What does wait system call do?

Question

BlackTom AI · Accepted Answer

Clarifying the question: What does the wait system call do? This prompt asks us to evaluate each proposed description of a system call’s behavior and identify which one matches wait.
Option 1: 'Send a specified signal (such as SIGTERM) to a process identified by its PID, allowing the process to be terminated or otherwise controlled.' This describes a signal-delivery mechanism (often via kill or tgkill), not the wait call. It does not involve suspending the caller until a child finishes, so it’s inaccurate for wait.
Option 2: 'Suspend the execution of the calling (parent) process until one of its child processes terminates, then return the child’s PID and exit status.' This matches the classic wait behavior: the parent is blocked, it waits for a child to change state (usually termination), and on return provides the child PID and its exit status. The description lines up with the intended effect of wait.
Option 3: 'Replace the current process image with a new program. The PID stays the same, but the code, data, and stack are completely overwritten.' This describes exec (such as execve), not wait. It specifically mentions replacing the image without changing the PID, which is characteristic of exec, not wait.
Option 4: 'Create a new process by duplicating the calling process. The child has a new PID but initially shares the same memory image and open files as the parent.' This is a description of fork, or perhaps vfork with differences, but not wait. It emphasizes process creation and shared resources, not waiting on a child’s termination.
Putting together these assessments, only Option 2 accurately describes the wait system call’s role of blocking the parent until a child terminates and then returning information about that child. Each other option points to a different system call with distinct semantics (signal sending, exec, and fork respectively).

What does wait system call do?单项选择题

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