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Scripts

You can create script files to execute series and combinations of scripting commands to meet specific needs. When working with scripts, keep in mind the following.

• When creating scripts, each commented line must start and end with the pound (or number) sign (#).
• Scripts must use ANSI coding. Do not use Unicode or other formats.
• Variables can be used in commands to replace items that vary such as machine names. A variable name must start with the dollar sign ($) character and can contain letters or numbers. Values are assigned to variables using the equals (=) assignment statement. For example, valid variable assignment statements are $MySource=alpha; and $MyPassword="pass word";.
• All commands return values which can also be assigned to variables. For example, the connection command returns a connection ID for the connection being created. The statement $ConnectionID=CONNECT dataset to target; saves the connection ID as a variable. The variable components of the connect command could be replaced as well. For example, $TheRepset="DataFiles";, $TheTarget=beta;, and $ConnectionID=CONNECT $TheRepset to $TheTarget; are all valid statements.
• Scripts can take advantage of four flow control programming constructs.

• IF conditional—The IF conditional expression is a comparison between two values or variables. Use the following syntax for an IF conditional.

  IF <relational_expression> THEN <statement_block> [ ELSE <statement_block> ] END

  Use the following conditions to create the relational expression.

  • equal to =
  • not equal to !=
  • less than <
  • less than or equal to <=
  • greater than >
  • greater than or equal to >=
  • statement block—any sequence of valid commands

• FOR Loop—The FOR loop sets a variable to a start value, executes each statement in the statement block, and then adds the step value to the variable. If the new value of the variable does not exceed the end value then the statements will be executed again. This continues until the variable exceeds the end value. If a step value is not provided, the default adds one to the variable. Use the following syntax for the FOR loop.

  FOR <variable> = <start_value> TO <end_value> [STEP <step_value>] DO <statement_block> END

• WHILE Loop—The WHILE loop evaluates a relational expression and, if it is true, then the statement block is executed. When the statement block has completed execution, the expression will be reevaluated again and, if it is true, the statement block is executed again. This continues until the expression is false. Use the conditions specified in the IF conditional to create the relational expression and the following syntax for the WHILE loop.

  WHILE <relational_expression> DO <statement_block> END

• WRITE Command—The WRITE command writes values to the screen. These values can be variables or constants of type integer$, string$, date$, or time$. The write command is used in conjunction with either the IF conditional, WHILE loop, or FOR loop.
• Each command and assignment must end with a semi-colon. However, no semicolon is necessary after the END keyword for the IF conditional and the loop statements.

• When using the Command Line client, a script file can be executed using the -f option. Create a one-line batch file using the following command to initiate the Command Line client with the -f option and specify the name of the script to execute.

  DTCL -f /directory_name/script_name

  If you do not specify a path for the script file, Double-Take Availability will look in the directory where the DTCL -f command was executed.

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