这应该是个内置命令,在shell里;bash shell或者其他shell
whereis mkdir
mkdir: /bin/mkdir /usr/share/man/man1/mkdir.1.gz /usr/share/man/man2/mkdir.2.gz /usr/share/man/man3p/mkdir.3p.gz /usr/share/man/man1p/mkdir.1p.gz
目录路径在
/bin/mkdir
$ which mkdir
/bin/mkdir
which mkdir