删除文件在读取目录中READDIR（） [英] Delete files while reading directory with readdir()

问题描述

我的code是这样的：

My code is something like this:

DIR* pDir = opendir("/path/to/my/dir");
struct dirent pFile = NULL;
while ((pFile = readdir())) {
   // Check if it is a .zip file
   if (subrstr(pFile->d_name,".zip") {
      // It is a .zip file, delete it, and the matching log file
      char zipname[200];
      snprintf(zipname, sizeof(zipname), "/path/to/my/dir/%s", pFile->d_name);
      unlink(zipname);
      char* logname = subsstr(zipname, 0, strlen(pFile->d_name)-4); // Strip of .zip
      logname = appendstring(&logname, ".log"); // Append .log
      unlink(logname);
}
closedir(pDir);

（此code是未经考验的，纯粹的例子）

(this code is untested and purely an example)

问题的关键是：是否允许删除一个文件目录中，同时通过与目录循环readdir的（）？
或将READDIR（）仍然发现删除.log文件？

The point is: Is it allowed to delete a file in a directory while looping through the directory with readdir()? Or will readdir() still find the deleted .log file?

推荐答案

引用自 POSIX readdir的：

如果一个文件被去除或添加到
  后的最新的目录
  调用执行opendir（）或rewinddir（）
  无论后续调用READDIR（）
  返回该文件的条目
  不确定的。

If a file is removed from or added to the directory after the most recent call to opendir() or rewinddir(), whether a subsequent call to readdir() returns an entry for that file is unspecified.

所以，我的猜测是...这要看情况。

So, my guess is ... it depends.

这取决于OS的不同，一天中的时间，对添加的文件的相对顺序/删除，...

It depends on the OS, on the time of day, on the relative order of the files added/deleted, ...

和，作为进一步的点，时间之间的 READDIR（）函数返回，并尝试取消链接（）该文件，其他进程可能已经删除该文件，你的取消链接（）失败。

And, as a further point, between the time the readdir() function returns and you try to unlink() the file, some other process could have deleted that file and your unlink() fails.

---

的修改的

我用此程序进行测试：

#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>

int main(void) {
  struct dirent *de;
  DIR *dd;

  /* create files `one.zip` and `one.log` before entering the readdir() loop */
  printf("creating `one.log` and `one.zip`\n");
  system("touch one.log"); /* assume it worked */
  system("touch one.zip"); /* assume it worked */

  dd = opendir("."); /* assume it worked */
  while ((de = readdir(dd)) != NULL) {
    printf("found %s\n", de->d_name);
    if (strstr(de->d_name, ".zip")) {
      char logname[1200];
      size_t i;
      if (*de->d_name == 'o') {
        /* create `two.zip` and `two.log` when the program finds `one.zip` */
        printf("creating `two.zip` and `two.log`\n");
        system("touch two.zip"); /* assume it worked */
        system("touch two.log"); /* assume it worked */
      }
      printf("unlinking %s\n", de->d_name);
      if (unlink(de->d_name)) perror("unlink");
      strcpy(logname, de->d_name);
      i = strlen(logname);
      logname[i-3] = 'l';
      logname[i-2] = 'o';
      logname[i-1] = 'g';
      printf("unlinking %s\n", logname);
      if (unlink(logname)) perror("unlink");
    }
  }
  closedir(dd); /* assume it worked */
  return 0;
}

在我的电脑上， READDIR（）查找删除的文件并没有找到之间建立执行opendir文件（）和 READDIR（）。但也可以是另一台计算机上的不同;它可能是，如果我编译使用不同的选项在我的电脑上的不同;它可能是不同的，如果我升级内核; ...

On my computer, readdir() finds deleted files and does not find files created between opendir() and readdir(). But it may be different on another computer; it may be different on my computer if I compile with different options; it may be different if I upgrade the kernel; ...

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