为什么touch命令也会改变ctime？

Question

# stat main.c
Access: 2023-12-14 23:43:08.299761676 +0800
Modify: 2023-12-14 23:43:08.274761678 +0800
Change: 2023-12-14 23:43:08.274761678 +0800
 Birth: -

# touch main.c
# stat main.c (all the three times changed.)
Access: 2023-12-14 23:43:37.956758479 +0800
Modify: 2023-12-14 23:43:37.893758486 +0800
Change: 2023-12-14 23:43:37.893758486 +0800
 Birth: -

# for -a option,atime and ctime will change.
# for -m option,atime mtime,ctime all three will change.

我很困惑为什么 touch 命令也会改变 ctime？

touch changes the access and/or modification timestamps of the specified files.
(As you can see,only atime and mtime are mentioned.)

# options:
-a. Change the access timestamp only.
-m. Change the modification timestamp only.

# https://www.gnu.org/software/coreutils/manual/html_node/touch-invocation.html

所以我很困惑。

触摸命令之后，main.c 的内容与之前相同。

但是mtime已经改变了。（我无法理解。）

Answer 1

touch被指定为改变文件访问和修改时间；更改更改时间是更改文件元数据的副作用，而 touch 对此没有任何控制权（另请参阅 touch 使用的 futimens() 和 utimensat() 函数）。