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The GNU C Library, commonly known as glibc, is a critical component of the GNU Project first released in 1987. It serves as the core interface between an operating system and its applications in Unix-like systems including Linux. As an open-source software, it implements the standard library defined by the ISO C standard, providing developers with system call interfaces and basic functions such as string handling or mathematical operations. The project is currently maintained by a community of developers under the stewardship of the Free Software Foundation. Its historical significance and continued relevance make it a fundamental tool for modern software development.

Ask the right questions secure the right GNU C Library(glibc) talent among an increasingly shrinking pool of talent.

First 20 minutes

General GNU C Library(glibc) app knowledge and experience

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

How would you explain the role of glibc in a Linux system?

glibc is the C library which defines the system calls and other basic facilities such as open, malloc, printf, exit, etc. It is used to provide system call interface and basic functions for the operation of the Linux system.

What are the main components of glibc?

The main components of glibc are the C library, math library, POSIX thread library, GNU libio, internationalization library, and the name service switch.

Describe the difference between static and dynamic linking in glibc.

Static linking involves including all necessary library routines in the executable file while dynamic linking involves linking the routines from the library at runtime. Static linking results in larger executables that are self-contained, while dynamic linking results in smaller executables that require the library to be present on the system at runtime.

How would you use glibc to perform file I/O operations?

You can use the fopen, fread, fwrite, and fclose functions provided by glibc to perform file I/O operations. These functions allow you to open a file, read from a file, write to a file, and close a file respectively.

What are the key differences between malloc and calloc in glibc?

malloc and calloc are both used to dynamically allocate memory in glibc. The key difference is that malloc does not initialize the memory it allocates, while calloc initializes the allocated memory to zero.

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What you’re looking for early on

Does the candidate have a deep understanding of the GNU C Library?

Has the candidate demonstrated the ability to write clean, efficient, and maintainable C code?

Does the candidate have experience with debugging and performance tuning in C?

Has the candidate shown an understanding of the Linux operating system and its internals?

Next 20 minutes

Specific GNU C Library(glibc) 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.

How would you use glibc to create a new process?

You can use the fork function provided by glibc to create a new process. This function creates a new process by duplicating the existing process.

Describe the difference between pthreads and processes in glibc.

In glibc, pthreads are threads of execution within a single process, while processes are instances of a running program. Pthreads share the same memory space, while processes have their own memory space.

What are the key differences between the printf and sprintf functions in glibc?

printf and sprintf are both used to format and print data. The key difference is that printf outputs the formatted data to the standard output, while sprintf outputs the formatted data to a string.

How would you use glibc to handle signals in a program?

You can use the signal function provided by glibc to handle signals in a program. This function allows you to specify a signal handler function that will be called when the specified signal is received.

Describe the difference between the exit and _exit functions in glibc.

Both exit and _exit are used to terminate a program. The difference is that exit performs cleanup operations such as flushing buffers and calling functions registered with atexit, while _exit terminates the program immediately without performing any cleanup operations.

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At this point, a skilled GNU C Library(glibc) engineer should demonstrate strong problem-solving abilities, proficiency in GNU C Library(glibc) 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 GNU C Library(glibc).

What does the following code do?
#include 

int main() {
    printf("Hello, World!\n");
    return 0;
}
This code prints the string 'Hello, World!' to the standard output.
What will be the output of the following code?
#include 

int main() {
    int a = 10;
    int b = 20;
    printf("%d\n", a + b);
    return 0;
}
The output of the code will be '30'. The code adds the values of 'a' and 'b' and prints the result.
What does the following code do?
#include 

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    for(int i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    }
    return 0;
}
This code initializes an array of integers and then prints each element of the array to the standard output.
What does the following code do?
#include 
#include 

void *print_message(void *ptr) {
    char *message;
    message = (char *) ptr;
    printf("%s \n", message);
}

int main() {
    pthread_t thread1, thread2;
    char *message1 = "Thread 1";
    char *message2 = "Thread 2";
    pthread_create(&thread1, NULL, print_message, (void*) message1);
    pthread_create(&thread2, NULL, print_message, (void*) message2);
    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    return 0;
}
This code creates two threads, each of which prints a different message. The 'pthread_create' function starts each thread, and the 'pthread_join' function waits for each thread to finish.

Wrap-up questions

Final candidate for GNU C Library(glibc) 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 GNU C Library(glibc) application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the key differences between the qsort and bsearch functions in glibc?

qsort and bsearch are both used to manipulate arrays. qsort is used to sort an array, while bsearch is used to search for an item in a sorted array.

How would you use glibc to implement a multithreaded program?

You can use the pthread_create, pthread_join, and pthread_exit functions provided by glibc to implement a multithreaded program. These functions allow you to create a new thread, wait for a thread to terminate, and terminate a thread respectively.

Describe the difference between the setjmp and longjmp functions in glibc.

setjmp and longjmp are used to perform non-local jumps in a program. setjmp saves the current execution context into a buffer for later use by longjmp, while longjmp restores the execution context saved by setjmp and transfers control back to the point where setjmp was called.

GNU C Library(glibc) application related

Product Perfect's GNU C Library(glibc) development capabilities

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

GNU C Library(glibc) Consultive assessments

GNU C Library(glibc) Application Conversion Assessment GNU C Library(glibc) Application Integration Assessment GNU C Library(glibc) Data & Database Integration Assessment

Custom GNU C Library(glibc) development projects

Custom GNU C Library(glibc) App Conversion GNU C Library(glibc) Custom App Development Process App UI Design for GNU C Library(glibc) Facelifts

Hiring guide for GNU C Library(glibc) Engineers

GNU C Library(glibc) Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the GNU C Library(glibc) engineer at this point.

GNU C Library(glibc) Consultive assessments

Custom GNU C Library(glibc) development projects