Process creation (fork and exec) in Operating Systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding fork() behavior

What happens immediately after a fork() system call in a Unix-like operating system?

A The child process starts executing a different program automatically.

B The parent process is replaced by a new program.

C The operating system terminates the parent process.

D A new child process is created as a copy of the parent process.

💡 Hint

Think about whether the parent process continues to run after fork().

After fork(), the operating system creates a new child process that is an exact copy of the parent process. Both processes continue running independently.

📋 Factual

intermediate

Role of exec() in process creation

What is the primary purpose of the exec() family of system calls in process creation?

A To create a new process by duplicating the current one.

B To terminate the current process and all its children.

C To replace the current process's memory space with a new program.

D To pause the current process until a child finishes execution.

💡 Hint

Consider what happens to the program code when exec() is called.

The exec() system call replaces the current process's code and data with a new program, without creating a new process.

🔍 Analysis

advanced

Output of combined fork() and exec() code

Consider the following code snippet in a Unix-like system:

pid = fork()
if pid == 0:
    exec("/bin/ls")
else:
    wait()

What is the expected behavior of this code?

A The code causes a runtime error because exec() is called incorrectly.

B The child process lists directory contents, parent waits for child to finish.

C Both parent and child list directory contents simultaneously.

D The parent process lists directory contents, child waits.

💡 Hint

Remember what fork() returns in parent and child, and what exec() does.

The child process replaces its code with /bin/ls and runs it. The parent waits for the child to finish before continuing.

❓ Comparison

advanced

Difference between fork() and exec()

Which statement best describes the difference between fork() and exec() system calls?

A <code>fork()</code> creates a new process; <code>exec()</code> replaces the current process's program.

B <code>fork()</code> replaces the current process's program; <code>exec()</code> creates a new process.

C Both <code>fork()</code> and <code>exec()</code> create new processes but in different ways.

D <code>fork()</code> terminates the current process; <code>exec()</code> pauses it.

💡 Hint

Think about whether each call creates a new process or changes the current one.

fork() duplicates the current process creating a child; exec() replaces the current process's code with a new program.

❓ Reasoning

expert

Why use fork() before exec()?

Why do most Unix-like programs use fork() followed by exec() to run a new program instead of just calling exec() directly?

A To create a new process so the original program can continue running separately.

B Because <code>fork()</code> cleans up memory before <code>exec()</code> runs.

C Because <code>exec()</code> cannot be called without <code>fork()</code> first.

D To ensure the new program runs with higher priority than the original.

💡 Hint

Consider what happens if exec() is called without fork().

Calling exec() replaces the current program, so fork() is used first to create a new process that runs the new program, allowing the original to continue.