Variable update action with a field variable

Using a Variable update action to update a field variable is a convenient way of reading the contents of a 3270 or 5250 field in the host terminal and storing the field's contents as a string into a variable.

A field variable is a type of string variable. A field variable is defined in the <vars> element of the macro script but does not take an initial value. The following contains an example of a field variable.

<vars>
<create name=$intUpdate$" type="integer" value="3"/>
<create name="$strData$" type="string" value="'hello'"/>
<create name="$fieldVar$" type="field" />
</vars>

A field variable contains a string, just as a string variable does, and you can use a field variable in any context in which a string variable is valid. However, a field variable differs from a string variable in the way in which a string is stored into the field variable. The string that a field variable contains is always a string that the macro runtime has read from a 3270 or 5250 field in the current host terminal.

When you use the Variable update action to update a string variable, you specify the following information:
  • The name of the field variable, such as $fldTmp$.
  • A location string, such as '5,11'. (A location string is a string containing two integers separated by a comma that represent a row and column location on the host terminal.)
When the macro runtime performs the Variable update action, the macro runtime:
  1. Recognizes that the variable is a field variable.
  2. Looks at the location string that is to be used to update the field variable.
  3. Finds in the current host terminal the row and column location specified by the location string.
  4. Finds in the current host terminal the 3270 or 5250 field in which the row and column location occurs.
  5. Reads the entire contents of the 3270 or 5250 field, including any leading and trailing blanks.
  6. Stores the entire contents of the field as a string into the field variable.
You can then use the field variable in any context in which a string is valid. For example, you can concatenate the field variable with another string, as in the following: 
'The field\'s contents are'+ $fldPrintOption$
As an example, suppose that the host terminal contains a 3270 or 5250 field with the following characteristics:
  • It begins at row 5, column 8
  • It ends at row 5, column 32
  • It contains the string 'Print VTOC information'
You set up a Variable update action with the following values:
  • In the variable name field you type the name of a field variable that you have just created, $fldData$.
  • In the value field you type a location string, '5,11'. Notice that you have to specify only one row and column location, and that it can be any row and column location that lies within the field.
When the macro runtime performs this Variable update action, the macro runtime reads the entire contents of the field and stores the contents as a string into $fldData$. The field variable $fldData$ now contains the string 'Print VTOC information'.
Parent topic: Variable update action (<varupdate> element)