3 Invoking the Program

3.1 Examples

Our first example program shows how to call the gtkdialog from a BASH script.

#! /bin/bash

export MAIN_DIALOG='
 <vbox>
  <text>
    <label>This is a label...</label>
  </text>
  <hbox>
   <button ok></button>
   <button cancel></button>
  </hbox>
 </vbox>'

gtkdialog --program MAIN_DIALOG

This example uses a very plain way to open a dialog box. We store the description of the dialog box in the MAIN_DIALOG environment variable which is exported to the child processes with the BASH export built-in. Then we call the gtkdialog program with the --program option which is followed by the name of the variable holding the dialog box description. It is simple and easy to write BASH scripts in this manner.

A similar calling method can be used when user input is needed. The gtkdialog send the state of the widgets to the standard output when exiting and this is how we can get user input for the BASH program. The next example code show the reading process.

#! /bin/bash

export DIALOG='
<vbox>
  <entry>
    <variable>ENTRY</variable>
  </entry>
  <hbox>
    <button ok></button>
    <button cancel></button>
  </hbox>
</vbox>'

I=$IFS; IFS=""
for STATEMENTS in  $(gtkdialog --program DIALOG); do
  eval $STATEMENTS
done
IFS=$I

if [ "$EXIT" = "OK" ]; then 
  echo "You entered: $ENTRY."
else
  echo "You pressed the Cancel button."
fi

In the example script we use the for built-in to go through the list gtkdialog produced. Changing the field separator (IFS) is a little bit disturbing but necessary since this is the only way to protect the space characters in user input.

In larger software projects it may be a good idea to break the code to separate files. Since gtkdialog can read the description program from file it is easy to write self executable programs with it. This is how the next example constructed.

#! /usr/local/bin/gtkdialog -f
<vbox>
  <checkbox>
    <label>This is a checkbox</label>
    <variable>CHECK1</variable>
  </checkbox>
  <checkbox>
    <label>Another one</label>
    <variable>CHECK2</variable>
  </checkbox>
  <button>
    <label>OK</label>
  </button>
</vbox>

When used in this fashion the state of the widgets can get from the standard output of the script as usually.