Shell Scripting Interview Questions and Answers : Shell scripting is a powerful tool that can help automate tasks and increase productivity. A shell script is a program that is written in a shell programming language, such as Bash, that is interpreted by a shell. The shell is a command-line interface that provides a way to interact with your computer’s operating system. With shell scripting, you can write scripts to automate tasks, such as installing software, backing up files, or running a series of commands. In this article, having a clear understanding of the latest Shell Scripting Interview Questions can be the key to landing your good job. That’s why we have compiled a list of the top 63 Shell Scripting Interview Questions and Answers for beginners, which cover a wide range of topics and scenarios.
Shell Scripting Interview Questions for Freshers
Q1. What is a shell script ?
A shell script is a program written in a scripting language that runs in a Unix/Linux shell. It is a sequence of commands that are executed in a particular order to automate a specific task or set of tasks.
Q2. What are the advantages of using shell scripts ?
Some advantages of using shell scripts are:
- Automation of repetitive tasks: Shell scripts can automate a set of commands that need to be executed repeatedly, saving time and reducing the risk of errors.
- Easy to learn: Shell scripting is easy to learn and understand, even for beginners with little programming experience.
- Flexibility: Shell scripts can be used to automate a wide variety of tasks, from simple file management to complex system administration tasks.
- Portability: Shell scripts can be run on different Unix/Linux platforms, making them highly portable.
Q3. What are the different types of shells in Linux ?
The different types of shells in Linux are:
- Bash (Bourne-Again SHell): The most widely used shell in Linux.
- sh (Bourne Shell): The original Unix shell.
- csh (C Shell): A shell with a C-like syntax.
- ksh (Korn Shell): An improved version of sh with additional features.
Q4. How do you write a simple shell script ?
Here is an example of a simple shell script that prints “Hello, World!” to the terminal:
#!/bin/bash echo "Hello, World!"
Q5. What is the syntax for writing comments in a shell script ?
To write comments in a shell script, use the hash symbol (#) at the beginning of the line:
# This is a comment
Q6. What is the difference between $ and # in a shell script ?
In a shell script, the $ symbol is used to reference a variable, while the # symbol is used to reference the number of command-line arguments passed to the script.
Q7. What is the difference between a shell script and a shell program ?
A shell script is a program written in a scripting language that runs in a Unix/Linux shell, while a shell program is a program that interacts with the Unix/Linux shell.
Q8. What is the difference between shell and kernel in Linux ?
The shell is the interface between the user and the kernel, while the kernel is the core of the operating system that manages the system’s resources and provides low-level services to other parts of the system.
Q9. What are the various ways to execute a shell script ?
There are several ways to execute a shell script:
- Run the script as an executable file: Make the script executable using the chmod command and then run it directly from the command line.
- Run the script using the shell interpreter: Run the script using the shell interpreter by typing “bash script.sh” or “sh script.sh”.
- Run the script using the source command: Run the script using the source command by typing “. script.sh”.
Q10. How do you debug a shell script ?
To debug a shell script, you can use the set -x command to turn on debugging mode, which will display each command as it is executed.
Q11. What are control instructions ?
Control instructions are commands in a shell script that control the flow of execution, such as if/then statements and loops. They allow the script to make decisions and repeat tasks based on specific conditions.
Q12. What is a shebang line in a shell script ?
The shebang line in a shell script is the first line of the script that begins with #! (hash bang or shebang). It specifies the path to the interpreter that should be used to execute the script.
Top 50 Shell Scripting Interview Questions And Answers
Q13. What is the use of the chmod command in shell scripting ?
The chmod command is used to change the permissions of a file or directory in shell scripting. It allows the user to add or remove read, write, or execute permissions for the owner, group, and others.
Q14. What is a symbolic link in Linux ?
A symbolic link, also known as a symlink, is a type of file that points to another file or directory in Linux. It acts as a shortcut to the original file or directory and allows the user to access it from a different location.
Q15. What is the difference between hard link and soft link in Linux ?
The main difference between a hard link and a soft link (symbolic link) in Linux is that a hard link points directly to the inode of a file, whereas a soft link points to the file name. This means that if the original file is deleted, a hard link will still be able to access the file contents, while a soft link will become invalid.
Q16. How do you declare a variable in a shell script ?
To declare a variable in a shell script, use the syntax variable_name=value. For example, to declare a variable named “name” with the value “John”, use the command “name=John”.
Q17. What are the different types of variables in shell scripting ?
There are three types of variables in shell scripting:
Local variables are defined and used within a single shell script.
Environment variables are available to any process started by the shell.
Shell variables are predefined variables that are set by the shell or the user.
Q18. How do you pass arguments to a shell script ?
To pass arguments to a shell script, include them after the script name when calling it. For example, to pass two arguments to a script named “myscript.sh”, use the command “myscript.sh arg1 arg2”.
Q19. How will you debug a shell script ?
To debug a shell script, use the “set -x” command to enable debugging mode, which will print each command as it is executed. You can also use the “echo” command to print variable values and check for syntax errors.
Q20. How do you use if-else statements in a shell script ?
To use if-else statements in a shell script, use the syntax “if condition; then command1; else command2; fi”. For example, to check if a variable named “age” is greater than 18, use the command “if [ $age -gt 18 ]; then echo “Adult”; else echo “Minor”; fi”.
Q21. How can we create a function in shell script ?
To create a function in a shell script, use the syntax “function_name() { commands }”. For example, to create a function named “greet” that prints a greeting message, use the command “greet() { echo “Hello, World!”; }”.
Q22. Write the difference between $$ and $! ?
$$ is a special shell variable that stores the process ID of the current shell, while $! stores the process ID of the last background command executed.
Q23. How do you use the case statement in a shell script ?
The case statement in a shell script is used to test a variable against multiple patterns and execute different commands depending on the match. Use the syntax “case variable in pattern1) command1;; pattern2) command2;; esac”.
Top 40 Shell Scripting Interview Questions And Answers
Q24. How do you use loops in a shell script ?
To use loops in a shell script, use the “for” and “while” loops. The “for” loop is used to iterate over a list of items, while the “while” loop is used to execute commands as long as a condition is true. Use the syntax “for item in list; do commands; done” for a for loop, and “while condition; do commands; done” for a while loop.
Q25. What is the difference between while and until loops in a shell script ?
The difference between while and until loops in a shell script:
While loops execute the code inside the loop as long as the specified condition is true. Until loops, on the other hand, execute the code inside the loop until the specified condition becomes true.
Q26. What is the use of the break statement in a shell script ?
The use of the break statement in a shell script:
The break statement is used to exit a loop prematurely. When a break statement is encountered inside a loop, the loop is terminated immediately, and the program control moves to the next statement after the loop.
Q27. What is the use of the continue statement in a shell script ?
The use of the continue statement in a shell script:
The continue statement is used to skip the remaining code inside the loop for the current iteration and move on to the next iteration.
Q28. What is the use of the exit command in a shell script ?
The use of the exit command in a shell script:
The exit command is used to terminate a shell script immediately. It is typically used to exit the script with an exit status that indicates whether the script executed successfully or encountered an error.
Q29. What is the difference between echo and printf commands in shell scripting ?
The difference between echo and printf commands in shell scripting:
The echo command is used to display a message on the terminal. The printf command is used to format and print a message to the terminal.
Shell Scripting Interview Questions for Experienced
Q30. What is the use of the cut command in shell scripting ?
The use of the cut command in shell scripting:
The cut command is used to extract specific sections of text from a file or input stream based on a delimiter or a fixed position.
Q31. What is the use of the grep command in shell scripting ?
The use of the grep command in shell scripting:
The grep command is used to search for a specific pattern in a file or input stream and display the lines that match the pattern.
Q32. What is the use of the sed command in shell scripting ?
The use of the sed command in shell scripting:
The sed command is used to perform text transformations on a file or input stream. It can be used to replace text, delete lines, or insert text into a file.
Q33. What is the use of the awk command in shell scripting ?
The use of the awk command in shell scripting:
The awk command is used to perform text processing and data manipulation on a file or input stream. It can be used to extract specific fields from a file, perform arithmetic operations, and print formatted output.
Q34. Write the difference between $* and $@ ?
The difference between $* and $@:
$* and $@ both represent all the positional parameters passed to a shell script, but they have different behaviors when they are enclosed in double quotes. $* expands to a single string containing all the positional parameters separated by the first character in the IFS (Internal Field Separator) variable, while $@ expands to separate strings, each containing one positional parameter.
Q35. What is the use of the sort command in shell scripting ?
The use of the sort command in shell scripting:
The sort command is used to sort the lines of a file or input stream based on a specific criterion, such as alphabetical order, numerical order, or the order of specific fields.
Q36. What is the use of the uniq command in shell scripting ?
The use of the uniq command in shell scripting:
The uniq command is used to remove duplicate lines from a file or input stream.
Q37. What is the use of the “$?” command ?
The use of the “$?” command:
The “$?” command is a special shell variable that contains the exit status of the last executed command. The exit status is an integer value that indicates whether the command executed successfully or encountered an error. A value of 0 indicates success, while non-zero values indicate errors.
Q38. What is the use of the wc command in shell scripting ?
The wc command in shell scripting is used to count the number of lines, words, and characters in a file.
Q39. What is the use of the diff command in shell scripting ?
The diff command in shell scripting is used to compare two files and show the differences between them.
Q40. What is the use of the tar command in shell scripting ?
The tar command in shell scripting is used to create and manipulate archives. It can be used to combine multiple files into a single archive, compress files, and extract files from an archive.
Q41. What is the use of the zip command in shell scripting ?
The zip command in shell scripting is used to compress and archive files in a ZIP format. It can also be used to extract files from a ZIP archive.
Q42. What is the importance of $# ?
The $# is a special variable in shell scripting that represents the number of arguments passed to a script or function.
Top 20 Shell Scripting Interview Questions And Answers
Q43. How do you create a function in a shell script ?
To create a function in a shell script, you need to use the function keyword followed by the function name and the function body enclosed in curly braces. For example:
function my_function() {
# function body
}
Q44. What is the use of the return statement in a shell script function ?
The return statement in a shell script function is used to return a value to the calling program. It is similar to the return statement in other programming languages.
Q45. What is the use of the local command in a shell script function ?
The local command in a shell script function is used to declare a variable that is only accessible within the function. It allows you to create local variables that do not interfere with global variables of the same name.
Q46. How do you pass arguments to a shell script function ?
Arguments can be passed to a shell script function by including them as parameters when calling the function. For example:
my_function arg1 arg2 arg3
Q47. How do you call a shell script function ?
To call a shell script function, you simply need to type the function name followed by any required parameters. For example:
my_function arg1 arg2 arg3
Q48. What is the use of the export command in shell scripting ?
The export command in shell scripting is used to make a variable available to other scripts and programs that are called from the current script.
Q49. What is the use of the source command in shell scripting ?
The source command in shell scripting is used to execute the contents of a script file within the current shell. It is commonly used to set environment variables and configure the shell.
Q50. How do you use pipes in shell scripting ?
Pipes are used in shell scripting to redirect the output of one command as input to another command. The | symbol is used to create a pipe. For example:
command1 | command2
In this example, the output of command1 is used as input to command2.
Q51. What is the use of the tee command in shell scripting ?
The tee command in shell scripting is used to read the standard input and write it to both standard output and a file, simultaneously. It is often used in combination with other commands to save output to a file while also displaying it on the screen.
Q52. What is the use of the xargs command in shell scripting ?
The xargs command in shell scripting is used to read items from standard input, separated by whitespace or newlines, and pass them as arguments to a specified command. It is often used in combination with other commands to perform operations on a set of files or directories.
Top 10 Shell Scripting Interview Questions And Answers
Q53. What is the use of the find command in shell scripting ?
The find command in shell scripting is used to search for files and directories in a specified location, based on a set of criteria such as name, type, size, and modification time. It is often used to perform batch operations on files or to locate specific files in a complex directory structure.
Q54. What is the use of the locate command in shell scripting ?
The locate command in shell scripting is used to quickly search for files and directories on the system, based on a database of file names and locations. It is faster than find, but the database needs to be periodically updated to ensure accurate results.
Q55. What is the use of the which command in shell scripting ?
The which command in shell scripting is used to locate the executable file associated with a given command or program. It searches the directories listed in the PATH environment variable to find the first occurrence of the specified command.
Q56. What is the use of the type command in shell scripting ?
The type command in shell scripting is used to determine the type of a command or program. It can identify whether a command is a built-in shell command, an alias, a function, or an external program.
Q57. What is the use of the alias command in shell scripting ?
The alias command in shell scripting is used to create shortcuts for longer or more complex commands. It allows users to define their own custom commands or to modify the behavior of existing commands.
Q58. What is the use of the history command in shell scripting ?
The history command in shell scripting is used to display a list of commands that have been entered by the user during the current session or in previous sessions. It can be used to recall previous commands or to repeat a command from the history list.
Q59. What is the use of the source command in shell scripting ?
The source command in shell scripting is used to execute commands or scripts in the current shell environment, rather than in a new shell environment. It is often used to load environment variables or to execute shell scripts that define functions or aliases.
Q60. What is the use of the export command in shell scripting ?
The export command in shell scripting is used to create environment variables that can be accessed by other processes or scripts. It allows users to set variables that are visible to all child processes of the current shell.
Q61. What is the use of the set command in shell scripting ?
The set command in shell scripting is used to modify the behavior of the shell environment. It can be used to set options or variables that affect how commands are executed or how input and output are handled.
Q62. What is the use of the unset command in shell scripting ?
The unset command in shell scripting is used to remove environment variables or shell options that have been previously set. It is often used to clean up the environment before executing a command or script.
Q63. What is the use of the trap command in shell scripting ?
The trap command in shell scripting is used to set up signal handlers for the shell environment. It allows users to define how the shell should respond to signals such as SIGINT (interrupt signal) or SIGTERM (termination signal) that are sent to the shell.
The Top 63 Shell Scripting Interview Questions and Answers provide comprehensive coverage of the latest technical interview topics, ensuring aspirants are well-prepared for any automate tasks and increase productivity role. To acquire further knowledge, we encourage you to follow us at fresherstech.com.
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