet-type functionalities.

There are two ways to run awk. A simple awk command can be run from the command line. More complex tasks should be written as awk programs (“scripts”) to a file. Examples of each are provided below.

Example: % awk ‘pattern {action}’ input-file > output-file

meaning: take each line of the input file; if the line contains the pattern apply the action to the line and write the resulting line to the output-file.

If the pattern is omitted, the action is applied to all lines:

How to compare two files are same or not?


How to display the first 10 lines from a file?

Head  -10  filename

Write a one line command to convert all the capital letters of a file “test” into lower case?

cat filename | tr “[A-Z]”  “[a-z]”

The pipeline to list the five largest files in the current directory is

ls -l | tr -s ‘ ‘ | sort -t ‘ ‘ -fnr +4 -5 | head –5

The pipeline to find out the number of times the character ? occurs in the file is

tr -dc ‘?’ < file | wc -c   ( Delete all the characters except ? and then make a word count.)

How to count total no. of users working in the system?

Who | wc –l

How to display the lines from 5 to 10 from a given file?

Head -10 filename | tail +5

what will be output of following command?

echo “Tecnosoft” | wc –c


What is the default umask?


What is the default permission for File & Directory ?

The Default privileges for file : 644

The default privileges for directory :  755

What UNIX command will control the default file permissions when files are created?

Explain the read, write, and execute permissions on a UNIX directory.

Read allows you to see and list the directory contents.

Write allows you to create, edit and delete files and subdirectories in the directory.

Execute gives you the previous read/write permissions plus allows you to change into the directory and execute programs or shells from the directory.
What is chmod, chown and chgrp?

Chmod : It is used for to change permissions on files

Chown : It is used for to change ownership of a file

Chgrp : It is used for to change group of the file

If the owner doesn’t have write permission on a file, but his/her group has, can he/she edit it?

No. He/she can’t,because the owner’s permission overrides the group’s.

To see list of files and directories ,what permission required?

Read permission
What are PIDs?

They are process IDs given to processes. A PID can vary from 0 to 65535.
How do you list currently running process?

How do you stop a background process?

kill pid
How do you find out about all running processes?

ps -ag
How do you stop all the processes, except the shell window?

kill 0
How do you fire a process in the background?

./process-name &

What does the command “kill -9 $! ” do?

kills the last background process

if there is a process u want to run even after exiting the shell what is the

command used?



 which command will get executed even after you log out?



which signal cannot be trapped?

kill –9

How to redirect standard error to a file? Answer
2> filename

What does the top command display?

top command displays the current ammount of memory occupied by the currently executing processes and the details. In addition to memory usage top command displays cpu usage and process details


What is the command to send message to all users who are logged in?


What is the command to send mail to other user?

Mail username

How to open secondary mail box?

Mail -f

What do you do if you don’t want to be interrupted by other users’ messages?

Ans. mesg n

Shell Scripting Interview questions

Difference between the output of echo ** and echo * *

echo ** lists all the filenames in the current directory..

echo * * lists all the filenames in the current directory twice.

The other way of running shell script apart from using sh command and chmod?


ans:- using ! we can run a shell script


  1. How do you refer to the arguments passed to a shell script? – $1, $2 and so on. $0 is your script name.
    20. What’s the conditional statement in shell scripting? – if {condition} then … fi
    21. How do you do number comparison in shell scripts? – –eq, -ne, -lt, -le, -gt, -ge
    22. How do you test for file properties in shell scripts? – –s filename tells you if the file is not empty, -f filename tells you whether the argument is a file, and not a directory, -d filename tests if the argument is a directory, and not a file, -w filename tests for writeability, -r filename tests for readability, -x filename tests for executability
    23. How do you do Boolean logic operators in shell scripting? – ! tests for logical not, -a tests for logical and, and -o tests for logical or.
    24. How do you find out the number of arguments passed to the shell script? – $#
    25. What’s a way to do multilevel if-else’s in shell scripting? – if {condition} then {statement} elif {condition} {statement} fi
    26. How do you write a for loop in shell? – for {variable name} in {list} do {statement} done
    27. How do you write a while loop in shell? – while {condition} do {statement} done
    28. How does a case statement look in shell scripts? – case {variable} in {possible-value-1}) {statement};; {possible-value-2}) {statement};; esac
    29. How do you read keyboard input in shell scripts? – read {variable-name}
    30. How do you define a function in a shell script? – function-name() { #some code here return }
    31. How does getopts command work? – The parameters to your script can be passed as -n 15 -x 20. Inside the script, you can iterate through the getopts array as while getopts n:x option, and the variable $option contains the value of the entered option.

Batch file:

Batch files allow MS-DOS and Microsoft Windows users to create a lists of commands to run in sequence once the batch file has been executed. For example, a batch file could be used to run frequently run commands, deleting a series of files, moving files, etc. A simple batch file does not require any special programming skills and can be done by users who have a basic understanding of MS-DOS commands.

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