c - mkfifo 文件权限未正确执行

Question

我的 C 程序中的以下行应提供 All/Group/Owner 读写权限

mkfifo("/tmp/dumbPipe", 0666)

但是一旦我执行了代码并检查了未设置写入位的权限，我最终得到了

prw-r--r-- 

所有者是相同的，这是一个问题，因为我在 tmp 目录中创建管道吗？当我从 cmd 行运行 chmod 666 时，所有权限都已正确设置。

Answer 1

这是一个没有评论的帖子，只是引用手册。简洁等

引自 man 3 mkfifo:

It is modified by the process's umask in the usual way: the permissions of the created file are (mode & ~umask).

引自 man 2 umask

The typical default value for the process umask is S_IWGRP | S_IWOTH (octal 022). In the usual case where the mode argument to open(2) is specified as:

      S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH

  (octal 0666) when creating a new file, the permissions on the resulting file will be:

      S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH

  (because 0666 & ~022 = 0644; i.e., rw-r--r--).