src/Doc/System/Basics.thy
author wenzelm
Sat Nov 24 12:39:58 2012 +0100 (2012-11-24)
changeset 50182 30177ec0be36
parent 49173 fa01a202399c
child 50197 b385d134926d
permissions -rw-r--r--
added ISABELLE_PLATFORM_FAMILY;
     1 theory Basics
     2 imports Base
     3 begin
     4 
     5 chapter {* The Isabelle system environment *}
     6 
     7 text {* This manual describes Isabelle together with related tools and
     8   user interfaces as seen from a system oriented view.  See also the
     9   \emph{Isabelle/Isar Reference Manual}~\cite{isabelle-isar-ref} for
    10   the actual Isabelle input language and related concepts, and
    11   \emph{The Isabelle/Isar Implementation
    12   Manual}~\cite{isabelle-implementation} for the main concepts of the
    13   underlying implementation in Isabelle/ML.
    14 
    15   \medskip The Isabelle system environment provides the following
    16   basic infrastructure to integrate tools smoothly.
    17 
    18   \begin{enumerate}
    19 
    20   \item The \emph{Isabelle settings} mechanism provides process
    21   environment variables to all Isabelle executables (including tools
    22   and user interfaces).
    23 
    24   \item The raw \emph{Isabelle process} (@{executable_ref
    25   "isabelle-process"}) runs logic sessions either interactively or in
    26   batch mode.  In particular, this view abstracts over the invocation
    27   of the actual ML system to be used.  Regular users rarely need to
    28   care about the low-level process.
    29 
    30   \item The main \emph{Isabelle tool wrapper} (@{executable_ref
    31   isabelle}) provides a generic startup environment Isabelle related
    32   utilities, user interfaces etc.  Such tools automatically benefit
    33   from the settings mechanism.
    34 
    35   \end{enumerate}
    36 *}
    37 
    38 
    39 section {* Isabelle settings \label{sec:settings} *}
    40 
    41 text {*
    42   The Isabelle system heavily depends on the \emph{settings
    43   mechanism}\indexbold{settings}.  Essentially, this is a statically
    44   scoped collection of environment variables, such as @{setting
    45   ISABELLE_HOME}, @{setting ML_SYSTEM}, @{setting ML_HOME}.  These
    46   variables are \emph{not} intended to be set directly from the shell,
    47   though.  Isabelle employs a somewhat more sophisticated scheme of
    48   \emph{settings files} --- one for site-wide defaults, another for
    49   additional user-specific modifications.  With all configuration
    50   variables in clearly defined places, this scheme is more
    51   maintainable and user-friendly than global shell environment
    52   variables.
    53 
    54   In particular, we avoid the typical situation where prospective
    55   users of a software package are told to put several things into
    56   their shell startup scripts, before being able to actually run the
    57   program. Isabelle requires none such administrative chores of its
    58   end-users --- the executables can be invoked straight away.
    59   Occasionally, users would still want to put the @{file
    60   "$ISABELLE_HOME/bin"} directory into their shell's search path, but
    61   this is not required.
    62 *}
    63 
    64 
    65 subsection {* Bootstrapping the environment \label{sec:boot} *}
    66 
    67 text {* Isabelle executables need to be run within a proper settings
    68   environment.  This is bootstrapped as described below, on the first
    69   invocation of one of the outer wrapper scripts (such as
    70   @{executable_ref isabelle}).  This happens only once for each
    71   process tree, i.e.\ the environment is passed to subprocesses
    72   according to regular Unix conventions.
    73 
    74   \begin{enumerate}
    75 
    76   \item The special variable @{setting_def ISABELLE_HOME} is
    77   determined automatically from the location of the binary that has
    78   been run.
    79   
    80   You should not try to set @{setting ISABELLE_HOME} manually. Also
    81   note that the Isabelle executables either have to be run from their
    82   original location in the distribution directory, or via the
    83   executable objects created by the @{tool install} tool.  Symbolic
    84   links are admissible, but a plain copy of the @{file
    85   "$ISABELLE_HOME/bin"} files will not work!
    86 
    87   \item The file @{file "$ISABELLE_HOME/etc/settings"} is run as a
    88   @{executable_ref bash} shell script with the auto-export option for
    89   variables enabled.
    90   
    91   This file holds a rather long list of shell variable assigments,
    92   thus providing the site-wide default settings.  The Isabelle
    93   distribution already contains a global settings file with sensible
    94   defaults for most variables.  When installing the system, only a few
    95   of these may have to be adapted (probably @{setting ML_SYSTEM}
    96   etc.).
    97   
    98   \item The file @{verbatim "$ISABELLE_HOME_USER/etc/settings"} (if it
    99   exists) is run in the same way as the site default settings. Note
   100   that the variable @{setting ISABELLE_HOME_USER} has already been set
   101   before --- usually to something like @{verbatim
   102   "$USER_HOME/.isabelle/IsabelleXXXX"}.
   103   
   104   Thus individual users may override the site-wide defaults.  See also
   105   file @{file "$ISABELLE_HOME/etc/user-settings.sample"} in the
   106   distribution.  Typically, a user settings file would contain only a
   107   few lines, just the assigments that are really changed.  One should
   108   definitely \emph{not} start with a full copy the basic @{file
   109   "$ISABELLE_HOME/etc/settings"}. This could cause very annoying
   110   maintainance problems later, when the Isabelle installation is
   111   updated or changed otherwise.
   112   
   113   \end{enumerate}
   114 
   115   Since settings files are regular GNU @{executable_def bash} scripts,
   116   one may use complex shell commands, such as @{verbatim "if"} or
   117   @{verbatim "case"} statements to set variables depending on the
   118   system architecture or other environment variables.  Such advanced
   119   features should be added only with great care, though. In
   120   particular, external environment references should be kept at a
   121   minimum.
   122 
   123   \medskip A few variables are somewhat special:
   124 
   125   \begin{itemize}
   126 
   127   \item @{setting_def ISABELLE_PROCESS} and @{setting_def ISABELLE_TOOL} are set
   128   automatically to the absolute path names of the @{executable
   129   "isabelle-process"} and @{executable isabelle} executables,
   130   respectively.
   131   
   132   \item @{setting_ref ISABELLE_OUTPUT} will have the identifiers of
   133   the Isabelle distribution (cf.\ @{setting ISABELLE_IDENTIFIER}) and
   134   the ML system (cf.\ @{setting ML_IDENTIFIER}) appended automatically
   135   to its value.
   136 
   137   \end{itemize}
   138 
   139   \medskip Note that the settings environment may be inspected with
   140   the @{tool getenv} tool.  This might help to figure out the effect
   141   of complex settings scripts.  *}
   142 
   143 
   144 subsection {* Common variables *}
   145 
   146 text {*
   147   This is a reference of common Isabelle settings variables. Note that
   148   the list is somewhat open-ended. Third-party utilities or interfaces
   149   may add their own selection. Variables that are special in some
   150   sense are marked with @{text "\<^sup>*"}.
   151 
   152   \begin{description}
   153 
   154   \item[@{setting_def USER_HOME}@{text "\<^sup>*"}] Is the cross-platform
   155   user home directory.  On Unix systems this is usually the same as
   156   @{setting HOME}, but on Windows it is the regular home directory of
   157   the user, not the one of within the Cygwin root
   158   file-system.\footnote{Cygwin itself offers another choice whether
   159   its HOME should point to the \texttt{/home} directory tree or the
   160   Windows user home.}
   161 
   162  \item[@{setting_def ISABELLE_HOME}@{text "\<^sup>*"}] is the location of the
   163   top-level Isabelle distribution directory. This is automatically
   164   determined from the Isabelle executable that has been invoked.  Do
   165   not attempt to set @{setting ISABELLE_HOME} yourself from the shell!
   166   
   167   \item[@{setting_def ISABELLE_HOME_USER}] is the user-specific
   168   counterpart of @{setting ISABELLE_HOME}. The default value is
   169   relative to @{verbatim "$USER_HOME/.isabelle"}, under rare
   170   circumstances this may be changed in the global setting file.
   171   Typically, the @{setting ISABELLE_HOME_USER} directory mimics
   172   @{setting ISABELLE_HOME} to some extend. In particular, site-wide
   173   defaults may be overridden by a private @{verbatim
   174   "$ISABELLE_HOME_USER/etc/settings"}.
   175 
   176   \item[@{setting_def ISABELLE_PLATFORM_FAMILY}@{text "\<^sup>*"}] is
   177   automatically set to the general platform family: @{verbatim linux},
   178   @{verbatim macos}, @{verbatim windows}.  Note that
   179   platform-dependent tools usually need to refer to the more specific
   180   identification according to @{setting ISABELLE_PLATFORM}, @{setting
   181   ISABELLE_PLATFORM32}, @{setting ISABELLE_PLATFORM64}.
   182 
   183   \item[@{setting_def ISABELLE_PLATFORM}@{text "\<^sup>*"}] is automatically
   184   set to a symbolic identifier for the underlying hardware and
   185   operating system.  The Isabelle platform identification always
   186   refers to the 32 bit variant, even this is a 64 bit machine.  Note
   187   that the ML or Java runtime may have a different idea, depending on
   188   which binaries are actually run.
   189 
   190   \item[@{setting_def ISABELLE_PLATFORM64}@{text "\<^sup>*"}] is similar to
   191   @{setting ISABELLE_PLATFORM} but refers to the proper 64 bit variant
   192   on a platform that supports this; the value is empty for 32 bit.
   193   Note that the following bash expression (including the quotes)
   194   prefers the 64 bit platform, if that is available:
   195 
   196   @{verbatim [display] "\"${ISABELLE_PLATFORM64:-$ISABELLE_PLATFORM}\""}
   197 
   198   \item[@{setting_def ISABELLE_PROCESS}@{text "\<^sup>*"}, @{setting
   199   ISABELLE_TOOL}@{text "\<^sup>*"}] are automatically set to the full path
   200   names of the @{executable "isabelle-process"} and @{executable
   201   isabelle} executables, respectively.  Thus other tools and scripts
   202   need not assume that the @{file "$ISABELLE_HOME/bin"} directory is
   203   on the current search path of the shell.
   204   
   205   \item[@{setting_def ISABELLE_IDENTIFIER}@{text "\<^sup>*"}] refers
   206   to the name of this Isabelle distribution, e.g.\ ``@{verbatim
   207   Isabelle2012}''.
   208 
   209   \item[@{setting_def ML_SYSTEM}, @{setting_def ML_HOME},
   210   @{setting_def ML_OPTIONS}, @{setting_def ML_PLATFORM}, @{setting_def
   211   ML_IDENTIFIER}@{text "\<^sup>*"}] specify the underlying ML system
   212   to be used for Isabelle.  There is only a fixed set of admissable
   213   @{setting ML_SYSTEM} names (see the @{file
   214   "$ISABELLE_HOME/etc/settings"} file of the distribution).
   215   
   216   The actual compiler binary will be run from the directory @{setting
   217   ML_HOME}, with @{setting ML_OPTIONS} as first arguments on the
   218   command line.  The optional @{setting ML_PLATFORM} may specify the
   219   binary format of ML heap images, which is useful for cross-platform
   220   installations.  The value of @{setting ML_IDENTIFIER} is
   221   automatically obtained by composing the values of @{setting
   222   ML_SYSTEM}, @{setting ML_PLATFORM} and the Isabelle version values.
   223 
   224   \item[@{setting_def ISABELLE_JDK_HOME}] needs to point to a full JDK
   225   (Java Development Kit) installation with @{verbatim javac} and
   226   @{verbatim jar} executables.  This is essential for Isabelle/Scala
   227   and other JVM-based tools to work properly.  Note that conventional
   228   @{verbatim JAVA_HOME} usually points to the JRE (Java Runtime
   229   Environment), not JDK.
   230   
   231   \item[@{setting_def ISABELLE_PATH}] is a list of directories
   232   (separated by colons) where Isabelle logic images may reside.  When
   233   looking up heaps files, the value of @{setting ML_IDENTIFIER} is
   234   appended to each component internally.
   235   
   236   \item[@{setting_def ISABELLE_OUTPUT}@{text "\<^sup>*"}] is a
   237   directory where output heap files should be stored by default. The
   238   ML system and Isabelle version identifier is appended here, too.
   239   
   240   \item[@{setting_def ISABELLE_BROWSER_INFO}] is the directory where
   241   theory browser information (HTML text, graph data, and printable
   242   documents) is stored (see also \secref{sec:info}).  The default
   243   value is @{verbatim "$ISABELLE_HOME_USER/browser_info"}.
   244   
   245   \item[@{setting_def ISABELLE_LOGIC}] specifies the default logic to
   246   load if none is given explicitely by the user.  The default value is
   247   @{verbatim HOL}.
   248   
   249   \item[@{setting_def ISABELLE_LINE_EDITOR}] specifies the default
   250   line editor for the @{tool_ref tty} interface.
   251 
   252   \item[@{setting_def ISABELLE_USEDIR_OPTIONS}] is implicitly prefixed
   253   to the command line of any @{tool_ref usedir} invocation. This
   254   typically contains compilation options for object-logics --- @{tool
   255   usedir} is the basic tool for managing logic sessions (cf.\ the
   256   @{verbatim IsaMakefile}s in the distribution).
   257 
   258   \item[@{setting_def ISABELLE_LATEX}, @{setting_def
   259   ISABELLE_PDFLATEX}, @{setting_def ISABELLE_BIBTEX}, @{setting_def
   260   ISABELLE_DVIPS}] refer to {\LaTeX} related tools for Isabelle
   261   document preparation (see also \secref{sec:tool-latex}).
   262   
   263   \item[@{setting_def ISABELLE_TOOLS}] is a colon separated list of
   264   directories that are scanned by @{executable isabelle} for external
   265   utility programs (see also \secref{sec:isabelle-tool}).
   266   
   267   \item[@{setting_def ISABELLE_DOCS}] is a colon separated list of
   268   directories with documentation files.
   269   
   270   \item[@{setting_def ISABELLE_DOC_FORMAT}] specifies the preferred
   271   document format, typically @{verbatim dvi} or @{verbatim pdf}.
   272   
   273   \item[@{setting_def DVI_VIEWER}] specifies the command to be used
   274   for displaying @{verbatim dvi} files.
   275   
   276   \item[@{setting_def PDF_VIEWER}] specifies the command to be used
   277   for displaying @{verbatim pdf} files.
   278   
   279   \item[@{setting_def PRINT_COMMAND}] specifies the standard printer
   280   spool command, which is expected to accept @{verbatim ps} files.
   281   
   282   \item[@{setting_def ISABELLE_TMP_PREFIX}@{text "\<^sup>*"}] is the
   283   prefix from which any running @{executable "isabelle-process"}
   284   derives an individual directory for temporary files.  The default is
   285   somewhere in @{verbatim "/tmp"}.
   286   
   287   \end{description}
   288 *}
   289 
   290 
   291 subsection {* Additional components \label{sec:components} *}
   292 
   293 text {* Any directory may be registered as an explicit \emph{Isabelle
   294   component}.  The general layout conventions are that of the main
   295   Isabelle distribution itself, and the following two files (both
   296   optional) have a special meaning:
   297 
   298   \begin{itemize}
   299 
   300   \item @{verbatim "etc/settings"} holds additional settings that are
   301   initialized when bootstrapping the overall Isabelle environment,
   302   cf.\ \secref{sec:boot}.  As usual, the content is interpreted as a
   303   @{verbatim bash} script.  It may refer to the component's enclosing
   304   directory via the @{verbatim "COMPONENT"} shell variable.
   305 
   306   For example, the following setting allows to refer to files within
   307   the component later on, without having to hardwire absolute paths:
   308 
   309 \begin{ttbox}
   310 MY_COMPONENT_HOME="$COMPONENT"
   311 \end{ttbox}
   312 
   313   Components can also add to existing Isabelle settings such as
   314   @{setting_def ISABELLE_TOOLS}, in order to provide
   315   component-specific tools that can be invoked by end-users.  For
   316   example:
   317 
   318 \begin{ttbox}
   319 ISABELLE_TOOLS="$ISABELLE_TOOLS:$COMPONENT/lib/Tools"
   320 \end{ttbox}
   321 
   322   \item @{verbatim "etc/components"} holds a list of further
   323   sub-components of the same structure.  The directory specifications
   324   given here can be either absolute (with leading @{verbatim "/"}) or
   325   relative to the component's main directory.
   326 
   327   \end{itemize}
   328 
   329   The root of component initialization is @{setting ISABELLE_HOME}
   330   itself.  After initializing all of its sub-components recursively,
   331   @{setting ISABELLE_HOME_USER} is included in the same manner (if
   332   that directory exists).  This allows to install private components
   333   via @{verbatim "$ISABELLE_HOME_USER/etc/components"}, although it is
   334   often more convenient to do that programmatically via the
   335   \verb,init_component, shell function in the \verb,etc/settings,
   336   script of \verb,$ISABELLE_HOME_USER, (or any other component
   337   directory).  For example:
   338 \begin{ttbox}
   339 init_component "$HOME/screwdriver-2.0"
   340 \end{ttbox}
   341 
   342   This is tolerant wrt.\ missing component directories, but might
   343   produce a warning.
   344 
   345   \medskip More complex situations may be addressed by initializing
   346   components listed in a given catalog file, relatively to some base
   347   directory:
   348 
   349 \begin{ttbox}
   350 init_components "$HOME/my_component_store" "some_catalog_file"
   351 \end{ttbox}
   352 
   353   The component directories listed in the catalog file are treated as
   354   relative to the given base directory.
   355 
   356   See also \secref{sec:tool-components} for some tool-support for
   357   resolving components that are formally initialized but not installed
   358   yet.
   359 *}
   360 
   361 
   362 section {* The raw Isabelle process *}
   363 
   364 text {*
   365   The @{executable_def "isabelle-process"} executable runs bare-bones
   366   Isabelle logic sessions --- either interactively or in batch mode.
   367   It provides an abstraction over the underlying ML system, and over
   368   the actual heap file locations.  Its usage is:
   369 
   370 \begin{ttbox}
   371 Usage: isabelle-process [OPTIONS] [INPUT] [OUTPUT]
   372 
   373   Options are:
   374     -I           startup Isar interaction mode
   375     -P           startup Proof General interaction mode
   376     -S           secure mode -- disallow critical operations
   377     -T ADDR      startup process wrapper, with socket address
   378     -W IN:OUT    startup process wrapper, with input/output fifos
   379     -X           startup PGIP interaction mode
   380     -e MLTEXT    pass MLTEXT to the ML session
   381     -f           pass 'Session.finish();' to the ML session
   382     -m MODE      add print mode for output
   383     -q           non-interactive session
   384     -r           open heap file read-only
   385     -u           pass 'use"ROOT.ML";' to the ML session
   386     -w           reset write permissions on OUTPUT
   387 
   388   INPUT (default "\$ISABELLE_LOGIC") and OUTPUT specify in/out heaps.
   389   These are either names to be searched in the Isabelle path, or
   390   actual file names (containing at least one /).
   391   If INPUT is "RAW_ML_SYSTEM", just start the bare bones ML system.
   392 \end{ttbox}
   393 
   394   Input files without path specifications are looked up in the
   395   @{setting ISABELLE_PATH} setting, which may consist of multiple
   396   components separated by colons --- these are tried in the given
   397   order with the value of @{setting ML_IDENTIFIER} appended
   398   internally.  In a similar way, base names are relative to the
   399   directory specified by @{setting ISABELLE_OUTPUT}.  In any case,
   400   actual file locations may also be given by including at least one
   401   slash (@{verbatim "/"}) in the name (hint: use @{verbatim "./"} to
   402   refer to the current directory).
   403 *}
   404 
   405 
   406 subsubsection {* Options *}
   407 
   408 text {*
   409   If the input heap file does not have write permission bits set, or
   410   the @{verbatim "-r"} option is given explicitely, then the session
   411   started will be read-only.  That is, the ML world cannot be
   412   committed back into the image file.  Otherwise, a writable session
   413   enables commits into either the input file, or into another output
   414   heap file (if that is given as the second argument on the command
   415   line).
   416 
   417   The read-write state of sessions is determined at startup only, it
   418   cannot be changed intermediately. Also note that heap images may
   419   require considerable amounts of disk space (approximately
   420   50--200~MB). Users are responsible for themselves to dispose their
   421   heap files when they are no longer needed.
   422 
   423   \medskip The @{verbatim "-w"} option makes the output heap file
   424   read-only after terminating.  Thus subsequent invocations cause the
   425   logic image to be read-only automatically.
   426 
   427   \medskip Using the @{verbatim "-e"} option, arbitrary ML code may be
   428   passed to the Isabelle session from the command line. Multiple
   429   @{verbatim "-e"}'s are evaluated in the given order. Strange things
   430   may happen when errorneous ML code is provided. Also make sure that
   431   the ML commands are terminated properly by semicolon.
   432 
   433   \medskip The @{verbatim "-u"} option is a shortcut for @{verbatim
   434   "-e"} passing ``@{verbatim "use \"ROOT.ML\";"}'' to the ML session.
   435   The @{verbatim "-f"} option passes ``@{verbatim
   436   "Session.finish();"}'', which is intended mainly for administrative
   437   purposes.
   438 
   439   \medskip The @{verbatim "-m"} option adds identifiers of print modes
   440   to be made active for this session. Typically, this is used by some
   441   user interface, e.g.\ to enable output of proper mathematical
   442   symbols.
   443 
   444   \medskip Isabelle normally enters an interactive top-level loop
   445   (after processing the @{verbatim "-e"} texts). The @{verbatim "-q"}
   446   option inhibits interaction, thus providing a pure batch mode
   447   facility.
   448 
   449   \medskip The @{verbatim "-I"} option makes Isabelle enter Isar
   450   interaction mode on startup, instead of the primitive ML top-level.
   451   The @{verbatim "-P"} option configures the top-level loop for
   452   interaction with the Proof General user interface, and the
   453   @{verbatim "-X"} option enables XML-based PGIP communication.
   454 
   455   \medskip The @{verbatim "-T"} or @{verbatim "-W"} option makes
   456   Isabelle enter a special process wrapper for interaction via
   457   Isabelle/Scala, see also @{file
   458   "~~/src/Pure/System/isabelle_process.scala"}.  The protocol between
   459   the ML and JVM process is private to the implementation.
   460 
   461   \medskip The @{verbatim "-S"} option makes the Isabelle process more
   462   secure by disabling some critical operations, notably runtime
   463   compilation and evaluation of ML source code.
   464 *}
   465 
   466 
   467 subsubsection {* Examples *}
   468 
   469 text {*
   470   Run an interactive session of the default object-logic (as specified
   471   by the @{setting ISABELLE_LOGIC} setting) like this:
   472 \begin{ttbox}
   473 isabelle-process
   474 \end{ttbox}
   475 
   476   Usually @{setting ISABELLE_LOGIC} refers to one of the standard
   477   logic images, which are read-only by default.  A writable session
   478   --- based on @{verbatim HOL}, but output to @{verbatim Test} (in the
   479   directory specified by the @{setting ISABELLE_OUTPUT} setting) ---
   480   may be invoked as follows:
   481 \begin{ttbox}
   482 isabelle-process HOL Test
   483 \end{ttbox}
   484   Ending this session normally (e.g.\ by typing control-D) dumps the
   485   whole ML system state into @{verbatim Test} (be prepared for more
   486   than 100\,MB):
   487 
   488   The @{verbatim Test} session may be continued later (still in
   489   writable state) by:
   490 \begin{ttbox}
   491 isabelle-process Test
   492 \end{ttbox}
   493   A read-only @{verbatim Test} session may be started by:
   494 \begin{ttbox}
   495 isabelle-process -r Test
   496 \end{ttbox}
   497 
   498   \medskip Note that manual session management like this does
   499   \emph{not} provide proper setup for theory presentation.  This would
   500   require @{tool usedir}.
   501 
   502   \bigskip The next example demonstrates batch execution of Isabelle.
   503   We retrieve the @{verbatim Main} theory value from the theory loader
   504   within ML (observe the delicate quoting rules for the Bash shell
   505   vs.\ ML):
   506 \begin{ttbox}
   507 isabelle-process -e 'Thy_Info.get_theory "Main";' -q -r HOL
   508 \end{ttbox}
   509   Note that the output text will be interspersed with additional junk
   510   messages by the ML runtime environment.  The @{verbatim "-W"} option
   511   allows to communicate with the Isabelle process via an external
   512   program in a more robust fashion.
   513 *}
   514 
   515 
   516 section {* The Isabelle tool wrapper \label{sec:isabelle-tool} *}
   517 
   518 text {*
   519   All Isabelle related tools and interfaces are called via a common
   520   wrapper --- @{executable isabelle}:
   521 
   522 \begin{ttbox}
   523 Usage: isabelle TOOL [ARGS ...]
   524 
   525   Start Isabelle tool NAME with ARGS; pass "-?" for tool specific help.
   526 
   527 Available tools:
   528   \dots
   529 \end{ttbox}
   530 
   531   In principle, Isabelle tools are ordinary executable scripts that
   532   are run within the Isabelle settings environment, see
   533   \secref{sec:settings}.  The set of available tools is collected by
   534   @{executable isabelle} from the directories listed in the @{setting
   535   ISABELLE_TOOLS} setting.  Do not try to call the scripts directly
   536   from the shell.  Neither should you add the tool directories to your
   537   shell's search path!
   538 *}
   539 
   540 
   541 subsubsection {* Examples *}
   542 
   543 text {* Show the list of available documentation of the Isabelle
   544   distribution:
   545 
   546 \begin{ttbox}
   547   isabelle doc
   548 \end{ttbox}
   549 
   550   View a certain document as follows:
   551 \begin{ttbox}
   552   isabelle doc system
   553 \end{ttbox}
   554 
   555   Query the Isabelle settings environment:
   556 \begin{ttbox}
   557   isabelle getenv ISABELLE_HOME_USER
   558 \end{ttbox}
   559 *}
   560 
   561 end