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Astronomical Data Analysis Software and Systems VII
ASP Conference Series, Vol. 145, 1998
R. Albrecht, R. N. Hook and H. A. Bushouse, e
Ö Copyright 1998 Astronomical Society of the Pacific. All rights reserved.
ds.
GUI­fying and Documenting your Shell Script
Peter. J. Teuben 1
Astronomy Department, University of Maryland, College Park, MD
20742, Email: teuben@astro.umd.edu
Abstract.
We describe a simple method to annotate shell scripts and have a
preprocessor extract a set of variables, present them to the user in a
GUI (using Tcl/Tk) with context sensitive help, and run the script. It
then becomes also very easy to rerun the script with di#erent values of
the parameters and accumulate output of di#erent runs in a set of user
defined areas on the screen, thereby generating a very powerful survey
and analysis tool.
1. Introduction
Scripting languages have often been considered the glue between individual ap­
plications, and are meant to achieve a higher level of programming.
When individual applications are (tightly) integrated into the scripting lan­
guage, this o#ers very powerful scripts, fully graphical user interfaces and a
result sometimes indistinguishable from applications. A recent example of this
is the glish shell in AIPS++ (Shannon 1996). But of course the drawback of this
tight integration is that applications are not always easily accessible to scripts
that do not (or cannot) make use of the environment the scripting language was
meant for.
Apart from the black art of handcoding, one of the traditional methods
to add a GUI to an application is using automatic GUI builders. This has
the advantage that application code and user interaction code are more cleanly
separated, but this sometimes also limits the flexibility with which the code can
be written.
This paper presents a simple implementation where the style of the under­
lying application is batch oriented, and in fact can be written in any language.
The user interface must be cleanly defined in a set of parameters with optional
values (e.g., named ``keyword=value'' pairs). Once the input values have been
set, the application can be launched, results can be captured and presented in
any way the script or application decides.
2. Tcl/Tk: TkRun
The GUI that is created will provide a simple interface to a program that is
spawned by the GUI. This program must have a well defined Command Line
116

GUI­fying and Documenting your Shell Script 117
Interface (CLI), in the current implementation a ``keyword=value'' interface.
Equally well, a Unix­style ``­option value'' could have been used (cf. Appleton's
parseargs package). The GUI builder, a small 600 line C program called tkrun,
scans the script for special tags (easily added as comments, which automatically
make the script self­documenting), and creates a Tcl/Tk script from which the
shell script itself (or any application of choice with a specified CLI) can be
launched (see Figure 2 for a schematic).
The added power one gets with this interface builder is the simplified re­
execution of the script, which gives the user a powerful tool to quickly examine
a complex parameter space of a particular problem.
The input script must define a set of parameters, each with a keyword, an
optional initial value, a widget style, usage requirements and one line help. The
keyword widget style can be selected from a small set of input styles that stan­
dard Tcl/Tk provides (such as generic text entry, file browsers, radio buttons,
sliders etc.)
The current implementation has been tested under Tcl/Tk 7.6 as well as
8.0, but is expected to move along as Tcl/Tk is developed further. For example
a more modern widget layout technique (grid instead of pack) should be used.
Also keywords cannot have dependencies on each other, for example it would be
nice to ``grey out'' certain options under certain circumstances, or allow ranges
of some keywords to depend on the settings of others.
3. Sample Script: testscript
Here is an example header from a C­shell script with which Figure 1 was made.
Note that the script must supply a proper ``keyword=value'' parsing interface,
as was done with a simple foreach construct here. The latest version of tkrun
is available through the NEMO 1 package.
#! /bin/csh ­f
# :: define basic GUI elements for tkrun to extract
#> IFILE in=
#> OFILE out=
#> ENTRY eps=0.01
#> RADIO mode=gauss gauss,newton,leibniz
#> CHECK options=mean,sigma sum,mean,sigma,skewness,kurtosis
#> SCALE n=1 0:10:0.01
# :: some one liners
#> HELP in Input filename
#> HELP out Output filename (should not exist yet)
#> HELP eps Initial (small) step
#> HELP mode Integration Method
#> HELP options Statistics of residuals to show
#> HELP n Order of polynomial
# :: parse named arguments
foreach a ($*)
set $a
end
1 http://www.astro.umd.edu/nemo/

118 Teuben
Figure 1. With the command ``tkrun testscript'' the upper panel
is created, providing a simple interface to the ``key=val'' command line
interface of the script testscript (see below). The lower panel is a
standard Tcl/Tk filebrowser that can be connected to keywords that
are meant to be files. See Figure 2 for a schematic diagram explaining
the interaction between the di#erent programs and scripts.
# :: actual start of code
echo TESTSCRIPT in=$in out=$out eps=$eps mode=$mode options=$options n=$n
# :: legacy script can be inserted here or keyword
# :: values can be passed on to another program
Acknowledgments. I would like to thank Frank Valdes and Mark Pound
for discussing some ideas surrounding this paper, and Jerry Hudson for his
Graphics Command Manager FLO.
References
Appleton, Brad (parseargs, based on Eric Allman's version)

GUI­fying and Documenting your Shell Script 119
#! /bin/csh ­f
#! /bin/wish ­f
#> IFILE
#> ENTRY
# code:
# tags
in=
eps=
RUN
tkrun
testscript
testscript.tk
testscript
exec testscript $args
eps:
lappend args ....
in:
...
...
...
...
testscript in=... out=... eps=... ....
wish ­f testscript.tk
Figure 2. Flow diagram: The command tkrun scans the C­shell
script testscript (top left) for keywords and the Tcl/Tk script
testscript.tk (bottom left) is automatically written and run. It
presents the keywords to the user in a GUI (on the right, see Fig­
ure 1 for a detailed view) ), of which the ``Run'' button will execute
the C­shell code in the script testscript.
Judson, Jerry (FLO: a Graphical Command Manager)
Ousterhout, John, 1994, Tcl and the Tk Toolkit, Addison­Wesley
Shannon, P., 1996, in ASP Conf. Ser., Vol. 101, Astronomical Data Analysis
Software and Systems V, ed. George H. Jacoby & Jeannette Barnes (San
Francisco: ASP), 319
Teuben, P.J., 1995, in ASP Conf. Ser., Vol. 77, Astronomical Data Analysis
Software and Systems IV, ed. R. A. Shaw, H. E. Payne & J. J. E. Hayes
(San Francisco: ASP), 398