c - 当某个进程打开文件时，unlink() 会做什么？

Question

来自 APUE

#include <unistd.h>
int unlink(const char *pathname);

Only when the link count reaches 0 can the contents of the file be deleted. One other condition prevents the contents of a file from being deleted: as long as some process has the file open, its contents will not be deleted. When a file is closed, the kernel first checks the count of the number of processes that have the file open. If this count has reached 0, the kernel then checks the link count; if it is 0, the file’s contents are deleted.

1. 如果进程中的 execve() 正在使用一个文件，它是否将其视为“进程已打开文件”？

2. 如果某个进程正在打开文件或execve()ed，unlink()会立即返回0或-1，或者等到进程关闭文件或 execve() 完成运行并执行其工作？

Answer 1

1) 进程通过 execve 继承的文件句柄将保持打开状态，直到明确关闭或进程退出。

2) unlink 不会阻塞。它将简单地删除路径并减少硬链接(hard link)文件的引用计数，此时文件系统可以删除引用的文件并在文件不再被任何进程打开后释放与其关联的空间。 unlink 将返回 0，除非出现 I/O 或权限错误等。