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ES (extensible shell) is a lightweight, advanced, extensible command language interpreter or shell. It was developed as a direct descendant of the UNIX Thompson Shell and is based on the RC shell. ES offers several sophisticated programming features aimed at improving productivity and enhancing user control including higher-order functions and exception handling. It incorporates an improved syntax that supports floating-point arithmetic operations, string manipulation, process control among other features. This makes it suitable for both interactive use and scripting tasks. The 'extensibility' in its name refers to its design philosophy that allows users to tailor their environment according to their specific needs by extending or modifying the shell's capabilities using scripts written in its own language. Despite being powerful, ES maintains a small memory footprint which makes it faster than many other shells while offering similar functionalities. It can run on most Unix-like operating systems including Linux distributions.

Ask the right questions secure the right ES (extensible shell) talent among an increasingly shrinking pool of talent.

First 20 minutes

General ES (extensible shell) app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in ES (extensible shell) application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What is your experience with ES (extensible shell)?

I have been working with ES for over 5 years, developing complex shell scripts for various applications.

How would you debug a script in ES?

I would use the 'trace' command to track the execution of the script. I would also use 'echo' statements to print out variable values at different stages of the script.

What are some advantages of using ES over other shells?

ES is highly extensible and customizable. It supports higher-level programming constructs, making it easier to write complex scripts. It also has better string handling capabilities compared to other shells.

Describe the difference between a shell and a terminal.

A shell is a command line interpreter that provides a user interface for access to an operating system's services. A terminal, on the other hand, is a physical device or software application that is used to access the shell.

How would you handle errors in an ES script?

I would use 'try' and 'catch' blocks to handle errors. I would also make use of the 'errno' variable to get more information about the error.

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What you’re looking for early on

Does the candidate have a strong understanding of ES (extensible shell)?

Has the candidate demonstrated problem-solving skills?

Can the candidate communicate effectively?

Does the candidate have experience with other shell scripting languages?

Next 20 minutes

Specific ES (extensible shell) development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

What are some common uses of shell scripting?

Shell scripting is commonly used for automating repetitive tasks, managing system resources, and for developing software and tools.

Describe the difference between a function and a procedure in ES.

In ES, a function is a named sequence of commands that returns a value, while a procedure is a named sequence of commands that performs an action but does not return a value.

How would you optimize a slow-running ES script?

I would first use profiling tools to identify the bottlenecks in the script. Then, I would look for ways to optimize these parts of the script, such as by reducing unnecessary computation or by using more efficient data structures.

What are some security best practices when writing ES scripts?

Some best practices include avoiding the use of eval, checking all input for injection attacks, and using secure temporary files.

Describe the difference between a local and a global variable in ES.

A local variable is only accessible within the block of code where it is defined, while a global variable is accessible throughout the entire script.

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At this point, a skilled ES (extensible shell) engineer should demonstrate strong problem-solving abilities, proficiency in ES (extensible shell) programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with ES (extensible shell).

What does the following simple ES code do?
fn greet { echo 'Hello, World!' }
This code defines a function named 'greet'. When this function is called, it outputs the string 'Hello, World!' to the console.
What will be the output of the following ES code?
let x = 10
let y = 20
if {~ $x $y} { echo 'Equal' } else { echo 'Not Equal' }
This code will output 'Not Equal'. It first assigns the values 10 and 20 to the variables x and y respectively. It then checks if x and y are equal using the '~' operator. If they are equal, it outputs 'Equal'. If not, it outputs 'Not Equal'.
What does this ES code do?
let numbers = [1 2 3 4 5]
for i in $numbers { echo $i }
This code declares an array 'numbers' with elements 1 to 5. It then iterates over each element in the array with a for loop, and outputs each element to the console.
What will be the output of the following ES code?
@ { echo 'Start'
sleep 2
echo 'End' } &
 echo 'Running in background'
This code will output 'Start', then 'Running in background', and after a delay of 2 seconds, it will output 'End'. The '@' operator is used to run the block of code in the background, hence 'Running in background' is printed before 'End'.

Wrap-up questions

Final candidate for ES (extensible shell) Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle ES (extensible shell) application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you test an ES script?

I would write unit tests for individual functions and integration tests for the entire script. I would also use tools like shellcheck to check for common errors and best practices.

What are some ways to improve the readability of an ES script?

Some ways to improve readability include using meaningful variable and function names, adding comments to explain complex parts of the script, and following a consistent coding style.

Describe the difference between synchronous and asynchronous commands in ES.

Synchronous commands are executed one after the other, with each command waiting for the previous one to finish before starting. Asynchronous commands, on the other hand, are started in the background and do not wait for other commands to finish.

ES (extensible shell) application related

Product Perfect's ES (extensible shell) development capabilities

Beyond hiring for your ES (extensible shell) engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in ES (extensible shell) projects, and can engage in multiple capacities.

ES (extensible shell) Consultive assessments

ES (extensible shell) Application Conversion Assessment ES (extensible shell) Application Integration Assessment ES (extensible shell) Data & Database Integration Assessment

Custom ES (extensible shell) development projects

Custom ES (extensible shell) App Conversion ES (extensible shell) Custom App Development Process App UI Design for ES (extensible shell) Facelifts

Hiring guide for ES (extensible shell) Engineers

ES (extensible shell) Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the ES (extensible shell) engineer at this point.

ES (extensible shell) Consultive assessments

Custom ES (extensible shell) development projects