How do you find out what’s your shell? -

 ANS: Secho $SHELL

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

 - date

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

 - who

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

 - pwd

 How do you remove a file?

 - rm

 How do you remove a - rm -rf

 How do you find out your own username?

 - whoami

 How do you send a mail message to somebody?

- mail somebody@cinterviews.com -s ‘Your subject’ -c ‘cc@cinterviews.com‘

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

 - wc

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

- grep string filename

 How do you search for a string inside a directory?

 - grep string *

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

- grep -r string *

 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?

 - ps

 How do you stop a 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 &

 How do you refer to the arguments passed to a shell script?

- $1, $2 and so on. $0 is your script name.

 What’s the conditional statement in shell scripting?

 - if {condition} then … fi

 How do you do number comparison in shell scripts?

- -eq, -ne, -lt, -le, -gt, -ge

 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

 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.

 How do you find out the number of arguments passed to the shell script?

- $#

 What’s a way to do multilevel if-else’s in shell scripting?

- if {condition} then {statement} elif {condition} {statement} fi

 How do you write a for loop in shell?

 - for {variable name} in {list} do {statement} done

 How do you write a while loop in shell?

 - while {condition} do {statement} done

 How does a case statement look in shell scripts?

 - case {variable} in {possible-value-1}) {statement};; {possible-value-2}) {statement};; esac

 How do you read keyboard input in shell scripts?

 - read {variable-name}

 How do you define a function in a shell script?

 - function-name() { #some code here return }

 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.