



















               [1mman-db - the database cached manual pager suite[0m


                  [4mGraeme[24m [4mW.[24m [4mWilford[24m [4m<eep2gw@ee.surrey.ac.uk>[0m
                      [4mColin[24m [4mWatson[24m [4m<cjwatson@debian.org>[0m






    This  document  describes  the setup, maintenance and use of a generic
    online manual page system with special reference to the man-db package
    and its advanced features.




































[1mman-db                              v2.8.7                      April 19, 2021[0m


[1mUNIX [22mis a registered trademark of the X/Open Company, Ltd.
NFS is a registered trademark of Sun Microsystems, Inc.
PostScript is a registered trademark of Adobe in the United States.

The general conventions used throughout this manual include

 +o file names and paths in [4mitalic[24m, e.g.  [4m/usr/share/man[24m.
 +o variable  strings  (usually  path  components)  enclosed  within  <> and in
   [4mitalic[24m, eg.  [4m<sec>[24m,
 +o program names in [1mbold[22m, eg.  [1mman[22m.                  _____       ____________
 +o commands that can be typed at a shell prompt in a |_b_o_x_|_, eg.  |_m_a_n__f_o_o_b_a_r_|_.
 +o environment variables denoted as follows: $[1mENV_VAR[0m























Copyright (C) 1995 Graeme W. Wilford
Copyright (C) 2001, 2002, 2003, 2007 Colin Watson

Permission is granted to make and distribute verbatim copies  of  this  manual
provided  the copyright notice and this permission notice are preserved on all
copies.

Permission is granted to copy and distribute modified versions of this  manual
under  the conditions for verbatim copying, provided that the entire resulting
derived work is distributed under the terms of a notice identical to this one.

Permission is granted to copy and distribute translations of this manual  into
another  language,  under  the  above conditions for modified versions, except
that this permission notice may be stated in a  translation  approved  by  the
copyright holder.













[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m1.  Introduction[0m

[1m1.1.  man-db[0m

man-db  is a package that is designed to provide users with online information
in a fast and friendly manner while at the same time offering  flexibility  to
the system administrator.

It is made up of several user programs:
         [1m+o man       [22m- an interface to the on-line reference manuals
         [1m+o whatis    [22m- search the manual page names
         [1m+o apropos   [22m- search the manual page names and descriptions
         [1m+o manpath   [22m- determine search path for manual pages
         [1m+o lexgrog   [22m- directly read header information in manual pages
several maintenance programs:
         [1m+o mandb     [22m- create or update the manual page index caches
         [1m+o catman    [22m- create or update the pre-formatted manual pages
and a special pre-formatter that knows about compressed manual pages:
         [1m+o zsoelim   [22m- satisfy .so requests in roff input


In addition to these compiled programs, there are two shell scripts, [1mmkcatdirs[0m
and [1mcheckman [22min the [4mtools[24m subdirectory.  These scripts aid the creation of cat
directories and check for duplicated manual pages, respectively.

The  following  manual pages are provided with this package to explain correct
format and usage.  [1mman[22m(1), [1mwhatis[22m(1), [1mapropos[22m(1), [1mmanpath[22m(1), [1mlexgrog[22m(1), [1mman-[0m
[1mpath[22m(5), [1mmandb[22m(8), [1mcatman[22m(8) and [1mzsoelim[22m(1).

[1m1.1.1.  The concept[0m

man-db  originally started out life as program suite man-1.1B, written by John
W.  Eaton <jwe@che.utexas.edu> and maintained by Rik Faith  <faith@cs.unc.edu>
to  which  support proposed by the newly formed FSSTND committee regarding cat
directories was added.

Since  then,  man-db's most innovative feature: the database cache scheme1 has
been significantly developed. The basic idea was to reduce manual page  search
times  to  a  minimum.  The  following piece of text is included from the man-
db-2.2 distribution:

    The theory: If you go to a library to take a book out, what do you do?

    a) Go and look where it might be on  a  micro-fiche/terminal,  take  a
    look  where it is supposed to be on the shelf, and then go look at the
    new arrivals if it's not where it's supposed to be?

    OR
____________________
   1 originally conceived after observing the actions of the Perl-based manual
pager suite, man-pl written by Tom Christiansen <tchrist@convex.com>




                                       [1m1[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


    b) Start at one end of the ground floor, look  along  every  bookshelf
    until  you've completed that floor, then go up a level and start again
    until you've found what you're looking for?


Since then the database [1mindex [22mscheme has evolved greatly.  Every  manual  page
and  stray  cat  page  on  the system is registered in an [1mindex [22mdatabase cache
which stores various details about the file including the timestamp, the loca-
tion and the whatis2 information.  This information is kept up to date by reg-
ular runs of [1mmandb[22m.  In some configurations  [1mman  [22malso  looks  for  filesystem
changes  each time it is invoked and helps to keep the database cache current,
but this imposes a penalty on manual page search times.

[1m1.2.  The manual page system[0m

The simplest manual page system will have  a  single  manual  page  hierarchy.
This will typically be

     [4m/usr/share/man[0m

beneath  which will be several subdirectories of the form [4mman<sec>[24m where [4m<sec>[0m
is [1m1[22m, [1m2[22m, [1m3[22m, [1m4[22m, [1m5[22m, [1m6[22m, [1m7 [22mor [1m8[22m.  These are referred to as [4msections[24m of the manual.
Others may exist and they are not restricted to single character names. eg.

     [4m/usr/share/man/manfoo[0m

is a valid section subdirectory.  Other common sections include [1m9[22m, [1mn[22m, [1ml[22m, [1mp [22mand
[1mo[22m.

Within these section subdirectories reside the manual pages themselves.  Their
filenames follow the pattern

     [4m/usr/share/man/man<sec>/<name>.<sec><ext>[0m

where in most cases [4m<ext>[24m is an empty string.  An example is manual page [1mcp[0m

     [4m/usr/share/man/man1/cp.1[0m

which resides in [4msection[24m [1m1 [22mand has no special [4mextension[24m.

[1m1.3.  Sections of the manual[0m

The  manual  is  split up into sections to ease access and to cater for manual
pages that share the same name.  It is common for a program  and  function  to
share  the  same  name.  [1mkill [22mis a good example.  This is both a program which
can be used to send a process a signal and an operating system call with simi-
lar  functionality.   Their manual pages are stored under sections [1m1 [22mand [1m2 [22mre-
spectively.  Thus, sections are used to separate out the program manual  pages
from  the  function manual pages and so on.  The table below shows the [4msection[0m
____________________
   2 one line description of the manual page




                                       [1m2[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


numbers of the manual followed by the types of pages they contain.


       +--------+------------------------------------------------------+
       |Section |                   Section contents                   |
       +--------+------------------------------------------------------+
       |   1    | user executable programs or shell commands           |
       |   2    | system calls (functions provided by the kernel)      |
       |   3    | library calls (functions within system libraries)    |
       |   4    | special files (usually found in [4m/dev[24m)                |
       |   5    | file formats and conventions eg. [4m/etc/passwd[24m         |
       |   6    | games                                                |
       |   7    | macro packages and conventions eg. [1mman[22m(7), [1mgroff[22m(7). |
       |   8    | system administration commands                       |
       |   9    | kernel routines [Non-standard]                       |
       |   n    | new [obsolete]                                       |
       |   l    | local [obsolete]                                     |
       |   p    | public [obsolete]                                    |
       |   o    | old [obsolete]                                       |
       +--------+------------------------------------------------------+


[1m1.4.  The format of manual pages[0m

The format in which manual pages are stored is [1mNROFF[22m/[1mTROFF [22mor  more  generally
ROFF.   This  is a typesetter style language3 which requires formatting before
being viewed.  In fact some manual pages require pre-format processing to cor-
rectly format tables or equations.

If  the page is to be viewed on screen in a text environment, [1mNROFF [22mis used as
the primary formatter. If the page is to be printed or displayed in a  graphi-
cal  environment,  [1mTROFF  [22mis  used. Traditionally, [1mTROFF [22mformatted files for a
[1mC/A/T [22m(Computer aided Typesetter) which is now obsolete.

The [1mGNU [22mROFF ([1mGROFF[22m4) suite of programs offer a choice of output types includ-
ing [1mX[22m, [1mdvi [22mand [1mpostscript[22m.  When configuring man-db, the preference is to  use
[1mGROFF [22mrather than [1mTROFF[22m.

[1m1.5.  Arguments to configure[0m

To  allow  the configuration program, [1mconfigure[22m, to be non-interactive, it can
be passed various options to alter the default  settings.   Generic  [1mconfigure[0m
options  are  discussed  in  [4mdocs/INSTALL[24m.   Options  that are specific to the
man-db package are described below.

--enable-cache-owner[=ARG]
     By default, system-wide cache files will be owned by user man.  Use  this
____________________
   3 similar in some aspects to [1mTeX[0m
   4 Written by James Clark <jjc@jclark.com> and now maintained by Ted Harding
<ted.harding@nessie.mcc.ac.uk> and Werner Lemberg <wl@gnu.org>




                                       [1m3[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


     option with an argument to change the cache file owner.

--disable-cache-owner
     Use  this option to leave the ownership of system-wide cache files uncon-
     strained.  Users will be allowed to modify them.

--disable-setuid
     By default, [1mman [22mwill be installed as a setuid program to  the  user  that
     owns  the  system-wide  cache files.  Use this option to install [1mman [22mas a
     non-setuid program instead.

--enable-mandirs=OS
     By default, man-db supports manual page directories  in  any  of  several
     layouts  used by free and proprietary versions of [1mUNIX[22m.  However, in cer-
     tain cases, this can cause man-db to find the wrong page by mistake,  es-
     pecially  when the names of some manual pages on the system contain peri-
     ods.  Use this option with an argument of GNU, HPUX,  IRIX,  Solaris,  or
     BSD  (or more than one of these, separated by commas) to support only the
     layouts typically used on each of those systems.  Note that man-db is not
     currently capable of writing cat pages in the proper BSD layout.

--with-device=DEVICE
     Use this flag to alter the default output device used by [1mNROFF[22m. DEVICE is
     passed to [1mNROFF [22mwith the -T option.  [1mconfigure [22mwill test that [1mNROFF  [22mwill
     run with the supplied device argument.

--with-db=LIBRARY
     configure  will  look for database interface libraries in the order gdbm,
     Berkeley DB and finally ndbm and will #define appropriate variables rela-
     tive to the first one found.  To override the built-in order on platforms
     having a choice of interface library, use this option  to  specify  which
     library to use.

--enable-automatic-create
     If  this  flag is used, [1mman [22mwill automatically create index databases for
     users' private manual page hierarchies.

--disable-automatic-update
     Normally, [1mman [22mwill update entries in index databases if  it  finds  newly
     installed  manual  pages (if the [1m--update [22mflag is used) or delete entries
     if manual pages are removed.  This flag suppresses this behaviour.

--disable-cats
     Normally, [1mman [22mwill automatically try to create cat files corresponding to
     manual  files  when a manual page is read.  This flag suppresses this be-
     haviour.

--disable-manual
     Don't build or install the man-db manual.  This may be useful when cross-
     compiling, or to reduce the installation size.





                                       [1m4[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m2.  The specifics of Sections[0m

[1m2.1.  Package specific manual page sections[0m

The  use  of  package specific manual page sections is discouraged as packages
large enough to warrant their own section probably contain manual  pages  that
span other sections.  An example might be package [1mfoo [22mthat has its own section

     [4m/usr/share/man/manfoo[0m

which  contains  manual pages describing its programs, the library routines it
offers and the format of several of  its  configuration  files.   These  pages
would  normally be allocated to sections [1m1[22m, [1m3 [22mand [1m5 [22mrespectively and thus com-
bining them all under section [1mfoo [22mis misleading.  Subtle problems  will  arise
if  there  are  any  base  name-space clashes with standard manual pages, e.g.
[1mexit[22m(3), [1mexit[22m(foo) and the order in which they should be shown.

There are two standard solutions to this problem.

 (1)   Create a separate manual page hierarchy for the package's manual  pages
       such as

           [4m/usr/local/packages/foo/man[0m


 (2)   Install  the  pages in their relevant sections, with a unique extension
       appended to the filename such that

           [4m/usr/share/man/manfoo/exit.foo[0m

       would instead be installed as

           [4m/usr/share/man/man1/exit.1foo[0m


Only (2) offers a complete solution to manual page ordering problems  and  al-
lows users to access the desired page directly.

[1m2.2.  Selecting a section type[0m

[1m2.2.1.  Specifying a section[0m

This is done via use of the section argument to man
     ____________
     |_m_a_n__1__e_x_i_t_|_

will  look  for [4mexit.1*[24m in section [1m1 [22mof the manual.  If [4mexit.1[24m exists, it will
be displayed in preference to [4mexit.1foo[0m
     _______________
     |_m_a_n__1_f_o_o__e_x_i_t_|_

will look for [4mexit.1foo*[24m in section [1m1 [22mof the manual.  The asterisk (*)  repre-
sents a wild-card of any type or length, including length zero.


                                       [1m5[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


For  an  argument to be interpreted as a section name rather than a page name,
it must either begin with a digit, or be  included  in  the  standard  section
list.   The default section list is defined in [4minclude/manconfig.h[24m to be [1m1[22m, [1mn[22m,
[1ml[22m, [1m8[22m, [1m3[22m, [1m2[22m, [1m5[22m, [1m4[22m, [1m9[22m, [1m6 [22mand [1m7[22m.  This should be modified in order and content to
meet  the  local conventions.  It may be altered at run-time using the [1mSECTION[0m
directive in the man-db configuration file.

Every subdirectory section name in the entire system must be in the list,  in-
cluding  sections found in imported manual page hierarchies.  It is not neces-
sary to list sections with extensions unless a special ordering for those  ex-
tensions  is desired.  The order is important because in normal operation, [1mman[0m
will only display the first manual page it finds that meets the search  crite-
ria.  Using the [1m--all [22margument will cause [1mman [22mto attempt to display all manual
pages that meet the criteria. See [1mman[22m(1) for further information.

Having an excess of sections listed will not slow [1mman [22mdown.

[1m2.2.2.  Specifying an extension[0m

If the section is unknown, but the package extension is, it is possible to use
the extension argument
     _________________
     |_m_a_n__-_e__f_o_o__e_x_i_t_|_

to search in all sections for manual pages named [4mexit[24m from package [4mfoo[24m.






























                                       [1m6[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m3.  Filesystem structure[0m

[1m3.1.  Manual page hierarchies[0m

It  is  often common for manual page systems to have more than one manual page
hierarchy.  Indeed one of the systems I use has the following globally  acces-
sible hierarchies

     [4m/usr/man[0m
     [4m/usr/local/man[0m
     [4m/usr/local/tex/man[0m
     [4m/usr/local/pbm/man[0m
     [4m/usr/X11R6/man[0m
     [4m/usr/openwin/man[0m
     [4m/usr/local/packages/pvm/man[0m

A  full  system $[1mMANPATH [22mwould be a colon separated list of these directories.
The order is important, and is observed by man-db's  search  algorithms.   The
order  is  very  much  related  to  the user's $[1mPATH [22menvironment variable, and
should be set on a per user basis, or not set  at  all.   If  a  user's  $[1mPATH[0m
causes

     [4m/usr/local/packages/bin/foobar[0m

to be executed in preference to

     [4m/usr/bin/foobar[24m,

it is essential that
     ____________
     |_m_a_n__f_o_o_b_a_r_|_

displays the manual page located within

     [4m/usr/local/packages/man[0m

rather than within

     [4m/usr/share/man[0m

To  ensure  correct order, the program [1mmanpath [22mmay be used to set the $[1mMANPATH[0m
environment variable.  See [1mmanpath[22m(1) and [1mmanpath[22m(5) for details.

[1m3.2.  Setting the MANPATH[0m

If using a Bourne style login shell such as [1mbash[22m, [1mksh[22m, or [1mzsh[22m, the commands

     export MANPATH
     MANPATH=`manpath -q`

can be added to [1m$HOME[4m[22m/.profile[0m




                                       [1m7[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


If using a C style login shell such as [1mcsh [22mor [1mtcsh[22m, the commands

     setenv MANPATH `manpath -q`

can be added to [1m$HOME[4m[22m/.login[0m

N.B.  $[1mPATH [22mmust be set prior to using [1mmanpath[22m.  The setting  of  $[1mMANPATH  [22mis
actually  unnecessary  as  the man-db utilities will dynamically determine the
manpath if $[1mMANPATH [22mis unset.

[1m3.3.  Determination of the internal manpath[0m

All man-db utilities, [1mmanpath [22mincluded, will use the user's $[1mMANPATH  [22menviron-
ment variable if set and not equal to "".  Otherwise the user's $[1mPATH [22menviron-
ment variable is queried.  If this is unset or is set to  "",  the  determined
manpath will simply be any

     [1mMANDATORY_MANPATH[0m

elements defined in the man-db config file.

Assuming  that a $[1mPATH [22mexists, each path element it contains is scanned for in
the config file.  If found, the corresponding manpath element is  appended  to
the  internal manpath.  However, if the element is not mentioned in the config
file, a man directory relative to  it  will  be  sought.   The  subdirectories
[4m../man[24m, [4mman[24m, [4m../share/man[24m, or [4mshare/man[24m relative to the path component are ap-
pended to the internal manpath if they exist.  Finally, the  internal  manpath
is  stripped  of  duplicate paths before being processed by the [1mNLS [22mand `Other
OS' routines.  These may add to or modify the separate  path  elements  giving
priority to [1mNLS [22mmanual pages or add OS-relative manpaths.

[1m3.4.  Other OS's manual pages[0m

It  is common to have collections of heterogeneous computer systems linked to-
gether in a network.  In some circumstances5 it is advantageous to be able  to
access  the  manual  pages  of  these other systems directly from your system.
This feature is known as alternate system support.  The accepted way to  setup
this  support  is to NFS mount the respective systems' manual page hierarchies
under the native manual page hierarchies.  An example:









____________________
   5 writing portable software instantly comes to mind





                                       [1m8[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


                      +--------+-----------------------+
                      |System  | Manual page hierarchy |
                      +--------+-----------------------+
                      |<local> | /usr/share/man        |
                      |newOS   | /usr/share/man/newOS  |
                      |userix  | /usr/share/man/userix |
                      |<local> | /usr/local/man        |
                      |newOS   | /usr/local/man/newOS  |
                      |userix  | /usr/local/man/userix |
                      +--------+-----------------------+

Rather than have multiple NFS mounts from a single machine, this may be accom-
plished by NFS mounting

     [4m<other-sys>:/usr[0m

somewhere on the local system and using symbolic links within the manual hier-
archies.  To access these [4malternate[24m [4msystems[24m using [1mman [22muse the [1m-m [22mor  [1m--systems[0m
option, eg.
     ___________________________________________
     |_m_a_n__-_-_a_l_l__-_-_s_y_s_t_e_m_s__u_s_e_r_i_x_:_n_e_w_O_S__5__p_a_s_s_w_d_|_

would  provide  manual  pages  showing the structure of [4m/etc/passwd[24m on systems
[1muserix [22mand [1mnewOS [22min that order.  A manual page would [4mnot[24m  be  displayed  about
the local systems conventions.  Please read the relevant man-db utility's man-
ual page for further and more specific information.

[1m3.5.  NLS manual pages[0m

NLS manual pages should be installed in NLS subdirectories of a standard  man-
ual  page  hierarchy.   The  subdirectory names should be made up of language,
territory, and character set components as necessary to specify the locale  of
the manual page.

The  character set component describes the encoding of the manual page itself,
and not the encoding in use by the user; a manual  page  installed  under  the
[1mfr.UTF-8  [22msubdirectory  will be used in the [1mfr_FR.ISO-8859-1 [22mlocale as well as
[1mfr_FR.UTF-8[22m, and converted between encodings as necessary.   If  no  character
set  is  specified  in  the  subdirectory  name, man-db will attempt to detect
whether each page is encoded using UTF-8 or a legacy character set appropriate
for  the  language.  Accordingly, the recommended scheme for installing manual
pages is to encode them in UTF-8 (or, if that is not practical, in the  legacy
character  set) and install them in directories [4mwithout[24m a character set compo-
nent in their names.

The territory should normally be omitted unless it is  necessary  to  describe
the  manual  page  text.   For example, Brazilian Portuguese is quite distinct
from Portuguese and so should be installed under the [1mpt_BR [22msubdirectory, but a
single German manual page will typically suffice in Austria as well as in Ger-
many and so should be installed under the [1mde [22msubdirectory.





                                       [1m9[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


The following table gives some examples.


 +---------+-------------+-----------------+---------------------------------+
 |Language | Territory   | Character Set   | Directory                       |
 +---------+-------------+-----------------+---------------------------------+
 |French   | any         | UTF-8 or        | /usr/share/man/fr               |
 |         |             | ISO-8859-1      |                                 |
 |French   | Canada      | ISO 8859-1      | /usr/share/man/fr_CA            |
 |French   | any         | UTF-8           | /usr/share/man/fr.UTF-8         |
 |German   | Germany     | UTF-8           | /usr/share/man/de_DE.UTF-8      |
 |German   | Switzerland | ISO 8859-1      | /usr/share/man/de_CH.ISO-8859-1 |
 |Japanese | Japan       | UTF-8 or EUC-JP | /usr/share/man/ja_JP            |
 |Japanese | Japan       | EUC-JP          | /usr/share/man/ja_JP.EUC-JP     |
 |Japanese | any         | UTF-8           | /usr/share/man/ja.UTF-8         |
 +---------+-------------+-----------------+---------------------------------+

On  systems  supporting  UTF-8, it is recommended that all manual pages be en-
coded using UTF-8 where possible, in order to simplify the task of  editing  a
variety of pages without reconfiguring editors and terminals and the like.

Each  of  these  directories  are  then interpreted as manual page hierarchies
themselves and may contain the usual section subdirectories.   Access  to  NLS
manual  pages  is  achieved via use of the [1msetlocale[22m(3) function which queries
user environment variables to determine the current locale.  Internally to the
man-db  utilities,  this locale string is appended to each manpath element and
the resultant NLS manpath element is searched before the standard manpath ele-
ment.   In  this way, an NLS manual page that matches the search criteria will
be shown before or in place of the standard American English page.

If a user's $[1mMANPATH [22mconsists of or is determined as

     [4m/usr/local/man:/usr/share/man:/usr/X11R6/man[0m

and their locale is set to [1mde_DE[22m, the command
     _________________________________
     |_m_a_n__-_-_s_y_s_t_e_m_s__u_s_e_r_i_x_:_m_a_n__f_o_o_b_a_r_|_

would produce the following internal man-db manpath elements


     [4m/usr/local/man/userix/de_DE[0m
     [4m/usr/local/man/userix/de[0m
     [4m/usr/local/man/userix[0m
     [4m/usr/share/man/userix/de_DE[0m
     [4m/usr/share/man/userix/de[0m
     [4m/usr/share/man/userix[0m
     [4m/usr/X11R6/man/userix/de_DE[0m
     [4m/usr/X11R6/man/userix/de[0m
     [4m/usr/X11R6/man/userix[0m
     [4m/usr/local/man/de_DE[0m
     [4m/usr/local/man/de[0m



                                      [1m10[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


     [4m/usr/local/man[0m
     [4m/usr/share/man/de_DE[0m
     [4m/usr/share/man/de[0m
     [4m/usr/share/man[0m
     [4m/usr/X11R6/man/de_DE[0m
     [4m/usr/X11R6/man/de[0m
     [4m/usr/X11R6/man[0m

[1mfoobar [22mwould be searched for in the order of manual page  hierarchies  listed.
Additional  directories  corresponding  to  manual  pages encoded in different
character sets would be used if present.

[1m3.5.1.  ISO 8859-1 (latin1) manual pages[0m

By default [1mNROFF [22mwill format manual pages into a form  suitable  for  a  type-
writer  style device, e.g. a terminal screen. [1mGNU NROFF [22mis capable6 of format-
ting ROFF into a form suitable for 8-bit latin1 capable output devices. To en-
able output for such a device, give the option

--with-device=DEVICE

to [1mconfigure [22mwhere DEVICE is the suitable and supported output format, in this
case [1mlatin1[22m.

[1m3.5.2.  Displaying non-ASCII characters on a Linux virtual terminal[0m

To view non-ASCII characters at the Linux console, you must have  one  of  the
kbd7  and console-tools packages installed.  If your system does not come with
suitable configuration already, then please see the documentation in  the  kbd
or  console-tools package for details on how to configure the console for your
locale.  On modern systems, the best choice is likely to be to use  the  UTF-8
encoding  with  a font suitable for your language.  Make sure that your locale
environment variables match the encoding displayed by the console.   For  dis-
play  under the "X Window System", a suitable 8-bit-clean terminal emulator is
required.

[1m3.5.3.  Viewing ASCII pages formatted for latin1 output device[0m

When formatting an ASCII manual page for a latin1  output  device,  [1mGNU  NROFF[0m
will  take advantage of the extra characters available and will always produce
a text page containing some latin1 (8-bit) symbols.  The table8  below,  taken
from [1mman[22m(1), illustrates the differences.



____________________
   6 see [1mnroff[22m(5) for the output device formats available with your [1mNROFF[0m
   7 written and maintained by Andries Brouwer <aeb@cwi.nl>.
   8 The ISO 8859-1 and ASCII columns of this table will be identical if  this
manual  was  formatted for an ASCII based typewriter display, i.e. using [1mNROFF[0m
in its native mode.




                                      [1m11[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


              +--------------------+-------+------------+-------+
              |Description         | Octal | ISO 8859-1 | ASCII |
              +--------------------+-------+------------+-------+
              |continuation hyphen |  255  |            |   -   |
              |bullet (middle dot) |  267  |     +o      |   o   |
              |acute accent        |  264  |     '      |   '   |
              |multiplication sign |  327  |     x      |   x   |
              +--------------------+-------+------------+-------+

To display such symbols on a 7 bit terminal or terminal emulator, they must be
translated back into standard ASCII.  The [1m-7 [22moption with [1mman [22mwill enable  this
simple reverse translation.

This option may be useful if your site has both 7 and 8-bit capable output de-
vices and nroff is using the latin1 output device to format manual pages.

[1m3.6.  Cat pages[0m

It has become standard practice to store the formatted manual pages on disk so
that  subsequent  requests for the manual page do not have to involve the for-
matting process.  These pre-formatted manual pages are  known  as  [4mcat[24m  pages.
Although  cat pages require additional disk storage requirements, they provide
a substantial speed increase and their use is recommended.

The automatic support for storing and using cat pages is brought about by sim-
ply creating suitable directories for them.

[1m3.7.  Cat page hierarchies[0m

Traditionally,  cat pages were stored under the same manual hierarchy as their
source manual pages, in [4mcat<sec>[24m subdirectories rather  than  [4mman<sec>[24m.   This
situation is rather limiting in several situations:



 +o When it is advantageous to mount [4m/usr[24m as a read-only filesystem.  Cat pages
   cannot be supported in this situation without use of symbolic links to var-
   ious other areas of the filesystem.  This situation is a greater problem if
   the media itself is read-only, such as CD-ROM.
 +o When NFS mounting alternate OS's manual page  hierarchies.   The  alternate
   system  may be under someone else's control and they may not want cat pages
   stored on their system.  In fact, it is usually a good idea to  export  the
   manual page filesystems read-only, or import them that way.  It is possible
   to avoid the problems, this time with even more  symbolic  links  that  may
   need periodic updating.
 +o If  there is a mixture of normal cat files and stray cats9, it is very dif-
   ficult to periodically [4mtrim[24m the cat space disk usage by removing seldom ac-
   cessed cat files.

____________________
   9 cat files that have no source manual page, i.e. they cannot be recreated.




                                      [1m12[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


To avoid all of these problems simultaneously, it was decided to support local
cat page directory caches.

[1m3.8.  Local cat page directory caches[0m

Any location for cat page hierarchy may be specified in the man-db  configura-
tion  file.   The  location  of the database cache associated with each manual
page hierarchy will always be at the root of the cat page hierarchy.   By  de-
fault, the cat page hierarchy shadows the manual page hierarchy.  The [1mFHS [22mpro-
poses [4m/var/cache/man[24m as the location for such directories, although man-db al-
lows  any directory hierarchy to be used.  The [1mFHS [22mpath transformation rule is
as follows:

     [4m/usr/<hierarchy>/share/man/<locale>/man<sec>/page.<sec><ext>[0m

should be formatted into the cat file

     [4m/var/cache/man/<hierarchy>/<locale>/cat<sec>/page.<sec><ext>[0m

where the [4m<locale>[24m directory component may be missing  and  [4m<ext>[24m  may  be  an
empty string.

The suggestion is that stray cats are located in the traditional hierarchy un-
der [4m/usr[24m whereas re-creatable cat pages are stored under  the  local  writable
hierarchy  [4m/var/cache/man.[24m  [1mman [22mfollows strict rules in determining which file
is displayed.

As an example, the following route is taken if all three files exist.

 (1)   Check relative modification time stamps of the manual file and the tra-
       ditional  cat  file.   If the cat file is up to date (has an equal time
       stamp), display it.

 (2)   The traditional cat file is out of date.  Check relative time stamps of
       the  manual  file and the alternate cat file.  If the cat file is up to
       date, display it.

 (3)   The alternate cat file is out of date.  Format the manual file and dis-
       play  the  result  in  the foreground, while updating the alternate cat
       file in the background.

When a cat file is created, its time stamp is set to that of the corresponding
manual  file.   Manual files are often stored in [1mtar [22marchives, and time stamps
may be preserved when these archives are unpacked.   Simply  checking  whether
the  cat file is newer would sometimes cause [1mman [22mto display an out-of-date cat
file in this case, when it should have reformatted the manual file instead.









                                      [1m13[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m4.  Compression[0m

[1m4.1.  Compressed manual pages[0m

It is possible to maintain a system of compressed manual pages.  This  imposes
a  small  overhead on the formatting process, but is nevertheless usually rea-
sonable in order to avoid unnecessary consumption of disk space.

Presently, the compression extension/decompressor pairs must be known at  com-
pile  time  although any number may be defined and used.  The following struc-
ture is predefined in man-db:


                          +----------+--------------+
                          |Extension | Decompressor |
                          +----------+--------------+
                          |gz        | gzip -dc     |
                          |z         | gzip -dc     |
                          |Z         | compress -dc |
                          +----------+--------------+

It is a relatively easy operation to include further pairs in this  structure.
See [4minclude/comp_src.h[24m for details and an example.

Support  for  compressed manual pages is compiled into the man-db utilities by
default.  To completely disable this support, edit [4mconfig.h[24m  and  comment  out
the following line

#define COMP_SRC 1

This  will enable a minor speed increase, but note that support for stray cats
with any compression extension other than the default will also be disabled.

[1m4.2.  Compressed cat pages[0m

man-db compresses cat files by default.  During configuration, [1mconfigure  [22mwill
try  to  find  [1mgzip  [22mand, if found, all cat files produced by [1mman [22mwill be com-
pressed with

     [1mgzip -7c[0m

and have a [1m.gz [22mextension appended.  If [1mgzip [22mis not found,

     [1mcompress -c[0m

is used as the compressor and the extension [1m.Z [22mis appended.

To store cat files in an uncompressed state and to disable  compressed  exten-
sion processing completely, edit [4mconfig.h[24m and comment out the following line

#define COMP_CAT 1




                                      [1m14[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m4.2.1.  Stray cats[0m

Normally, [1mman [22mwill only look for cat files with the default compression exten-
sion.  The default compression extension is dependent on the default  compres-
sor and may be an empty string if the support for compressed cats is disabled.

It is possible for a system to be supplied with stray cat files located in the
traditional cat page hierarchy.  To make matters worse, they may have compres-
sion extensions other than the default and reside on read-only media.  In such
circumstances, stray cat files will be accepted with any compression extension
that is also supported for manual pages.

This special treatment of stray cat pages is removed if support for compressed
manual pages is turned off or not available.









































                                      [1m15[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m5.  Formatting[0m

As already pointed out in the introduction, there are two  primary  formatters
common to [1mUNIX[22m: [1mNROFF [22mand [1mTROFF[22m.

In  the following sections, I will use the term [1mTROFF [22mto describe the typeset-
ter formatter and [1mNROFF [22mto describe the typewriter formatter.  The  term  ROFF
will be used to describe a generic formatter.

[1m5.1.  GROFF[0m

If  using  the [1mGROFF [22mpackage, there is a further choice, [1mGROFF [22mitself.  Essen-
tially, [1mGROFF [22mforms a pipeline of processors including  [1mTROFF  [22mand  an  output
processor  which translates the ditroff produced by [1mTROFF [22minto the appropriate
output format.  The default output format, or device, for [1mGROFF [22mis PostScript.
Anything  else  must  be  specified  using the device argument.  To illustrate
[1mGROFF[22m, the command
     _______________________
     |_g_r_o_f_f__-_T_d_v_i__/_d_e_v_/_n_u_l_l_|_

will form the following pipeline

     troff -Tdvi /dev/null | grodvi

If [1mGROFF [22mis tied to [1mman[22m's [1m-T [22moption, it is still possible for [1mman  [22mto  produce
ditroff via use of the [1m-Z [22moption.

In  [1mGROFF  [22m1.09, [1mNROFF [22mis bundled as a shell script that calls [1mGROFF[22m, which in
turn calls [1mTROFF [22mwith the default options [1m-Wall  -mtty-char  -Tascii[22m,  passing
the result through [1mgrotty [22mbefore it finally reaches the screen.

It  is  imperative  that  the  script  does not pass pre-processing options to
[1mGROFF[22m's command line as [1mman [22mtakes care of this separately.

[1m5.2.  Devices[0m

Both [1mNROFF [22mand [1mGROFF [22mmay allow output device selection.  As  mentioned  previ-
ously, classic [1mNROFF [22mproduces output suitable for a typewriter device, classic
[1mTROFF [22mproduces output suitable for a [1mC/A/T [22mand [1mGROFF [22mproduces output  suitable
for a PostScript interpreting device by default.

[1m5.3.  Macros[0m

There  are  several  ROFF macro sets in existence that are suitable for manual
pages.  Unfortunately, they tend to be incompatible with each other.

During configuration, [1mconfigure [22mwill attempt to determine a suitable macro set
for  the local system's manual page collection.  It attempts to use [1mNROFF [22mwith
the following three macro packages:






                                      [1m16[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


          +--------------+--------------------------+---------------+
          |macro package | macro filename           | nroff command |
          +--------------+--------------------------+---------------+
          |andoc         | tmac.andoc or andoc.tmac | nroff -mandoc |
          |an            | tmac.an or an.tmac       | nroff -man    |
          |doc           | tmac.doc or doc.tmac     | nroff -mdoc   |
          +--------------+--------------------------+---------------+

The first that succeeds is used.  The [1mandoc [22mmacro set is suitable  for  manual
pages  written using either [1man [22mor [1mdoc [22mmacro commands, but not a combination of
both.

[1m5.4.  Pre-format processors (pre-processors)[0m

Manual pages may require pre-processing by any of the following


                      +--------+----+------------------+
                      |Program | ID | Pre-processes    |
                      +--------+----+------------------+
                      |eqn     | e  | equations        |
                      |tbl     | t  | tables           |
                      |grap    | g  | graphs           |
                      |pic     | p  | pictures         |
                      |refer   | r  | A bibliography   |
                      |vgrind  | v  | program listings |
                      +--------+----+------------------+

It is possible to assign a default pre-processor list that  all  manual  pages
will  be  passed  through prior to the primary formatter.  By default, this is
empty.  To define a default list, edit [4minclude/manconfig.h[24m and un-comment  the
following line

/* #define DEFAULT_MANROFFSEQ   "t" */

which  will enable [1mtbl [22mprocessing by default.  To change the list, replace the
[1mt [22mwith a suitable string of processor ID's.

Pre-process options may be provided at run time in various forms, but in  gen-
eral the pre-processors required by each manual page is indicated in the first
line of the manual page itself.  See [1mman[22m(1) for details.

If a manual page does not contain a pre-processor string in its first line, it
will  be  scanned  for  well-known ROFF requests used to pass input to certain
pre-processors.  Thus, the pre-processor string is often unnecessary for  cor-
rect output, but should nevertheless be included for efficiency.

[1m5.5.  Format scripts[0m

It is very likely that alternate systems manual pages may require non-standard
macro packages or possibly even special pre-processors.  To tackle such  prob-
lems, special format scripts may be created on a per manual hierarchy basis.



                                      [1m17[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


If the file

     [4m<manual_hierarchy>/mandb_nfmt[0m

exists and is executable, it is expected to be able to correctly format a man-
ual page originating from [4m<manual_hierarchy>[24m to its standard output.  It  will
be supplied with either two or three arguments:

    +o manual page filename
    +o pre-processor string
    +o output device (optional)

Similarly, if the option [1m-T[4m[22m<device>[24m or [1m-t [22mwas supplied to [1mman [22mand the file

     [4m<manual_hierarchy>/mandb_tfmt[0m

exists and is executable, it will be used in the same way.

An   example   of   such   a  script,  supplied  by  Markus  Armbruster  <arm-
bru@pond.sub.org>, who provided support for external formatter scripts, can be
found as [4mtools/mandb_fmt-script[0m

The  script can be used as both an [1mNROFF [22mand [1mTROFF[22m/[1mGROFF [22mformat script and can
be installed as [4mmandb_nfmt[24m and hard linked to  [4mmandb_tfmt[24m  after  modification
appropriate for your particular site.






























                                      [1m18[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m6.  The index database caches[0m

As  mentioned  in the introduction, man-db uses database lookups to search for
manual page locations and information.  When performing a manual  page  lookup
or a basic [1mwhatis [22msearch, the databases are searched in

     [4mkey[24m [4m->[24m [4mcontent[0m

mode  and  are  as  fast  as the underlying databases can be.  When performing
[1mapropos [22mor special [1mwhatis [22msearches, the databases are  searched  in  a  linear
way,  which,  although  far more expensive than [4mkeyed[24m lookup, is no worse than
traditional text based file searching.

[1m6.1.  index database location[0m

The databases are always located at  the  root  of  the  cat  page  hierarchy,
whether this is the same as the manual page hierarchy or not.  As file locking
mechanisms are employed to ensure that concurrent processes do  not  update  a
database  simultaneously, it is almost imperative that the databases reside on
a local filesystem since file locking across NFS filesystems may  be  unavail-
able  or  flaky.  To avoid such problems, [1mman [22mcan be compiled without database
maintenance support.  See the section titled "Modes of operation" for details.

[1m6.1.1.  Manual hierarchies with no index database[0m

It is possible for the man-db utilities to operate without aid from  an  index
database.   Under  such circumstances, search methods will use only file glob-
bing and whatis type searches are performed on  any  traditional  whatis  text
databases  that may exist.  Only the traditional cat hierarchy is searched for
cat files.

[1m6.1.2.  User manual page hierarchies[0m

A user may have any number of personal manual page hierarchies listed in their
$[1mMANPATH[22m.   By  default, [1mman [22mwill maintain [1mmandb [22mcreated databases at the root
of user manual page hierarchies.  The definition of a user manual hierarchy is
that  it  does  not  have an entry in the man-db configuration file.  See [1mman-[0m
[1mpath[22m(5) for details.

[1m6.2.  Contents of an index database[0m

There are four kinds of entry in an index database.

 (1)   A direct entry regarding a particular manual page.  Manual  pages  that
       are unique in terms of name use just a single entry in the database and
       can be looked up by simply using the name as the key.

 (2)   A common name index entry that lists the extensions of all of the  man-
       ual pages sharing the common index entry name.  Manual pages that share
       common names but have differing extensions each have a single  database
       entry,  but  this time they are looked up with a key comprised of their
       name and their extension.  The entire set of common  named  pages  also
       has  an  common  name  index  entry  that  informs  of  the  extensions


                                      [1m19[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


       available.

 (3)   An indirect entry that has a pointer to the real entry.   Manual  pages
       that are whatis references to a particular page do not physically exist
       so they have a pointer to the entry containing the location of the real
       manual page.

 (4)   Special  identification entries.  There is one special key name, "$ver-
       sion$" that identifies the database storage scheme version.

In order to support looking up manual pages  in  a  case-insensitive  fashion,
keys  are  stored  in  lower case.  If the name of the page was not already in
lower case, its true case is also stored in the common name index entry.

In the following entries, the character "|"  will  be  used  to  separate  the
fields. In reality a tab is used.  Direct and indirect entries takes the form:

     [4m<name>[24m   [4m->[24m   [4m<realname>|<ext>|<sec>|<mtime.sec>|<mtime.nsec>|<ID>|<ref>|[0m
     [4m<filter>|<comp>|<whatis>[0m

Common name index entries take the form:

     [4m<name>[24m [4m->[24m [4m|<realname1>|<ext1>|<realname2>|<ext2>|<realname3>|<ext3>|[24m  [4m...[0m
     [4m<realnamen>|<extn>[0m

and common name direct or indirect entries take the form:

     [4m<name>|<ext>[24m   [4m->[24m   [4m<realname>|<ext>|<sec>|<mtime.sec>|<mtime.nsec>|<ID>|[0m
     [4m<ref>|<filter>|<comp>|<whatis>[0m

where in each case the filename being represented is formed as

     [4m<manual_hierarchy>/man<sec>/<name>.<ext>.<comp>[0m

in the case of a manual page, or

     [4m<cat_hierarchy>/cat<sec>/<name>.<ext>.<comp>[0m

in the case of a stray cat.

If any of the fields would be empty, a single "-"  is  stored  in  its  place.
[4m<comp>[24m  represents the compression extension, [4m<mtime.sec>[24m is an integer repre-
senting the seconds part of the last modification time  of  the  manual  page,
[4m<mtime.nsec>[24m is an integer representing the nanoseconds part of the last modi-
fication time of the manual page, [4m<ref>[24m points to the entry containing the lo-
cation  of the real page, [4m<ID>[24m is one of the following identification letters,
and [4m<filter>[24m represents any preprocessors that are needed to display the page.








                                      [1m20[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


  +---+------------+--------------------------------------------------------+
  |ID | #define    | Description                                            |
  +---+------------+--------------------------------------------------------+
  |A  | ULT_MAN    | ultimate manual page, the full source nroff file       |
  |B  | SO_MAN     | manual page containing a .so request to an ULT_MAN     |
  |C  | WHATIS_MAN | virtual whatis referenced page pointing to an ULT_MAN  |
  |D  | STRAY_CAT  | cat page with no source manual page                    |
  |E  | WHATIS_CAT | virtual whatis referenced page pointing to a STRAY_CAT |
  +---+------------+--------------------------------------------------------+

The [4mID[24m illustrates the precedence.  Some types of manual page  can  be  refer-
enced  by  several  means,  e.g. .so requested and whatis referred.  In such a
case, only one reference must be stored in the database, the precedence  level
decides which.

[1m6.2.1.  Favouring stray cats[0m

With  the above rules of precedence, it is possible for a valid stray cat page
to be replaced by a whatis referred page sharing identical name-space.

If you  would  like  to  see  the  stray  cat  page  [1mkill[22m(1)  instead  of  the
[1mbash_builtins[22m(1)  page referenced by [1mkill[22m(1), edit [4minclude/manconfig.h[24m and un-
comment the following line

/* #define FAVOUR_STRAYCATS */

[1m6.2.2.  Accessdb[0m

A simple program, [1maccessdb [22mis included with man-db.  It will output  the  data
contained  within  a man-db database in a human readable form.  By default, it
will [4mdump[24m the data from [4m/var/cache/man/index.<db-type>[24m, where [4m<db-type>[24m is de-
pendent on the database library in use.

Supplying  an  argument  to [1maccessdb [22mwill override this default.  Tabs are re-
placed in the output by a tilde "~" in the [4mkey[24m field and a single space in the
[4mcontent[24m field.

[1m6.2.3.  Example database[0m

As an example of both [1maccessdb [22mand the database storage method, the output of
     ___________________________
     |_s_r_c_/_a_c_c_e_s_s_d_b__m_a_n_/_i_n_d_e_x_._b_t_|_

after first running
     _______________
     |_s_r_c_/_m_a_n_d_b__m_a_n_|_

from the top level build directory is included below.

$version$ -> "2.5.0"
accessdb -> "- 8 8 1410381979 324541691 A - - - dumps the content of a man-db database in a human readable format"
apropos -> "- 1 1 1410381979 268541692 A - - - search the manual page names and descriptions"



                                      [1m21[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


catman -> "- 8 8 1410381979 328541691 A - - - create or update the pre-formatted manual pages"
lexgrog -> "- 1 1 1410381979 268541692 A - - - parse header information in man pages"
man -> "- 1 1 1410381979 280541692 A - t - an interface to the on-line reference manuals"
manconv -> "- 1 1 1410381979 272541692 A - - - convert manual page from one encoding to another"
mandb -> "- 8 8 1410381979 324541691 A - t - create or update the manual page index caches"
manpath -> " manpath 5 manpath 1"
manpath~1 -> "- 1 1 1410381979 300541691 A - - - determine search path for manual pages"
manpath~5 -> "- 5 5 1410381979 304541691 A - - - format of the /etc/manpath.config file"
whatis -> "- 1 1 1410381979 300541691 A - - - display one-line manual page descriptions"
zsoelim -> "- 1 1 1410381979 304541691 A - - - satisfy .so requests in roff input"

[1m6.3.  Database types[0m

man-db  has  support  for various low level database libraries commonly in use
today.  The interfaces to the libraries are known as

 +o ndbm ([1mUNIX[22m)
 +o gdbm ([1mGNU[22m)
 +o btree (Berkeley DB)

man-db currently does not hold more than one database open at any time, so

 +o dbm ([1mUNIX[22m)

support could be added in the future.

[1m6.4.  Limitations[0m

The general differences and limitations are best compared in a table.


+------+-------------+----------+-----------------+--------------+-----------+
|      |             |   File   | Content memory  |  Concurrent  |           |
|Name  |    Type     |          +---------+-------+              | Shareable |
|      |             |   name   |  type   | limit |    access    |           |
+------+-------------+----------+---------+-------+--------------+-----------+
|ndbm  | hash        | index10  | static  | 1Kb   | none         | no        |
|gdbm  | hash        | index.db | dynamic | -     | file locking | no        |
|btree | binary tree | index.bt | static  | -     | none         | yes       |
+------+-------------+----------+---------+-------+--------------+-----------+

Those types that have no built in concurrent access strategy are provided with
[1mflock[22m(2) based file locking by man-db.

Berkeley DB initializes its databases very quickly, so  [1mbtree  [22mmay  have  some
performance  advantages  when doing [1mman [22msearches.  However, it is quite heavy-
weight and its library SONAME and on-disk formats have  changed  a  number  of
times  to  provide  features  considerably  beyond  what  man-db needs, so the
____________________
   10 ndbm databases are physically represented by two  files,  [4mindex.dir[24m  and
[4mindex.pag[24m, but are referred to simply as [4mindex[24m by the interface routines.




                                      [1m22[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


preferred library interface is now [1mgdbm[22m.  [1mconfigure [22mwill look for [1mgdbm[22m,  [1mbtree[0m
and then finally [1mndbm [22mroutines when configuring man-db.

[1m6.5.  Sharing databases in a heterogeneous environment[0m
It  may  be necessary or advantageous to share databases across platforms, re-
gardless of the potential file locking problems.

An example would be a user having a personal manual page hierarchy in  an  NFS
based  home  directory  environment, whereby the home directory is held on and
mounted from a single machine in a heterogeneous network.

In this context, the database cache will have the same name and reside in  the
same  place  on  all  machines.  There are at least two ways to deal with this
problem.

 +o Hack the [4minclude/manconfig.h[24m file on each  platform  to  provide  a  unique
   database name for each system.  No databases will be shared.
 +o Install  and  use  the Berkeley DB database interface library on each plat-
   form.  These databases can be shared across big-endian/little-endian  plat-
   forms  although  a  database created on a big-endian platform will suffer a
   small access penalty when used by a litle-endian machine and vice-versa.


































                                      [1m23[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m7.  Miscellaneous[0m

[1m7.1.  Modes of operation[0m

The man-db utilities can operate in many different modes, allowing varying de-
grees  of freedom, functionality and security.  No mode requires that the man-
ual page hierarchies be writable.

(1) Default mode
     [1mman [22mis setuid to the user MAN_OWNER which is  `man'  by  default  and  is
     changeable  via  options to [1mconfigure[22m.  [1mmandb[22m, if run by the superuser or
     MAN_OWNER,  creates  globally  accessible  index   databases   owned   by
     MAN_OWNER.   Once  the  databases are created, [1mman [22mwill update entries in
     them if it finds newly installed manual pages (if the  [1m--update  [22mflag  is
     used)  or delete entries if manual pages are removed.  In this mode it is
     possible for a malicious [1mman [22muser to deliberately lock a  database  as  a
     writer, thus denying read access to other users.
     If  cat directories exist and have the correct permissions, [1mman [22mwill take
     care of producing cat files.  These will be owned by MAN_OWNER.  The  de-
     fault permissions of both cat files and databases are 0644.

(2) No man database updates
     This mode also requires [1mman [22mto be setuid, but is favoured where databases
     must be shared in an environment unfriendly to kernel locking procedures,
     eg.  NFS.  It also prevents possible "denial of service" attacks by mali-
     cious [1mman [22musers as [1mman [22mnever opens the databases  as  a  writer  in  this
     mode.   To replace the functionality lost by disallowing [1mman [22mwrite access
     to the databases, [1mmandb [22mshould be rerun whenever new manual pages are in-
     stalled.  Otherwise, [1mman [22mwill not be able to use the database to find and
     display the newly added manual pages, and will have to use the filesystem
     instead.   Each index database may be owned by an arbitrary user who will
     have subsequent write access to the database.  Cat files are  created  in
     the same way as for mode (1) above.
     To  use the man-db utilities in this mode, give the option `--disable-au-
     tomatic-update' to [1mconfigure[22m.

(3) No man database updates or cat production
     [1mman [22mis installed not setuid.  This mode of operation probably offers  the
     highest  level  of  security but it requires higher levels of maintenance
     than other modes due to the restrictions imposed upon [1mman[22m.  Each database
     is owned by an arbitrary user as in mode (2).  Each cat hierarchy is also
     owned by an arbitrary user who is responsible for creating cat files  us-
     ing  [1mcatman  [22mwhenever  new  manual files are installed.  [1mman [22mwill be com-
     pletely passive in its action, i.e. no index databases will be written to
     and no cat files are ever produced.
     To  use  the  man-db  utilities  in this mode, supply the options `--dis-
     able-cache-owner   --disable-setuid   --disable-automatic-update   --dis-
     able-cats'  to  [1mconfigure[22m, or build man-db as in mode (1) and install the
     binaries without the setuid bit set.

(4) Wide open
     [1mman [22mis installed not setuid.  This mode is similar in  operation  to  the
     majority of vendor supplied, non setuid, cat file supporting manual pager


                                      [1m24[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


     suites.  It is not recommended.  The databases are owned by an  arbitrary
     user  who maintains them using [1mmandb[22m.  [1mman [22mdoes not update the databases.
     Cat files are produced and stored in world writable cat  directories  and
     have world write access themselves.
     To  use  the  man-db  utilities  in this mode, supply the options `--dis-
     able-cache-owner --disable-setuid --disable-automatic-update' to  [1mconfig-[0m
     [1mure[22m,  edit  [4minclude/manconfig.h[24m and change the definition of CATMODE from
     0644 to 0666.

Other variations can also be used.  In fact it is possible for [1mman [22mto actually
create  index  databases,  usually the job of [1mmandb[22m, for users' private manual
page hierarchies.  This  is  enabled  by  giving  the  option  `--enable-auto-
matic-create' to [1mconfigure[22m.

In summary, [4minclude/manconfig.h[24m contains definitions for

 +o CATMODE
 +o DBMODE

the  setuid  installation and operation of [1mman [22mis modified by supplying either
of the following options to [1mconfigure[22m:

 +o --enable-setuid
 +o --disable-setuid

and other aspects of [1mman[22m's behaviour are controlled by the  following  options
to [1mconfigure[22m:

 +o --enable-automatic-create
 +o --disable-automatic-update
 +o --disable-cats

[1m7.2.  NFS root squash[0m

If [1mman [22mis installed setuid to an arbitrary user and is run by root, instead of
gaining the effective user id of the setuid user, [1mman [22mis run with both uid and
euid  as  root.  This is neccesary due to infelicities with the [1mPOSIX [22msetuid()
function call:  All users except root may change to  and  from  the  effective
(setuid) user, however once root has setuid(user), there is no way back.

A side effect of this is that [1mNFS [22mmounted cat hierarchies or databases will be
unwritable if the following conditions exist:

 +o man/catman/mandb is run by root
 +o The NFS mount has the root squash flag set

To get around this problem, the root user must first attain the ID of the  cat
hierarchy or database owner before running [1mman/catman/mandb [22mwhenever the data-
bases need updating or cat files are to be produced.






                                      [1m25[0m







[1mman-db                              v2.8.7                      April 19, 2021[0m


[1m7.3.  NLS message catalogues[0m

man-db has built in support for native language message catalogues.  That  is,
it  can issue messages in the locale of the user's choice.  This will only oc-
cur if the locale's translation has been written.  Before undertaking a trans-
lation,   please  contact  the  Translation  Project  (https://translationpro-
ject.org/) who are coordinating such activities.

[1m7.4.  Credits[0m

The authors would like to thank the following people for their  time,  effort,
support, ideas and code which went into man-db:

    Markus Armbruster <armbru@pond.sub.org>
    Lionel Cons & colleages <cons@dxcern.cern.ch>
    Carl Edman <cedman@princeton.edu>
    Caleb Epstein <epstein_caleb@jpmorgan.com>
    Lars Fenneberg <lf@gimli.comlink.de>
    Zoltan Hidvegi <hzoli@cs.elte.hu>
    Nils Magnus <magnus@unix-ag.uni-kl.de>
    Daniel Quinlan <quinlan@yggdrasil.com>
    Fabrizio Polacco <fpolacco@debian.org>
    Gordon Sadler <gbsadler1@lcisp.com>
    Colin Phipps <cph@cph.demon.co.uk>
    Paul Slootman <paul@wurtel.net>
    Jose Rodriguez <boriel@airtel.net>
    Eirik Fuller <eirik@hackrat.com>
    Matej Vela <vela@debian.org>
    Clint Adams <schizo@debian.org>
    Jeremy C. Reed <reed@reedmedia.net>
    Erik Andersen <andersen@codepoet.org>
    Giuseppe Sacco <eppesuig@debian.org>
    David Weinehall <tao@debian.org>
    Ralph Corderoy <ralph@inputplus.co.uk>
    Yuri Kozlov <kozlov.y@gmail.com>
    Henning Makholm <henning@makholm.net>
    Lars Wirzenius <liw@iki.fi>
    Nicolas Fran,cois <nicolas.francois@centraliens.net>
    Ivan Shmakov <oneingray@gmail.com>
    Peter Breitenlohner <peb@mppmu.mpg.de>
    Robert Luberda <robert@debian.org>
    Chusslove Illich <caslav.ilic@gmx.net>

and all those translators listed in the [1mman/THANKS [22mfile.











                                      [1m26[0m










                                   Glossary


manual page
     A  file  containing descriptions related to the use of a function or pro-
     gram or the structure of a file.  The name of the file is formed from the
     title of the manual page followed by a period followed by the name of the
     section that it resides in, optionally followed  by  an  extension.   The
     format of the file is [1mNROFF [22mand may be compressed, having a suitable com-
     pression extension appended.

cat page
     A formatted manual page suitable for viewing on a vt100-type terminal.

stray cat page
     A cat page that does not have a relative manual page on the system,  i.e.
     only  the  cat page was supplied or the manual page was removed after the
     cat page had been created.

section
     Each manual page or cat page hierarchy is  divided  into  sections,  each
     section  having  its  own directory.  Manual page hierarchy section names
     begin with `man' and cat page sections with `cat'.

extension
     A package may provide manual pages with filenames ending  in  a  package-
     specific extension name.  This allows manual pages with the same title to
     coexist in the same manual page hierarchy and section without sharing the
     same  filename.   It  also provides a further mechanism for man to select
     the correct manual page.

manual page hierarchy
     A directory tree divided into manual page  sections,  each  containing  a
     collection of manual pages.

cat page hierarchy
     A  directory  tree divided into cat page sections, each containing a col-
     lection of cat pages.

traditional cat page hierarchy
     The same location as the manual page hierarchy.

alternate cat page hierarchy
     A separate location to that of the traditional cat page hierarchy.

traditional cat page
     A cat page located in a traditional cat page hierarchy.

alternate cat page
     A cat page located in an alternate cat page hierarchy.





                                       [1mi[0m










                                     Contents


1.  Introduction ........................................................    1
    1.1  man-db .........................................................    1
         1.1.1  The concept .............................................    1
    1.2  The manual page system .........................................    2
    1.3  Sections of the manual .........................................    2
    1.4  The format of manual pages .....................................    3
    1.5  Arguments to configure .........................................    3

2.  The specifics of Sections ...........................................    5
    2.1  Package specific manual page sections ..........................    5
    2.2  Selecting a section type .......................................    5
         2.2.1  Specifying a section ....................................    5
         2.2.2  Specifying an extension .................................    6

3.  Filesystem structure ................................................    7
    3.1  Manual page hierarchies ........................................    7
    3.2  Setting the MANPATH ............................................    7
    3.3  Determination of the internal manpath ..........................    8
    3.4  Other OS's manual pages ........................................    8
    3.5  NLS manual pages ...............................................    9
         3.5.1  ISO 8859-1 (latin1) manual pages ........................   11
         3.5.2  Displaying non-ASCII characters  on  a  Linux  virtual
         terminal .......................................................   11
         3.5.3  Viewing ASCII pages formatted for latin1 output device
         ................................................................   11
    3.6  Cat pages ......................................................   12
    3.7  Cat page hierarchies ...........................................   12
    3.8  Local cat page directory caches ................................   13

4.  Compression .........................................................   14
    4.1  Compressed manual pages ........................................   14
    4.2  Compressed cat pages ...........................................   14
         4.2.1  Stray cats ..............................................   15

5.  Formatting ..........................................................   16
    5.1  [1mGROFF [22m..........................................................   16
    5.2  Devices ........................................................   16
    5.3  Macros .........................................................   16
    5.4  Pre-format processors (pre-processors) .........................   17
    5.5  Format scripts .................................................   17

6.  The index database caches ...........................................   19
    6.1  index database location ........................................   19
         6.1.1  Manual hierarchies with no index database ...............   19
         6.1.2  User manual page hierarchies ............................   19
    6.2  Contents of an index database ..................................   19
         6.2.1  Favouring stray cats ....................................   21
         6.2.2  Accessdb ................................................   21
         6.2.3  Example database ........................................   21
    6.3  Database types .................................................   22


                                       [1mi[0m










    6.4  Limitations ....................................................   22
    6.5  Sharing databases in a heterogeneous environment ...............   23

7.  Miscellaneous .......................................................   24
    7.1  Modes of operation .............................................   24
    7.2  NFS root squash ................................................   25
    7.3  NLS message catalogues .........................................   26
    7.4  Credits ........................................................   26















































                                      [1mii[0m



