Quiz for Error handling errno

Q1: What is errno in C?

A. A global variable indicating error codes B. A function to handle errors C. A macro to ignore errors D. A library for error handling

Q2: Which header file defines errno?

A. errno.h B. error.h C. stdio.h D. stdlib.h

Q3: What is the value of errno when there is no error?

A. 0 B. -1 C. NULL D. 1

Q4: Is errno reset automatically after a successful function call?

A. No B. Yes C. Depends on compiler D. Only in debug mode

Q5: Which function can be used to print human-readable error messages?

A. perror B. printf C. scanf D. fopen

Q6: How to reset errno?

A. Set errno to 0 explicitly B. Call perror C. Call clearerr D. Call exit

Q7: Which of the following is NOT a valid use of errno?

A. Checking error code after function failure B. Ignoring errors C. Debugging errors D. Providing error info to user

Q8: errno is typically defined as:

A. an integer B. a float C. a pointer D. a character

Q9: Which function sets errno on failure?

A. open B. main C. printf D. strlen

Q10: Can errno be used in multithreaded programs safely?

A. Yes, if thread-local errno is used B. No, never C. Only in main thread D. Only in Linux

Q11: What does the perror function output?

A. A descriptive error message to stderr B. A number C. A variable value D. Nothing

Q12: What is a common cause of errno being set?

A. System call failure B. Successful function execution C. Variable initialization D. Compilation errors

Q13: Which errno value represents "file not found"?

A. ENOENT B. EACCES C. EINVAL D. ENOMEM

Q14: Which function can clear the error indicator on a FILE stream?

A. clearerr B. perror C. fclose D. fopen

Q15: errno should be checked:

A. Immediately after a function that can fail B. Before any function call C. Only at program start D. Only during debugging

Q16: What happens if you use errno without including errno.h?

A. Compilation error or undefined behavior B. Works fine C. Runtime error D. Warning only

Q17: Which errno value means "Permission denied"?

A. EACCES B. ENOENT C. EINVAL D. ENOMEM

Q18: How can you handle errors portably using errno?

A. Check errno after function failure and handle accordingly B. Ignore all errors C. Set errno manually to nonzero D. Print errno only

Q19: Which function can map errno values to error strings?

A. strerror B. perror C. printf D. scanf