sudo apt-get install --reinstall base-files

pi@raspberrypi ~ $ sudo apt-get install --reinstall base-files
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
  base-files
1 upgraded, 0 newly installed, 0 to remove and 60 not upgraded.
1 not fully installed or removed.
Need to get 66.9 kB of archives.
After this operation, 203 kB disk space will be freed.
Get:1 http://mirrordirector.raspbian.org/raspbian/ wheezy/main base-files armhf 7.1wheezy9+rpi1 [66.9 kB]
Fetched 66.9 kB in 0s (137 kB/s)
(Reading database ... 80136 files and directories currently installed.)
Preparing to replace base-files 7.1wheezy8+rpi1 (using .../base-files_7.1wheezy9+rpi1_armhf.deb) ...
Unpacking replacement base-files ...
dpkg: error processing /var/cache/apt/archives/base-files_7.1wheezy9+rpi1_armhf.deb (--unpack):
 unable to stat `./usr/share/doc/base-files' (which I was about to install): Input/output error
/var/lib/dpkg/info/base-files.postinst: 1: /var/lib/dpkg/info/base-files.postinst: ms: not found
/var/lib/dpkg/info/base-files.postinst: 2: /var/lib/dpkg/info/base-files.postinst: f: not found
/var/lib/dpkg/info/base-files.postinst: 2: /var/lib/dpkg/info/base-files.postinst: t: not found
/var/lib/dpkg/info/base-files.postinst: 3: /var/lib/dpkg/info/base-files.postinst: echdatietc/to: not found
/var/lib/dpkg/info/base-files.postinst: 4: /var/lib/dpkg/info/base-files.postinst: Syntax error: "fi" unexpected
dpkg: error while cleaning up:
 subprocess installed post-installation script returned error exit status 2
Errors were encountered while processing:
 /var/cache/apt/archives/base-files_7.1wheezy9+rpi1_armhf.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)