DO

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Runs a program or function.

Syntax

DO <filename> | ? | <filename skeleton> |
 <function name>
[WITH <parameter list>]

<filename> | ? | <filename skeleton>

The program file to execute. The ? and <filename skeleton> options display a dialog box from which you can select a file. If you specify a file without including its path, dBASE Plus looks for the file in the current directory, then in the search path in search order. See "Search path and order" later in this section for more information.

If you specify a file without including its extension, dBASE Plus assumes a .PRO extension (a compiled object file). If dBASE Plus can't find a .PRO file, it looks for a .PRG file (a source file), which, if found, it compiles. By default, dBASE Plus creates the .PRO in the same directory as the .PRG, which might not be the current directory.

<function name>

The function name in an open program file to execute. The function must be in the program file containing the DO command that calls it, or in a separate open file on the search path. The search path is described later in this section.

WITH <parameter list>

Specifies memory variable values, field values, or any other valid expressions to pass as parameters to the program or function. See the description of PARAMETERS for information on parameter passing.

Description

Use DO to run program files from the Command window or to run other programs from a program. If you enter DO in the Command window, control returns to the Command window when the program or function ends. If you use DO in a program to execute another program, control returns to the program line following the DO statement when the program ends.

Although you may use DO to execute functions, common style dictates the use of the call operator (the parentheses) when calling functions, and the DO command when running a program file. The DO command supports the use of a file path and extension, and the ? and <filename skeleton> options. The call operator supports calling a function by name only. In the not-recommended situation where you have a program file that has the same name as a function loaded into memory, the DO command will execute the program file, and the call operator will executed the loaded function. Other than these differences, the two calling methods behave the same, and follow the same search rules described later in this section.

You may nest routines; that is, one routine may call another routine, which may call another routine, and so on. This series of routines, in the order in which they are called, is referred to as the call chain.

When dBASE Plus executes or loads a program file, it will automatically compile the program file into object code when either:

There is no object code file, or

SET DEVELOPMENT is ON, and program file is newer than the object code file (the source code file’s last update date and time is later than the object code file’s)

When dBASE Plus encounters a function call in a program file, it looks in that file for a FUNCTION or PROCEDURE of the specified name. If the current program file contains a FUNCTION and a PROCEDURE with the same name, dBASE Plus executes the first one declared. If dBASE Plus doesn't find a FUNCTION or PROCEDURE definition of the specified name in the same program file, it looks for a program file, FUNCTION, or PROCEDURE of the specified name on the search path in search order.

Search path and order

If the name you specify with DO doesn't include a path or a file-name extension, it can be a file, FUNCTION, or PROCEDURE name. To resolve the ambiguity, dBASE Plus searches for the name in specific places (the search path) in a specific order (the search order) and runs the first program or function of the specified name that it finds. The search path and order dBASE Plus uses is as follows:

1. The executing program's object file (.PRO)

• Other open object files (.PRO) in the call chain, in most recently opened order

• The file specified by SYSPROC = <filename> in PLUS.ini

• Any files opened with SET PROCEDURE, SET PROCEDURE...ADDITIVE, or SET LIBRARY statements, in the order in which they were opened

• The object file (.PRO) with the specified name in the search path

• The program file (.PRG) with the specified name in the search path, whichdBASE Plus automatically compiles

The search path is controlled with the SET PATH command. It is not used when you are running a compiled EXE (a deployed application)—all program files must be linked into the executable. All path information is lost during linking and ignored during execution, which means that you cannot have more than one file with the same name, even if they originally came from different directories.

Because program files must be compiled into object code to be linked into a compiled EXE, the last search step, #6, does not apply when running a compiled EXE.