CentOS – How to Install Man Pages

Starting from @derobert's answer, I worked my way to getting exactly the current version of all packages to reinstall.

Short version:

sudo dpkg -l | grep '^ii ' | sed 's/  */\t/g' |cut -f 2,3 | sed 's/\t/=/' | xargs apt-get install --reinstall -y --ignore-missing

Explained:

The key is actually specifying the required version of each package.

The general command is:

apt-get install --reinstall <package>=<version>

Breaking down the long command line:

$ dpkg -l

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                                        Version                            Architecture Description
+++-===========================================================-==================================-============-========================================================================
ii  adduser                                                     3.113+nmu3                         all          add and remove users and groups
ii  apt                                                         0.9.7.8+rpi1                       armhf        commandline package manager
ii  apt-utils                                                   0.9.7.8+rpi1                       armhf        package managment related utility programs
ii  aptitude-common                                             0.6.8.2-1                          all          architecture indepedent files for the aptitude package manager
ii  atmel-firmware                                              1.3-4                              all          Firmware for Atmel at76c50x wireless networking chips.

$ dpkg -l | grep '^ii '

...gets rid of the header lines and a few packages with status 'hold' (marked as hi instead of ii)

$ dpkg -l | grep '^ii ' | sed 's/  */\t/g'

... converts any number of spaces to a single TAB character, preparing the ground for cut.
(Btw: why, oh why, doesn't sed support x+ regex for "character x, one or more times"? It can be emulated with xx* - meaning 'x' once followed by 'x' zero or more times)

The output looks like this:

ii      adduser 3.113+nmu3      all     add     and     remove  users   and     groups
ii      apt     0.9.7.8+rpi1    armhf   commandline     package manager
ii      apt-utils       0.9.7.8+rpi1    armhf   package managment       related utility programs
ii      aptitude-common 0.6.8.2-1       all     architecture    indepedent      files   for     the     aptitude        package manager
ii      atmel-firmware  1.3-4   all     Firmware        for     Atmel   at76c50x        wireless        networking      chips.

Next:

$ dpkg -l | grep '^ii ' | sed 's/  */\t/g' | cut -f 2,3 | sed 's/\t/=/'

...gets the name and version of each package (the 2nd and 3rd fields), and replaces the tab that separates them with an '='

adduser=3.113+nmu3
apt=0.9.7.8+rpi1
apt-utils=0.9.7.8+rpi1
aptitude-common=0.6.8.2-1
atmel-firmware=1.3-4

Finally, pipe each of the above to apt-get as a long list of arguments using xargs.

Notice the parameter --ignore-missing - this command is run as 'best effort' - I don't want the updating to stop because some packages are not available to reinstall (those will stay unmodified)

$ dpkg -l | grep '^ii ' | sed 's/  */\t/g' |cut -f 2,3 | sed 's/\t/=/' | xargs apt-get install --reinstall --ignore-missing

While testing, I also added a --dry-run argument to apt-get.

For quickly getting help on a Bash builtin, use help:

help read

is what you want.

For man-page-like formatting, use

help -m read

or, even better,

help -m read | less

If you still insist on looking for it in the man page, I find what quickly gets me to a command's explanation is

/^\s*read [[]

This works because when a command is first explained, its name is indented slightly from the start of the line. In the particular case of read, this takes a little browsing before you get to the actual read documentation because (for obvious reasons) the word "read" is repeated a lot throughout the man page. The [[] means to match a [ which usually precedes optional parameters. (I usually leave out /^\s* and simply do /<built-in command> [[])

Another alternative

If you don't mind the format change, you can convert your man page to a DVI or PDF file:

man -T dvi bash >bash.dvi

or

man -T ps bash | ps2pdf - bash.pdf # Requires the Ghostscript suite for ps2pdf

Of course, given a DVI or PDF document, you can then do a text search easily.