Basic shell scripting questions

  1. How do you find out what’s your shell? - echo $SHELL
  2. What’s the command to find out today’s date? - date
  3. What’s the command to find out users on the system? - who
  4. How do you find out the current directory you’re in? - pwd
  5. How do you remove a file? - rm
  6. How do you remove a - rm -rf
  7. How do you find out your own username? - whoami
  8. How do you send a mail message to somebody? - mail somebody@techinterviews.com -s ‘Your subject’ -c ‘cc@techinterviews.com
  9. How do you count words, lines and characters in a file? - wc
  10. How do you search for a string inside a given file? - grep string filename
  11. How do you search for a string inside a directory? - grep string *
  12. How do you search for a string in a directory with the subdirectories recursed? - grep -r string *
  13. What are PIDs? - They are process IDs given to processes. A PID can vary from 0 to 65535.
  14. How do you list currently running process? - ps
  15. How do you stop a process? - kill pid
  16. How do you find out about all running processes? - ps -ag
  17. How do you stop all the processes, except the shell window? - kill 0
  18. How do you fire a process in the background? - ./process-name &
  19. 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.
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9 Comments on Basic shell scripting questions

  1. Rajkumar
    Posted 7/31/2007 at 11:22 pm | Permalink

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

    if not linux use the below command

    find / |xargs grep “string”

  2. Eswara moorthy
    Posted 8/10/2007 at 5:37 pm | Permalink

    How do u find the process ID for all services??

    pgrep

    eg:pgrep mysql

  3. teacher
    Posted 8/17/2007 at 1:18 pm | Permalink

    1) There are many shell scripting languages based on the shell being used.
    2) Syntax for the scripting is based on the shell.
    3) The syntax above would work for Bourne shell but many would not work for the “C” shell “csh”.

  4. Shiv
    Posted 10/26/2007 at 12:41 pm | Permalink

    find ./ -exec grep “string” {} \;

  5. Adam
    Posted 3/5/2008 at 4:42 pm | Permalink

    Hey guys i’m just wondering. i’m thinking about getting into game scripting and basic C++ does anyone have any tips for how to get started in something like this or computer science?

  6. Posted 6/25/2008 at 11:11 am | Permalink

    What happens to a child process that dies and has no parent process to wait for it and what’s bad about this?

  7. Posted 9/6/2008 at 7:54 am | Permalink

    What is difference betwen shell scripting language and programing language ?

  8. Posted 11/1/2008 at 6:43 am | Permalink

    We can take an example in solaris.

    If parent process dies while running child process below said things may happen:-

    After complition of child’s process task it will search the parent process if there is no parent process it may go defunct status and it’s status will be zombie mode.

    It will take swap space & memory space and also take load average. Rspective parent process can’t not execute the particular child process in next instance. In this situation we have to kill that respective child process by manually.

  9. Posted 11/1/2008 at 6:45 am | Permalink

    If parent process dies while running child process below said things may happen:-

    After complition of child’s process task it will search the parent process if there is no parent process it may go defunct status and it’s status will be zombie mode.

    It will take swap space & memory space and also take load average. Rspective parent process can’t not execute the particular child process in next instance. In this situation we have to kill that respective child process by manually.

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