2.6. Batch

Batch processing is an effective way to automate repetitive tasks. All of the main display and processing functions can be saved in a batch file to be used later. The batch file is written in ASCII text format, and can be easily edited. Variables, if-then statements, for-next loops, and goto-label jumps can be used in a batch file.

2.6.1. Creating and using batch files

To create a batch file, select Batch Record from the menu. You will be asked to give a filename to the batch file. After this, each WinDisp3.5 command that you execute will be saved to the batch file. When you are finished recording, select Batch Stop in the menu.

These commands can now be executed again by selecting Batch Play and specifying the name of the file.

To see what the batch file looks like, and to make changes to it, use Batch Edit.

If you want to execute the commands one at a time, use Batch Debug; with this option you can also change parameters in each step before executing them. See the example at the left.

2.6.2. Batch file format

The basic format for a command in a batch file is:

Function, "Parameters"

where Function is the menu command and "Parameters" are the parameters associated with this command. The "Parameters" are listed, separated by commas, in the same order as in the dialog box corresponding to the menu command.

For example, a command to display an image might look like this:

File Open Image, " c:\ccd_af\1997\Dc97073.af,,c:\data\projects\c.clr, 88,174,341,401"

It is important to note:

• The option function is effected by the case of the letters used
• Blank lines can be used to separate groups of commands and do not have an effect on the execution
• Spaces and tabs at the beginning of a line are ignored and can be used to separate groups of commands
• Long commands can be written on several lines. The beginning and end of a command is designated by quotation marks.
• Variables are delimited on each side by % symbols. If you place one variable after another, it is necessary to use two symbols between them. Ex. %var1%%var2%

2.6.3. Using variables

Repetitive tasks can be simplified by using variables in a batch file. For example, dekad images (every 10 days) can be given file names similar to the one shown on the previous page (dc97073.af), substituting variables for the month and dekad. The month and dekad will be stored as variables and used to specify the correct file name.
The user will then be prompted to enter the number of the month and dekad for the image desired. The responses will be read into the batch file to identify the image to display.

The dialog would look like this:

Batch Variable Prompt, "Month, Enter month desired, 7"
Batch Variable Prompt, "Dekad, Enter dekad desired, 3"
File Open Image, "c:\ccd_af\1997\Dc97%Month%%Dekad%.af,,c:\data\projects\c.clr, 0,0,0,0"

After replacing the variables by the values attributed to them, (%Month% by 07 and %Dekad% by 3), the command line becomes:

File Open Image, "c:\ccd_af\1997\Dc97073.af,,c:\data\projects\c.clr, 0,0,0,0"

The open file can now be used to display the desired image.

It is important to note:

• If you include variables in a parameter during Batch Record, the command is saved to the batch file.
• Variables can be assigned values within the batch file using Batch Variables Set and with Batch For Begin.
• If you include a variable in a batch but do not set its value, you will automatically be asked for a value during execution.
• With Batch Variable Set you can use algebraic expressions and include other variables in the expression.

2.6.4. If-then statements

With the command Batch If, an if-then statement can be used in a batch file as an error check, and allows the user to validate values for the variables. In programming procedures the commands of an if-then statement are indented to improve the readability.

Batch If Begin, "(%Dekad% > = 1) & (%Dekad% < = 3)"

File Open Image, " c:\ccd_af\1997\Dc97%Month%%Dekad%.af,,c:\data\projects\c.clr, 0,0,0,0"

Batch If Else

File Open Image, "c:\ccd_af\1997\default.img,,c:\data\projects\c.clr, 0, 0, 0, 0"

Batch If End

The example above is an if-then clause delimited by the commands Batch If Begin and Batch If End. Here the variable %Dekad% is used to select the image that will be loaded. The first line checks that the value attributed to this variable is between 1 and 3. If the value is valid, the following line is executed by WinDisp3.5, and Batch If Else is not executed. If the value is not valid, the Batch If Else is executed.

This statement can be useful in automatically adapting names of variables when an error is detected as in section 2.6.3. For example, if the variable %Month% must contain two digits to be valid, but the user enters only one digit (1 to 9 for the months January to September), the if-then statement will place a 0 before the digit to correct the entry:

Batch If Begin, "%Month%<10"

Batch Variable Set, "MonthOK, 0%Month%"

Batch If Else, ""

Batch Variable Set, "MonthOK, %Month%"

Batch If End, ""

After this evaluation, the variable %Month% is replaced by the variable %MonthOK% in the batch file and program processing.

With the help of if-then statements, expressions to evaluate variables can be written in a batch file. Some of the frequently used symbols are used in the following example:

Batch If Begin,"((%Dekad1%=1) & (Dekad2%=3)) | (%Month1%=%Month2%)"
...
Batch If End

Batch processing permits the execution of the command only if the variables %Dekad1% and %Dekad2% are equal to 1 and 3 respectively, or if the variable %Month1% is equal to the variable %Month2%. You will find a list of the symbols used in expressions of this type in section 2.6.8.

It is important to note:

• A special function @file ("name of file") can be put into an if-then statement to insure the existence of a file.
• An if-then expression may contain any kind of numeric character or space.
• The section Batch If Else is not absolutely required in an if-then statement, which can therefore function without execution by default.

2.6.5. For-next loops

To repeat the same command for a series of files (for example, the same type of image for different dates) the for-next loop can be adapted. The example below shows how a for-next loop is used to display images of three consecutive dekads:

Batch For Begin, "Dekad, 1, 3, 1"
File Open Image, " c:\ccd_af\1997\Dc97%Month%%Dekad%.af,,c:\data\projects\c.clr, 0,0,0,0"
Batch For End

The part "Dekad, 1, 3, 1" signifies that the loop is repeated from the value of 1 to the value of 3, increasing successively by 1, and that these values are assigned to the variable %Dekad%. This variable is then used in the command to display the image.

Note that in for-next loops the value of the increment (the last parameter in the Batch For Begin line), can be negative, allowing you to have a command like the following:

Batch For Begin, "Dekad, 3, 1, -1"
....
Batch For End

This loop will load successively the dekad images from 3 to 1. The command executes the loops diminishing the value of the variable.

WinDisp3.5 can execute loops placed within loops as well as within if-then statements.
For example:

Batch For Begin, "LoopOut, 1, 5, 1"
Batch For Begin, "LoopIn, 1, 10, 1"
....
Batch For End
Batch For End

In this example LoopIn is included in LoopOut. As in the previous examples, indenting these commands improve the legibility.

2.6.6. Goto Label jumps

In certain cases, you will want to go from one location to another within a batch. A simple example would be if you ask the user if he wants to repeat the batch and display another image. The batch would resemble the following:

Batch Goto Name, "Loop_begin"
....
....
Batch Variable Set, "Repeat to display another image? (y/n), n"
Batch If Begin, ""%Repeat%" = "y""
Batch Label Goto, "Loop_Begin"
Batch If End

2.6.7. Batch files calling batch files

WinDisp3.5 is capable of calling up one batch from another. Simply save a Batch Play command within a batch, and this batch will execute the other. For example, the following batch executes Mybatch.cmd, then requires the user to rerun the batch a second time:

Batch Label Define "Call_Start"
Batch Play "mybatch.cmd"
Batch Variable Prompt, "UserInput, Run mybatch again?, n"
Batch If Begin ""%UserInput%"="y"
Batch Label Goto, "Call_Start"
Batch If End

It is important to note:

• All the variables in a batch are global, which means that all the variables created and used in a batch can also be used by the file that runs it, and by all the files the batch calls.
• A batch can call itself, but there is a risk of getting into an infinite loop.
• The jumps are not global and cannot be used from one batch to another.

2.6.8. Operators used in batch language

Parentheses must delimit each expression.