Tutorials

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Thursday, November 29, 2007

Unix Shell Scripting Interview Questions - 1
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• How do you find out what’s your shell? - echo $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@mindgrillq.com -s ‘Your
subject’ -c ‘cc@mindgrillq.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.