ncdu 最左边一列的符号是什么意思？

Question

操作系统：Kubuntu 16.04 和ncdu1.11 版。

当我跑

ncdu -x /

我得到

--- / --------------------------------------
.  97.1 GiB [##########] /home              
    4.6 GiB [          ] /usr
  718.8 MiB [          ] /lib
. 562.4 MiB [          ] /var
  177.8 MiB [          ] /opt
  143.2 MiB [          ] /boot
   12.7 MiB [          ] /bin
.  11.1 MiB [          ] /etc
   11.0 MiB [          ] /sbin
. 100.0 KiB [          ] /tmp
   36.0 KiB [          ] /mnt
.  16.0 KiB [          ] /media
!  16.0 KiB [          ] /lost+found
    4.0 KiB [          ] /lib64
e   4.0 KiB [          ] /srv
!   4.0 KiB [          ] /root
e   4.0 KiB [          ] /cdrom
@   0.0   B [          ]  initrd.img.old
@   0.0   B [          ]  initrd.img
@   0.0   B [          ]  vmlinuz.old
@   0.0   B [          ]  vmlinuz
>   0.0   B [          ] /sys
>   0.0   B [          ] /run
>   0.0   B [          ] /proc
>   0.0   B [          ] /dev

做什么.，!，e，@，和>是什么意思？man ncdu并且info ncdu没有关于这些符号含义的任何信息。

man du 也没有帮助。

Answer 1

在 中ncdu，按?显示帮助，然后2按 显示格式帮助。

这里是 ：

????ncdu help?????????????????1:Keys???2:Format???3:About???
?                                                          ?
?  X  [size] [graph] [file or directory]                   ?
?   The X is only present in the following cases:          ?
?                                                          ?
?   !  An error occured while reading this directory       ?
?   .  An error occured while reading a subdirectory       ?
?   <  File or directory is excluded from the statistics   ?
?   >  Directory was on an other filesystem                ?
?   @  This is not a file nor a dir (symlink, socket, ...) ?
?   H  Same file was already counted (hard link)           ?
?   e  Empty directory                                     ?
?                                                          ?
?                                         Press q to close ?
????????????????????????????????????????????????????????????