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IN SHORT
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This script can be used on Linux to download and install a specified
version of gretl. So for example if you want gretl 2021c, you'll have
to

1 - create a subdirectory where you want to keep the source
2 - copy the "buildgretl" script to that directory
3 - open a terminal and navigate to that directory
4 - type "./buildgretl 2021c" and press Enter

The script will try to download the source code from SourceForge (in
this example, a file called "gretl-2021c.tar.xz"), uncompress it and
compile gretl for you.

After the build is done successfully, you'll be prompted for your
password in order to perform the "make install" stage as root. It is 
assumed that you can use the "sudo" command on your system (it is 
highly inadvisable to run this script as root).

Once installation is complete, you may delete the source if you want
(both the tarball and the directory with the source files).

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MORE DETAILS
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* Options
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By default, the script will try to download the source tarball from
SourceForge by using the "wget" utility, that you should have on your
system already; if you want to skip this step, use the "-d"
option. The script will then assume that a file called
"gretl-2021c.tar.xz" already exists. Also, the script will run a
parallel build to speed things up, but this will somehow hog your
CPU. If you want to disable parallel building, use the "-p" option.

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* Build dependencies
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It is assumed that your system has all build dependencies installed. 
On generic linux system, this includes the gcc compiler and a large 
number of other packages.

On deb-based systems (Debian, Ubuntu, Mint), you can run

sudo apt build-dep gretl

if you need to install the build dependencies. Running this command
may be a good idea anyway, because it will install for you newer
versions of the building tools if available.  Note that, in order to
run the above, you should have the "source repositories" enabled on
your system, which are NOT by default on stock Ubuntu/Mint installs.
If you get a TeX error message complaining about "fancyvrb" not being
found, you may also need to install the "texlive-latex-extra" package.

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* Configure options
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By default, gretl will be build with ODBC support, limited verbosity
and all the optimization options that the configure script can
automatically find (such as AVX support and such). MPI support will be
present if the required dependencies are met. If you want to tweak
that, you're on your own. Specifically, note that the TeX source file
to the manuals will be part of the download (under the doc/tex
subdoirectory) but the pdf manual will NOT be built.

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* Missing icons/function packages etc
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In some cases, running the procedure may give you an installation of
gretl that works perfectly well, apart from a few things being missing
from the GUI client, such as for example some of the icons in the main
window. There are good chances that this is due to stale configuration
files. If this is the case, you could remove the ".gretl2rc" hidden
file and the ".gretl" hidden subdirectory from your HOME dir. This,
however, will cause all the settings to go back to their default
values, and you may have to reinstall some of your function packages.

