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Filename : man-db-manual.txt
back



















               [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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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[0m
respectively.  Thus, sections are used to  separate  out  the  program  manual
pages  from  the  function  manual pages and so on.  The table below shows the
____________________
   2 one line description of the manual page




                                       [1m2[0m







[1mman-db                             v2.7.6.1                    October 8, 2021[0m


[4msection[24m 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                             v2.7.6.1                    October 8, 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,
     especially  when  the  names  of  some manual pages on the system contain
     periods.  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.









                                       [1m4[0m







[1mman-db                             v2.7.6.1                    October 8, 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
allows 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                             v2.7.6.1                    October 8, 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,
including sections found in imported manual page hierarchies.  It is not  nec-
essary  to  list  sections with extensions unless a special ordering for those
extensions is desired.  The order is important because  in  normal  operation,
[1mman  [22mwill  only  display  the first manual page it finds that meets the search
criteria. 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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
appended 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
together  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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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
encoded 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                             v2.7.6.1                    October 8, 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
enable 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                             v2.7.6.1                    October 8, 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
devices 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
   accessed cat files.

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




                                      [1m12[0m







[1mman-db                             v2.7.6.1                    October 8, 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
default, the cat page hierarchy shadows the manual page  hierarchy.   The  [1mFHS[0m
proposes  [4m/var/cache/man[24m as the location for such directories, although man-db
allows 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
under  [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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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
location of the real page, [4m<ID>[24m is one of the  following  identification  let-
ters, and [4m<filter>[24m represents any preprocessors that are needed to display the
page.







                                      [1m20[0m







[1mman-db                             v2.7.6.1                    October 8, 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
dependent on the database library in use.

Supplying  an  argument  to  [1maccessdb  [22mwill  override  this default.  Tabs are
replaced 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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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,
regardless 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                             v2.7.6.1                    October 8, 2021[0m


[1m7.  Miscellaneous[0m

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

The man-db utilities can operate in many  different  modes,  allowing  varying
degrees  of  freedom,  functionality  and security.  No mode requires that the
manual 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
     default 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
     installed.   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 `--dis-
     able-automatic-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
     using  [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                             v2.7.6.1                    October 8, 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                             v2.7.6.1                    October 8, 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
occur if the locale's translation has  been  written.   Before  undertaking  a
translation,  please  contact  the Translation Project (http://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