Marc's Place

1  CALL
   Transfers control to a labeled subroutine within a command
   procedure.

   Format

     CALL  label [parameter [...]]
 

2  Parameters
 

label

   Specifies a label of 1 to 255 alphanumeric characters that
   appears as the first item on a command line. A label cannot
   contain embedded blanks. When the CALL command is executed,
   control passes to the command following the specified label.

   The label can precede or follow the CALL statement in the
   current command procedure. A label in a command procedure must
   be terminated with a colon (:).  Labels for subroutines must be
   unique.

   Labels declared in inner procedure levels are inaccessible from
   outer levels, as in the following example:

   $CALL B
   $SUBROUTINE A
   $  B: SUBROUTINE
   $  ENDSUBROUTINE
   $ENDSUBROUTINE

   In this example, the label B in subroutine A is inaccessible from
   the outer procedure level.
 

parameter [...]

   Specifies from one to eight optional parameters to pass to the
   command procedure. Use quotation marks ("")  to specify a null
   parameter. The parameters assign character string values to
   the symbols named P1, P2, and so on in the order of entry, to a
   maximum of eight. The symbols are local to the specified command
   procedure. Separate each parameter with one or more spaces.

   You can specify a parameter with a character string value
   containing alphanumeric or special characters, with the following
   restrictions:

   o  The command interpreter converts alphabetic characters to
      uppercase and uses blanks to delimit each parameter. To pass a
      parameter that contains embedded blanks or lowercase letters,
      enclose the parameter in quotation marks (" ").

   o  If the first parameter begins with a slash (/),  you must
      enclose the parameter in quotation marks.

   o  To pass a parameter that contains quotation marks and spaces,
      enclose the entire string in quotation marks and use two sets
      of quotation marks within the string. For example:

      $ CALL SUB1 "Never say ""quit"""

      When control transfers to SUB1, the parameter P1 is equated to
      the following string:

      Never say "quit"

      If a string contains quotation marks and does not contain
      spaces, the quotation marks are preserved in the string and
      the letters within the quotation marks remain in lowercase.
      For example:

      $ CALL SUB2 abc"def"ghi

      When control transfers to SUB2, the parameter P1 is equated to
      the string:

      ABCdefGHI

   To use a symbol as a parameter, enclose the symbol in single
   quotation marks (' ')  to force symbol substitution. For example:

   $ NAME = "JOHNSON"
   $ CALL INFO 'NAME'

   The single quotation marks cause the value "JOHNSON" to be
   substituted for the symbol 'NAME'. Therefore, the parameter
   "JOHNSON" is passed as P1 to the subroutine INFO.
 

2  Qualifier
 

/OUTPUT

      /OUTPUT=filespec

   Writes all output to the file or device specified. By default,
   the output is written to the current SYS$OUTPUT device and the
   output file type is LIS. System responses and error messages
   are written to SYS$COMMAND as well as to the specified file. If
   you specify /OUTPUT, the qualifier must immediately follow the
   CALL command. The asterisk (*) and the percent sign (%) wildcard
   characters are not allowed in the output file specification.

   You can also redefine SYS$OUTPUT to redirect the output from a
   command procedure. If you place the following command as the
   first line in a command procedure, output will be directed to the
   file you specify:

   $ DEFINE SYS$OUTPUT filespec

   When the procedure exits, SYS$OUTPUT is restored to its original
   equivalence string. This produces the same result as using the
   /OUTPUT qualifier when you execute the command procedure.
 

2  Example

 $
 $! CALL.COM
 $
 $! Define subroutine SUB1
 $!
 $ SUB1: SUBROUTINE
    .
    .
    .
 $ CALL SUB2 !Invoke SUB2 from within SUB1
    .
    .
    .
 $ @FILE  !Invoke another procedure command file
    .
    .
    .
 $ EXIT
 $ ENDSUBROUTINE !End of SUB1 definition
 $!
 $! Define subroutine SUB2
 $!
 $ SUB2: SUBROUTINE
    .
    .
    .
 $ EXIT
 $ ENDSUBROUTINE !End of SUB2 definition
 $!
 $! Start of main routine. At this point, both SUB1 and SUB2
 $! have been defined but none of the previous commands have
 $! been executed.
 $!
 $ START:
 $ CALL/OUTPUT=NAMES.LOG SUB1 "THIS IS P1"
    .
    .
    .
 $ CALL SUB2 "THIS IS P1" "THIS IS P2"
    .
    .
    .
 $ EXIT  !Exit this command procedure file

     The command procedure in this example shows how to use the
     CALL command to transfer control to labeled subroutines. The
     example also shows that you can call a subroutine or another
     command file from within a subroutine. The CALL command invokes
     the subroutine SUB1, directing output to the file NAMES.LOG
     and allowing other users write (W) access to the file. The
     subroutine SUB2 is called from within SUB1. The procedure
     executes SUB2 and then uses the @ (execute procedure) command
     to invoke the command procedure FILE.COM. When all the commands
     in SUB1 have executed, the CALL command in the main procedure
     calls SUB2 a second time. The procedure continues until SUB2
     has executed.

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