stat(2) 和 chmod(2) 中的模式掩码名称的含义是什么？

Question

stat 调用对于模式字段中的各个位具有一系列符号名称。来自统计（2）手册页：

The following mask values are defined for the file mode component of
the st_mode field:

    S_ISUID     04000   set-user-ID bit
    S_ISGID     02000   set-group-ID bit (see below)
    S_ISVTX     01000   sticky bit (see below)

    S_IRWXU     00700   owner has read, write, and execute permission
    S_IRUSR     00400   owner has read permission
    S_IWUSR     00200   owner has write permission
    S_IXUSR     00100   owner has execute permission

    S_IRWXG     00070   group has read, write, and execute permission
    S_IRGRP     00040   group has read permission
    S_IWGRP     00020   group has write permission
    S_IXGRP     00010   group has execute permission

    S_IRWXO     00007   others (not in group) have read,  write,  and
                        execute permission
    S_IROTH     00004   others have read permission
    S_IWOTH     00002   others have write permission
    S_IXOTH     00001   others have execute permission

我可以看到它是和（用户的读取、写入和执行权限）S_IRWXU的组合，并且是和（用户的读取权限）的组合。对于写入和执行以及组和其他人也是如此。rwxuS_IRUSRRusr

该S部分可能以stat功能命名。

但那I部分又是什么意思呢？它是根据各种S_ISDIR（“是目录”）宏建模的吗？

VTX该部分来自什么S_ISVTX？我无法将此缩写与“粘性位”联系起来。

Answer 1

现在是历史时刻了，孩子们！ Stevens，“APUE”，第 4 章，第 10 节如此引用：

“S_ISVTX 位有一个有趣的历史......如果它被设置......程序文本的副本被保存在交换区域中......这导致程序下次更快地加载到内存......更高的版本Unix 将此称为保存的文本位，因此为常数 S_ISVTX。”