File

The xv6 file system provides data files, which are uninterpreted byte arrays, and directories, which contain named references to data files and other directories.

Paths that don’t begin with / are evaluated relative to the calling process’s current directory,

A file, called an inode, can have multiple names, called links. The link system call creates another file system name referring to the same inode as an existing file.

The file’s inode and the disk space holding its content are only freed when the file’s link count is zero and no file descriptors refer to it.

cd changes current process working directory. When shell running this cmd, it does not fork child and change dir. Instead, it change the current working directory of the shell itself. The reason behind is: if forking a child to do cd, we are changing the child process’s working directory, not our current shell process.