arg_val( )

The ARG_VAL( ) function returns a specified argument from the command line that invoked the current 4GL application program. It can also return the name of the current 4GL program.

ARG_VAL () takes an ordinal as its argument.  This should be a positive integer expression that is no higher that the number of arguments in the program. (You can use the NUM_ARGS( ) function to determine how many arguments follow the program name on the command line.)

Usage

This function provides a mechanism for passing values to the 4GL program through the command line that invokes the program. You can design a 4GL program that expects or allows arguments to appear in the command line, after the program name.

You can use the ARG_VAL() function to pass values to MAIN, which cannot have its own formal arguments.  ARG_VAL( ) can be called from any part of the program, not just the MAIN statement.

You can use ARG_VAL( ) to retrieve individual arguments during program execution. 

If 1 ≤ ordinal = n, ARG_VAL(n) returns the n^th command-line argument, as a character string. The value of ordinal must be between zero and the value returned by NUM_ARGS ( ), the number of command-line arguments.

Using ARG_VAL( ) with NUM_ARGS( )

The built-in ARG_VAL( ) and NUM_ARGS( ) functions can pass data to a compiled 4GL program from the command line that invoked the program.

For example, suppose that the 4GL program called program_arguments can accept one or more account names as command-line arguments (in order to process account reports).

program_arguments St MegaSoft01 Querix02 Provia03

In either case, statements in the following program fragment use the ARG_VAL( ) function to store in an array of CHAR variables all the names that the user who invoked program_arguments entered as command-line arguments:

MAIN

  DEFINE

    args ARRAY[8] OF CHAR(10),

    i, line_disp SMALLINT,

    str_disp char(50)                         

  FOR i = 1 TO NUM_ARGS()

    LET args[i] = ARG_VAL(i)

  END FOR

LET str_disp = "Total Number of passed arguments: ", NUM_ARGS()

  DISPLAY str_disp at 2, 5

  FOR i = 1 TO NUM_ARGS()

    LET line_disp = i + 5

    LET str_disp = "Argument " , i,  " was ", args[i]

    DISPLAY str_disp at line_disp , 5

  END FOR

 call fgl_getkey()

END MAIN

After program_arguments is invoked by these command-line arguments, the NUM_ARGS( ) function returns the value 3. Executing the LET statements in the FOR loop assigns the following values to elements of the args array.

Related articles:

Multiple Parameters

num_args()