INSTALL.txt

ISIS Installation Guide
=======================
John C. Houck <houck&#64;space&#46;mit&#46;edu>
{backend@xhtml11:Last updated\: {revdate}}

For more information about isis, see: http://space.mit.edu/cxc/isis/

Send bug reports, comments and suggestions to:
isis-users@space.mit.edu

Overview
--------
*****************************************************************
The easiest way to set up a new isis installation is to run an
installation script that will automatically download and
install isis and a few commonly used modules. This installation
method is documented in Part I, <<XI,Scripted Installation>>.

For those who prefer greater control and customization, full details
of the isis installation process are documented in Part II,
<<XII,Manual Installation>>.

Once isis is installed, a number of optional components are
available to support a variety of specialized tasks.  For
details, see Part III, <<XIII,Optional Components>>.
*****************************************************************

[[XI]]
I. Scripted Installation
------------------------
This installation method is intended to simplify the most
common situation in which isis is being installed for use as a
spectral analysis tool with support for using the XSPEC
spectral model library.

*For The Impatient:* assuming certain requirements are met, the
following steps should be sufficient to install isis into
directory 'DIR':
..........................................................
   wget http://space.mit.edu/cxc/isis/install-isis.sh
   setenv HEADAS /usr/local/headas/x86_64-unknown-linux-gnu-libc2.7/
   sh install-isis.sh DIR
..........................................................
If reading instructions just isn't for you, then by all means
go ahead and try that now, substituting the +HEADAS+ path
appropriate for your system.

The next section explains the process and requirements in a
little more detail.

Requirements
~~~~~~~~~~~~
Before running the installation script, the following programs
must be available on your system:

- +wget+
- +tar+
- +make+
- C compiler (eg. +gcc+)
- Fortran compiler (eg. +gfortran+)

See below for <<Xa,advice>> on choosing C and Fortran compilers.

To verify that each of these programs is available on your
command search path, use +which+:
................
    > which wget
    /usr/bin/wget
................

The simplest way to obtain the XSPEC spectral model library is
to install XSPEC itself.  Isis also uses the +cfitsio+ and
+pgplot+ libraries that come with XSPEC. For these reasons, the
isis installation script assumes that XSPEC has been installed
on your system; XSPEC is available from: +
   http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/

When installing XSPEC, we strongly recommend compiling it from
source code.

Installation
~~~~~~~~~~~~
Once the above requirements are satisfied, isis installation
can proceed as follows:

. Move to a working directory where you have at least 200 MB of
space to download and compile the software, then download the
isis installation script into that directory:
+
.....................................................................
   cd isis-src
   wget http://space.mit.edu/cxc/isis/install-isis.sh
.....................................................................

. Set the +HEADAS+ environment variable to provide the path
to your XSPEC installation.  To set it, (t)csh users should
type something like:
+
.....................................................................
   setenv HEADAS /usr/local/headas/x86_64-unknown-linux-gnu-libc2.7/
.....................................................................
+
while users of bash, ksh, etc.. should type something like
+
.........................................................
   HEADAS=/usr/local/headas/x86_64-unknown-linux-gnu-libc2.7/
   export HEADAS
.........................................................

. Set any compiler environment variables 'CC', 'CFLAGS', 'FC',
'FFLAGS', and 'LDFLAGS' necessary to properly define your
build environment (*<<Xmac, Important Note for Mac Users>>*).

. Run the installation script to install everything into
directory 'DIR'
+
..........................
   sh install-isis.sh DIR
..........................
+
If no directory 'DIR' is provided on the script command line,
then everything will be installed into the current directory.

If all goes well, the script will download, compile and install
isis along with a few commonly used modules.  When the script
finishes, it will provide the path to the isis executable, e.g.
'DIR/bin/isis'. When you run isis, you should see something
like this:

............................................................
> DIR/bin/isis

Welcome to ISIS Version 1.6.2
Copyright (C) 1998-2016 Massachusetts Institute of Technology

          Isis web page: http://space.mit.edu/cxc/isis/
   Mailing list archive: http://space.mit.edu/cxc/isis/archive/
 Send questions to the mailing list: <isis-users@space.mit.edu>.
     For a summary of recent changes, type:  "help changes"

isis>
............................................................

To run isis by typing 'isis' at the unix command prompt instead
of 'DIR/bin/isis', consider adding the 'DIR/bin' directory to
your command search path. Alternatively, you might consider
putting an appropriate symbolic link into a bin directory
that's already on your path. For example, if '$HOME/bin' is on
your command search path, consider putting a symbolic link
there:
.....................................
    ln -s DIR/bin/isis $HOME/bin/isis
.....................................

Now that isis is working, you may want to consider installing
some of the optional software mentioned in <<XIII,Part III>>.

[[XII]]
II. Manual Installation
-----------------------
The manual installation method is available for those
who want more control over the installation process.

Requirements
------------
=======================================================================
The S-Lang library is required (version 2.2.4 or newer).
This library is available from: +
  http://www.jedsoft.org/slang/

To build isis with support for fitting XSPEC spectral models,
the XSPEC spectral model library must be installed somewhere on
your system.  This library is part of HEASoft, which is available
from: +
   http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/

Along with the spectral model library, the HEASoft installation
also provides the cfitsio and pgplot libraries; if you choose
not to install HEASoft, then cfitsio and pgplot must be
installed.
=======================================================================

Table of Contents
-----------------

. <<X1,Installing from source code>>
  a. <<Xa,Choosing compilers>>
  b. <<Xb,Recommended installation method>>
  c. <<Xc,INSTALLATION EXAMPLE>>
  d. <<Xd,Configure options>>
  e. <<Xe,(optional) Installing modules>>
. <<X2,Installation suggestions for specific architectures>>
  - <<Xlinux,Linux>>
  - <<Xmac,Mac OS X>>
  - <<Xsolaris,Solaris>>
. <<X3,TROUBLESHOOTING>>

[[X1]]
1. Installing from source code
-------------------------------

[[Xa]]
a. Choosing compilers
~~~~~~~~~~~~~~~~~~~~
It is important to build isis and S-Lang using the same C and
Fortran compilers that were used to build XSPEC. For this
reason, the HEASoft compiler recommendations also apply to
isis.  For details, see:

http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/supported_platforms.html

http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/install.html

Ideally, your C and Fortran compilers should be part of a
matched set and their version numbers should match exactly.
For example, using the C compiler 'gcc' and the Fortran
compiler 'gfortran', one can check the version numbers like so:

.................................................................
  > gcc --version
  gcc (Debian 4.3.2-1.1) 4.3.2

  > gfortran --version
  GNU Fortran (Debian 4.3.2-1.1) 4.3.2
.................................................................

The compilers shown in this example are likely to be compatible
because they have the same version number and because they came
from the same Linux distribution (Debian).

To specify which compilers to use when building isis, set the
+CC+ and +FC+ environment variables.  For example, to set these
environment variables, (t)csh users should type:

.................................................................
  setenv CC gcc-4.3
  setenv FC gfortran-4.3
.................................................................

while bash, ksh, etc. users should type:

.................................................................
  CC=gcc-4.3
  export CC

  FC=gfortran-4.3
  export FC
.................................................................

[[Xb]]
b. Recommended installation method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[IMPORTANT]
=================================================================
Be sure to build isis and S-Lang using the same C and Fortran
compilers that were used to build XSPEC.  If your compilers are
incompatible, the build may fail.
=================================================================

If S-Lang has been installed in a standard location such as
'/usr/local', the isis installation process may be as simple as:

.................................................................
    ./configure --with-headas=$HEADAS
    make
    make check
    make install
.................................................................

The +HEADAS+ environment variable gives the path to your local
HEASoft installation.  To set it, (t)csh users should type
something like:

.................................................................
   setenv HEADAS /usr/local/headas/x86_64-unknown-linux-gnu-libc2.7/
.................................................................

while users of bash, ksh, etc.. should type something like:

.................................................................
   HEADAS=/usr/local/headas/x86_64-unknown-linux-gnu-libc2.7/
   export HEADAS
.................................................................

Note that the exact directory path depends on the details of
your system.

By default, isis files will be installed in '/usr/local/isis'
and a symbolic link to the isis executable will be placed in
'/usr/local/bin/isis'. If '/usr/local/bin' is already in your
command search path then, after isis is installed, you should
be able to run it by typing 'isis' at the unix prompt:

.................................................................
   > isis
.................................................................

To install isis in 'DIR' instead of '/usr/local', include the
'--prefix' configure option:

.................................................................
  --prefix=DIR
.................................................................

If S-Lang has been installed in a non-standard location it may
be necessary to specify its location using the '--with-slang'
configure option:

.................................................................
  --with-slang=DIR
.................................................................

To make use of the APED spectroscopy database, include the
'--with-atomdb' configure option:

.................................................................
  --with-atomdb=DIR
.................................................................

[[Xc]]
c. INSTALLATION EXAMPLE
~~~~~~~~~~~~~~~~~~~~~~~
To step through a complete installation example, suppose that
your compilers are in '/usr/local/bin', you want to unpack the
source code in '/soft/src', and you want to install everything
in '/soft', with HEASoft in '/soft/headas' and isis in
'/soft/isis'.  To create this setup, perform the following
steps:

[NOTE]
=================================================================
To make this example concrete, specific software version
numbers appear in the relevant URLs and command-lines. When
performing a new installation, it is usually best to choose the
newest available version of each package.
=================================================================

. Create the /soft/src directory:
+
.......................
  mkdir -p /soft/src
.......................
+
*****************************************************************
Note that creating this directory requires root permission.
However, it is unwise to compile software as root.  Only the
last step (make install) should be performed as root.

If you do not have root permission and cannot create the
'/soft/src' directory, that's ok, just choose a directory where
you have write permission and enough space to hold all the
files.  The disk space requirement is determined primarily by
the size of HEASoft; S-Lang and ISIS require very little space
in comparison.
*****************************************************************

. Download S-Lang, isis, and HEASoft:
+
S-Lang source code is available from: +
ftp://space.mit.edu/pub/davis/slang/v2.2/
+
ISIS source code is available from: +
ftp://space.mit.edu/pub/cxc/isis/
+
HEASoft source code is available from: +
http://heasarc.gsfc.nasa.gov/lheasoft/download.html
+
After downloading the source code tar files, move the
files to '/soft/src':
+
.................................................................
       mv slang-2.2.4.tar.gz /soft/src
       mv isis-1.6.2.tar.gz /soft/src
       mv heasoft-6.11.1.tar.gz /soft/src
.................................................................

. Specify compilers:
+
In C shell variants, such as csh, tcsh, type:
+
.................................................................
       setenv CC /usr/local/bin/gcc
       setenv FC /usr/local/bin/gfortran
       setenv CXX /usr/local/bin/g++
.................................................................
+
In Bourne shell variants, such as bash, ksh, etc.  type:
+
.................................................................
       CC=/usr/local/bin/gcc
       export CC

       FC=/usr/local/bin/gfortran
       export FC

       CXX=/usr/local/bin/g++
       export CXX
.................................................................

. Install S-Lang:
+
.................................................................
       cd /soft/src
       gunzip -c slang-2.2.4.tar.gz | tar xf -
       cd slang-2.2.4
       ./configure --prefix=/soft
       make
       make install
.................................................................

. Install HEASoft:
+
.................................................................
       cd /soft/src
.................................................................
+
Follow the installation instructions in +
http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/install.html
+
*****************************************************************
Be sure to run the HEASoft configure script with the
appropriate '--prefix' option so that HEASoft will
be installed in the directory chosen for this
example, '/soft/src/headas':
.................................................................
          ./configure --prefix=/soft/src/headas ...
.................................................................
Once HEASoft is installed, the HEADAS environment variable should
be set to
.................................................................
           /soft/src/headas/<platform-string>/
.................................................................
as shown above.
*****************************************************************

. Install isis:
+
.................................................................
       cd /soft/src
       gunzip -c isis-1.6.2.tar.gz | tar xf -
       cd isis-1.6.2
       ./configure --prefix=/soft --with-slang=/soft \
                   --with-headas=$HEADAS
       make
       make check
       make install
.................................................................

At this point, '/soft/bin/isis' should be a symbolic link to the
isis executable.  When you run it, you should see something
like this:
.................................................................
> /soft/bin/isis

Welcome to ISIS Version 1.6.2
Copyright (C) 1998-2016 Massachusetts Institute of Technology

          Isis web page: http://space.mit.edu/cxc/isis/
   Mailing list archive: http://space.mit.edu/cxc/isis/archive/
 Send questions to the mailing list: <isis-users@space.mit.edu>.
     For a summary of recent changes, type:  "help changes"

isis>
.................................................................

Once isis is working, you may want to consider installing
some of the optional software mentioned in <<XIII,Part III>>.

For a complete list of supported configure options, do:
..................................
  ./configure --help
..................................
Many of these configure options are described in the next
section.

[[Xd]]
[glossary]
d. Configure options
~~~~~~~~~~~~~~~~~~~~
--with-prefix=DIR::
    Use this option to install isis files in 'DIR/isis/$version'.

--with-subdir=DIR::
    Use this option to install isis files in '$prefix/isis/DIR'
    instead of '$prefix/isis/$version'.
    If  DIR="" (the empty string) then isis files will be
    installed in '$prefix/isis'.

--with-headas=$HEADAS::
    Use this option to provide the path to the xspec libraries.
    When the cfitsio and pgplot libraries are present in
    '$HEADAS/lib', it is usually best to use them when building
    isis, rather than any other versions of these libraries
    that may be available on your system. For this reason, it
    is usually best to avoid combining the --with-headas option
    with any of the --with-cfitsio or --with-pgplot options.

--with-atomdb=$ATOMDB::
    Use this option to provide the path to the ATOMDB
    spectroscopy database, available from: http://www.atomdb.org/

--with-xspec-version=nn::
    When your local HEASoft installation includes both xspec11
    and xspec12, use this option to specify which version of
    the xspec libraries to link to isis.  If this configure
    option is absent, and both xspec versions are present, isis
    will use xspec12.

--with-xspec-static::
    Use this option to indicate that the xspec libraries should
    be statically linked to the isis executable.

--with-xspec-modelsonly=DIR::
    Use this option to provide the path to your xspec modelsonly
    library installation.  When this option is used, the CCfits
    library must also be installed on your system.  The location
    of the CCfits library should be specified unless the library
    is installed in'$prefix' or another standard location.

--with-local-setup=FILE::
    Use this option to indicate that the S-Lang script in FILE
    should be loaded when isis starts up.  This file can be
    used to define site-local customizations that may be helpful
    for all users at your site.

--with-slang=DIR::
    Use this option to indicate that libslang is in 'DIR/lib'
    and slang.h is in 'DIR/include'

--with-slanglib=LIB_DIR::
--with-slanginc=INC_DIR::
    Use these options to indicate that libslang is in 'LIB_DIR'
    and slang.h is in 'INC_DIR'.  If you use these options,
    do not use the --with-slang option.

--with-cfitsio=DIR::
    Use this option to indicate that libcfitsio is in 'DIR/lib'
    and fitsio.h is in 'DIR/include'.

--with-cfitsiolib=LIB_DIR::
--with-cfitsioinc=INC_DIR::
    Use these options to indicate that libcfitsio is in 'LIB_DIR'
    and fitsio.h is in 'INC_DIR'.  If you use these options,
    do not use the --with-cfitsio option.

--with-pgplot=DIR::
    Use this option to indicate that libpgplot is in 'DIR/lib'
    and cpgplot.h is in 'DIR/include'

--with-pgplotlib=LIB_DIR::
--with-pgplotinc=INC_DIR::
    Use these options to indicate that libpgplot is in 'LIB_DIR'
    and cpgplot.h is in 'INC_DIR'.  If you use these options,
    do not use the --with-pgplot option.

--with-CCfits=DIR::
    Use this option to indicate that libCCfits is in 'DIR/lib'
    and CCfits.h is in 'DIR/include'

--with-CCfitslib=LIB_DIR::
--with-CCfitsinc=INC_DIR::
    Use these options to indicate that libCCfits is in 'LIB_DIR'
    and CCfits.h is in 'INC_DIR'.  If you use these options,
    do not use the --with-CCfits option.

--with-dep=DIR::
    Use this option to indicate that slang and cfitsio are
    installed in 'DIR/lib' and 'DIR/include', and that pgplot is
    installed in 'DIR/pgplot'.

--with-readline[=arg]::
    Use this option to select which readline library to use:
       - arg=gnu means use GNU readline
       - arg=DIR means use GNU readline (from 'DIR/lib' and 'DIR/include')
       - arg=slang means use S-Lang readline only

--with-fclibs="..."::
    Use this option to provide additional libraries that may be
    needed by your compilers, but that are not automatically
    picked up by the configure script.  For example, if you
    choose to compile isis with a C\+\+ compiler (not recommended),
    you may need to use --with-fclibs="-lstdc++".

--x-libraries=DIR/lib::
--x-includes=DIR/include::
    Use these options to indicate that the X libraries and
    include files are installed in 'DIR/lib' and 'DIR/include',
    respectively.

[[Xe]]
e. (optional) Installing modules
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You may wish to install additional isis- or slang-related
software, such as one or more of the modules available from +
http://space.mit.edu/cxc/isis/modules.html.

Such modules should be installed in the same directory tree
where you installed slang, so that S-Lang applications such as
isis will automatically find the new modules.

For example, consider adding the histogram module to the
installation described above, where both isis and slang were
installed in /soft.  To install the histogram module, do the
following:

First, download the module source code tar file from +
http://space.mit.edu/CXC/software/slang/modules/hist/src/

Then, assuming the tar file is in /soft/src, do:
.................................................................
   cd /soft/src
   gunzip -c slhist-0.3.2a.tar.gz | tar xf -
   cd slhist-0.3.2a
   ./configure --prefix=/soft --with-slang=/soft
   make
   make install
.................................................................

The histogram module can then be imported into isis like so:

.................................................................
   isis> require ("histogram");
.................................................................

If you install a module that depends on other libraries (e.g.
libpvm), then those additional libraries may be installed
either in a standard system location (e.g. /usr) or in the same
directory tree as isis (e.g. /soft), depending on which is most
convenient.

[[X2]]
2. Installation suggestions for specific architectures
-------------------------------------------------------

[[Xlinux]]
Linux systems:
~~~~~~~~~~~~~

- Recommended compilers: use gcc-4.3 and gfortran-4.3, or newer.
+
Older compilers will also work, but code compiled by older
versions of gfortran is not fully compatible with newer
versions of gfortran.  On older systems, using gcc-3.4 with
g77 will work; note, however, that g77 is no longer
maintained.

[[Xmac]]
Mac OS X systems:
~~~~~~~~~~~~~~~~

- See http://space.mit.edu/cxc/isis/mac_install.html

[[Xsolaris]]
Solaris systems:
~~~~~~~~~~~~~~~

- The Solaris compilers are preferred:  CC=cc and FC=f90

AIX systems:
~~~~~~~~~~~

- The IBM compilers are preferred:  CC=xlc and FC=xlf

[[X3]]
3. TROUBLESHOOTING
------------------

Answers to some frequently asked questions are available from
the web site: +
http://space.mit.edu/cxc/isis/faq.html

If isis did not compile:
~~~~~~~~~~~~~~~~~~~~~~~~

 - Did you build isis <<Xa,using the same C and Fortran
  compilers>> that were used to build the XSPEC libraries?

 - Are your C and Fortran compilers <<Xa,compatible>>?

[[XIII]]
III. Optional Components
------------------------
=======================================================================
Isis provides extensive support for constructing
multi-component collisional ionization equilibrium spectral
models using the ATOMDB spectroscopy database, available from: +
  http://www.atomdb.org/

A growing collection of modules and data analysis packages is
available from: +
  http://space.mit.edu/cxc/isis/modules.html

The available data analysis packages provide support for timing
analysis, automated processing of Chandra grating data, and
analysis of density-dependent line ratios from He-like triplet
lines.

The available modules provide support for low-level I/O
of FITS and HDF5 files, interaction with the ds9 image viewer,
an interface to the GSL scientific library, 3D visualization,
PVM-based parallel processing, and more.
=======================================================================

Appendix
--------

***********************************************************************
Below, I have attached the generic INSTALL instructions included in the
autoconf distribution.  These instructions provide more detail on how the
configure script works and also describe other installation options which
may be supported by the configure script.
***********************************************************************

Copyright (C) 1994, 1995, 1996, 1999, 2000, 2001, 2002 Free Software
Foundation, Inc.

   This file is free documentation; the Free Software Foundation gives
unlimited permission to copy, distribute and modify it.

Basic Installation
------------------

These are generic installation instructions.

The 'configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation.  It uses
those values to create a 'Makefile' in each directory of the package.
It may also create one or more '.h' files containing system-dependent
definitions.  Finally, it creates a shell script 'config.status' that
you can run in the future to recreate the current configuration, and a
file 'config.log' containing compiler output (useful mainly for
debugging 'configure').

It can also use an optional file (typically called 'config.cache'
and enabled with '--cache-file=config.cache' or simply '-C') that saves
the results of its tests to speed up reconfiguring.  (Caching is
disabled by default to prevent problems with accidental use of stale
cache files.)

If you need to do unusual things to compile the package, please try
to figure out how 'configure' could check whether to do them, and mail
diffs or instructions to the address given in the 'README' so they can
be considered for the next release.  If you are using the cache, and at
some point 'config.cache' contains results you don't want to keep, you
may remove or edit it.

The file 'configure.ac' (or 'configure.in') is used to create
'configure' by a program called 'autoconf'.  You only need
'configure.ac' if you want to change it or regenerate
'configure' using a newer version of 'autoconf'.

The simplest way to compile this package is:

. 'cd' to the directory containing the package's source code and type
'./configure' to configure the package for your system.  If you're
using 'csh' on an old version of System V, you might need to type
'sh ./configure' instead to prevent 'csh' from trying to execute
'configure' itself.
+
Running 'configure' takes awhile.  While running, it prints some
messages telling which features it is checking for.

. Type 'make' to compile the package.

. Optionally, type 'make check' to run any self-tests that come with
the package.

. Type 'make install' to install the programs and any data files and
documentation.

. You can remove the program binaries and object files from the
source code directory by typing 'make clean'.  To also remove the
files that 'configure' created (so you can compile the package for
a different kind of computer), type 'make distclean'.  There is
also a 'make maintainer-clean' target, but that is intended mainly
for the package's developers.  If you use it, you may have to get
all sorts of other programs in order to regenerate files that came
with the distribution.

Compilers and Options
---------------------

Some systems require unusual options for compilation or linking that
the 'configure' script does not know about.  Run './configure --help'
for details on some of the pertinent environment variables.

You can give 'configure' initial values for configuration parameters
by setting variables in the command line or in the environment.  Here
is an example:
....................................................
     ./configure CC=c89 CFLAGS=-O2 LIBS=-lposix
...................................................
See <<X7,Defining Variables>>, for more details.

Compiling For Multiple Architectures
------------------------------------

You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  To do this, you must use a version of 'make' that
supports the 'VPATH' variable, such as GNU 'make'.  'cd' to the
directory where you want the object files and executables to go and run
the 'configure' script.  'configure' automatically checks for the
source code in the directory that 'configure' is in and in '..'.

If you have to use a 'make' that does not support the 'VPATH'
variable, you have to compile the package for one architecture at a
time in the source code directory.  After you have installed the
package for one architecture, use 'make distclean' before reconfiguring
for another architecture.

Installation Names
------------------

By default, 'make install' will install the package's files in
'/usr/local/bin', '/usr/local/man', etc.  You can specify an
installation prefix other than '/usr/local' by giving 'configure' the
option '--prefix=PATH'.

You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.  If you
give 'configure' the option '--exec-prefix=PATH', the package will use
PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.

In addition, if you use an unusual directory layout you can give
options like '--bindir=PATH' to specify different values for particular
kinds of files.  Run 'configure --help' for a list of the directories
you can set and what kinds of files go in them.

If the package supports it, you can cause programs to be installed
with an extra prefix or suffix on their names by giving 'configure' the
option '--program-prefix=PREFIX' or '--program-suffix=SUFFIX'.

Optional Features
-----------------

Some packages pay attention to '--enable-FEATURE' options to
'configure', where FEATURE indicates an optional part of the package.
They may also pay attention to '--with-PACKAGE' options, where PACKAGE
is something like 'gnu-as' or 'x' (for the X Window System).  The
'README' should mention any '--enable-' and '--with-' options that the
package recognizes.

For packages that use the X Window System, 'configure' can usually
find the X include and library files automatically, but if it doesn't,
you can use the 'configure' options '--x-includes=DIR' and
'--x-libraries=DIR' to specify their locations.

Specifying the System Type
--------------------------

There may be some features 'configure' cannot figure out
automatically, but needs to determine by the type of machine the package
will run on.  Usually, assuming the package is built to be run on the
_same_ architectures, 'configure' can figure that out, but if it prints
a message saying it cannot guess the machine type, give it the
'--build=TYPE' option.  TYPE can either be a short name for the system
type, such as 'sun4', or a canonical name which has the form:
............................
     CPU-COMPANY-SYSTEM
............................
where SYSTEM can have one of these forms:
............................
     OS KERNEL-OS
............................
See the file 'config.sub' for the possible values of each field.  If
'config.sub' isn't included in this package, then this package doesn't
need to know the machine type.

If you are _building_ compiler tools for cross-compiling, you should
use the '--target=TYPE' option to select the type of system they will
produce code for.

If you want to _use_ a cross compiler, that generates code for a
platform different from the build platform, you should specify the
"host" platform (i.e., that on which the generated programs will
eventually be run) with '--host=TYPE'.

Sharing Defaults
----------------

If you want to set default values for 'configure' scripts to share,
you can create a site shell script called 'config.site' that gives
default values for variables like 'CC', 'cache_file', and 'prefix'.
'configure' looks for 'PREFIX/share/config.site' if it exists, then
'PREFIX/etc/config.site' if it exists.  Or, you can set the
'CONFIG_SITE' environment variable to the location of the site script.
A warning: not all 'configure' scripts look for a site script.

[[X7]]
Defining Variables
------------------

Variables not defined in a site shell script can be set in the
environment passed to 'configure'.  However, some packages may run
configure again during the build, and the customized values of these
variables may be lost.  In order to avoid this problem, you should set
them in the 'configure' command line, using 'VAR=value'.  For example:

...................................
./configure CC=/usr/local2/bin/gcc
...................................

will cause the specified gcc to be used as the C compiler (unless it is
overridden in the site shell script).

'configure' Invocation
----------------------

'configure' recognizes the following options to control how it
operates.

'--help'::
'-h'::
     Print a summary of the options to 'configure', and exit.

'--version'::
'-V'::
     Print the version of Autoconf used to generate the 'configure'
     script, and exit.

'--cache-file=FILE'::
     Enable the cache: use and save the results of the tests in FILE,
     traditionally 'config.cache'.  FILE defaults to '/dev/null' to
     disable caching.

'--config-cache'::
'-C'::
     Alias for '--cache-file=config.cache'.

'--quiet'::
'--silent'::
'-q'::
     Do not print messages saying which checks are being made.  To
     suppress all normal output, redirect it to '/dev/null' (any error
     messages will still be shown).

'--srcdir=DIR'::
     Look for the package's source code in directory DIR.  Usually
     'configure' can determine that directory automatically.

'configure' also accepts some other, not widely useful, options.  Run
'configure --help' for more details.