HP OpenVMS DCL Dictionary

@ (Execute Procedure)

Executes a command procedure or requests the command interpreter to read subsequent command input from a specific file or device.

Format

@ filespec [parameter[,...]]

Parameters

filespec
Specifies either the input device or the file for the preceding command, or the command procedure to be executed. The default file type is .COM. The asterisk (*) and the percent sign (%) wildcard characters are not allowed in the file specification.
parameter[,...]
Specifies from one to eight optional parameters to pass to the command procedure. The symbols (P1, P2, ... P8) are assigned character string values in the order of entry. The symbols are local to the specified command procedure. Separate each parameter with one or more blanks. Use two consecutive quotation marks ("") to specify a null parameter. You can specify a parameter with a character string value containing alphanumeric or special characters, with the following restrictions:
The command interpreter converts alphabetic characters to uppercase and uses blanks to delimit each parameter. To pass a parameter that contains embedded blanks or literal lowercase letters, place the parameter in quotation marks.
If the first parameter begins with a slash (/), you must enclose the parameter in quotation marks (" ").
To pass a parameter that contains literal quotation marks and spaces, enclose the entire string in quotation marks and use two consecutive quotation marks within the string. For example, the command procedure TEST.COM contains the following line:
$ WRITE SYS$OUTPUT P1
Enter the following at the DCL prompt ($):
$ @TEST "Never say ""quit"""
When the procedure TEST.COM executes, 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, enter the following at the DCL prompt:
$ @TEST abc"def"ghi
When the procedure TEST.COM executes, the parameter P1 is equated to the following string:

ABC"def"GHI
To use a symbol as a parameter, enclose the symbol in single quotation marks (` ') to force symbol substitution. For example:
$ NAME = "JOHNSON" $ @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 INFO.COM.

Description

Use the @ command to execute a command procedure that contains the following:

DCL command lines or data, or both
Qualifiers or parameters, or both, for a specific command line

To execute a command procedure containing commands or data, or both, place the @ command at the beginning of a command line and then specify the name of the command procedure file. The command procedure can contain DCL commands and input data for a command or program that is currently executing. All DCL commands in a command procedure must begin with a dollar sign ($). If a command is continued with a hyphen (-), the subsequent lines must not begin with a dollar sign.
Any line in a command procedure that does not contain a dollar sign in the first character position (and is not a continuation line) is treated as input data for the command or program that is currently executing. The DECK command allows you to specify that data contains dollar signs in record position one.
A command procedure can also contain the @ command to execute another command procedure. The maximum command level you can achieve by nesting command procedures is 16, including the top-level command procedure. Command procedures can also be queued for processing as batch jobs, either by using the SUBMIT command or by placing a deck of cards containing the command procedure in the system card reader.
To execute a command procedure that contains qualifiers or parameters, or both, for a specific command line, place the @ command where the qualifiers or parameters normally would be in the command line. Then specify the name of the command procedure file containing the qualifiers or parameters.
If the command procedure file begins with parameters for the command, the @ command must be preceded by a space. For example:
$ CREATE TEST.COM TIME [Ctrl/Z] $ SHOW @TEST 14-SEP-2001 17:20:26
If the file begins with qualifiers for the command, do not precede the @ command with a space. For example:
$ CREATE TEST_2.COM /SIZE [Ctrl/Z] $ DIR@TEST_2 Directory WORK$:[SCHEDULE] JANUARY.TXT;8 14-DEC-2001 15:47:45.57 FEBRUARY.TXT;7 14-DEC-2001 15:43:16.20 MARCH.TXT;6 14-DEC-2001 11:11:45.74 . . . Total of 11 files.
If the file contains parameters or qualifiers, or both, do not begin the lines in the file with dollar signs. Any additional data on the command line following @filespec is treated as parameters for the procedure.

Qualifier

/OUTPUT=filespec
Specifies the name of the file to which the command procedure output is written. By default, the output is written to the current SYS$OUTPUT device. The default output file type is .LIS. The asterisk (*) and the percent sign (%) wildcard characters are not allowed in the output file specification. System responses and error messages are written to SYS$COMMAND as well as to the specified file. The /OUTPUT qualifier must immediately follow the file specification of the command procedure; otherwise, the qualifier is interpreted as a parameter to pass to the command procedure.
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 will be restored to its original equivalence string. This produces the same result as using the /OUTPUT qualifier when you execute the command procedure.

Examples

#1
$ CREATE DOFOR.COM $ ON WARNING THEN EXIT $ IF P1.EQS."" THEN INQUIRE P1 FILE $ FORTRAN/LIST 'P1' $ LINK 'P1' $ RUN 'P1' $ PRINT 'P1' `[Ctrl/Z]` $ @DOFOR AVERAGE

This example shows a command procedure, named DOFOR.COM, that executes the FORTRAN, LINK, and RUN commands to compile, link, and execute a program. The ON command requests that the procedure not continue if any of the commands result in warnings or errors.
When you execute DOFOR.COM, you can pass the file specification of the FORTRAN program as the parameter P1. If you do not specify a value for P1 when you execute the procedure, the INQUIRE command issues a prompting message to the terminal and equates what you enter with the symbol P1. In this example, the file name AVERAGE is assigned to P1. The file type is not included because the commands FORTRAN, LINK, RUN, and PRINT provide default file types.

#2
$ @MASTER/OUTPUT=MASTER.LOG

This command executes a procedure named MASTER.COM; all output is written to the file MASTER.LOG.

#3
$ CREATE FILES.COM .FOR, .OBJ `[Ctrl/Z]` $ DIRECTORY @FILES

This example shows a command procedure, FILES.COM, that contains parameters for a DCL command line. The entire file is treated by DCL as command input. You can execute this procedure after the DIRECTORY command to get a listing of all FORTRAN source and object files in your current default directory.

#4
$ CREATE QUALIFIERS.COM /DEBUG/SYMBOL_TABLE/MAP/FULL/CROSS_REFERENCE `[Ctrl/Z]` $ LINK SYNAPSE@QUALIFIERS

This example shows a command procedure, QUALIFIERS.COM, that contains qualifiers for the LINK command. When you enter the LINK command, specify the command procedure immediately after the file specification of the file you are linking. Do not type a space between the file specification and the @ command.

#5
$ CREATE SUBPROCES.COM $ RUN 'P1' - /BUFFER_LIMIT=1024 - /FILE_LIMIT=4 - /PAGE_FILES=256 - /QUEUE_LIMIT=2 - /SUBPROCESS_LIMIT=2 - 'P2' 'P3' 'P4' 'P5' 'P6' 'P7' 'P8' `[Ctrl/Z]` $ @SUBPROCES LIBRA /PROCESS_NAME=LIBRA

$ CREATE SUBPROCES.COM
$ RUN 'P1' -
  /BUFFER_LIMIT=1024 - 
  /FILE_LIMIT=4 -
  /PAGE_FILES=256 -
  /QUEUE_LIMIT=2 -
  /SUBPROCESS_LIMIT=2 -
  'P2'  'P3'  'P4'  'P5'  'P6'  'P7'  'P8'
[Ctrl/Z]
$ @SUBPROCES  LIBRA  /PROCESS_NAME=LIBRA

This example shows a command procedure named SUBPROCES.COM. This procedure issues the RUN command to create a subprocess to execute an image and also contains qualifiers defining quotas for subprocess creation. The name of the image to be run is passed as the parameter P1. Parameters P2 to P8 can be used to specify additional qualifiers.
In this example, the file name LIBRA is equated to P1; it is the name of an image to execute in the subprocess. The qualifier /PROCESS_NAME=LIBRA is equated to P2; it is an additional qualifier for the RUN command.

#6
$ CREATE EDOC.COM $ ASSIGN SYS$COMMAND: SYS$INPUT $ NEXT: $ INQUIRE NAME "File name" $ IF NAME.EQS."" THEN EXIT $ EDIT/TPU 'NAME'.DOC $ GOTO NEXT `[Ctrl/Z]` $ @EDOC

This procedure, named EDOC.COM, invokes the EVE editor. When an edit session is terminated, the procedure loops to the label NEXT. Each time through the loop, the procedure requests another file name for the editor and supplies the default file type .DOC. When a null line is entered in response to the INQUIRE command, the procedure terminates with the EXIT command.
The ASSIGN command changes the equivalence name of SYS$INPUT for the duration of the procedure. This change allows the EVE editor to read input data from the terminal, rather than from the command procedure file (the default input data stream if SYS$INPUT had not been changed). When the command procedure exits, SYS$INPUT is reassigned to its original value.

#7
! PEOPLE.DAT ! A set of data with embedded key qualifiers for the SORT command. ! ! Usage: SORT@PEOPLE.DAT ! /KEY=(POS:10,SIZE:10) sys$input people.out Fred Flintstone 555-1234 Barney Rubble 555-2244 Wilma Flintstone 555-1234 Betty Rubble 555-2244 George Slate 555-8911 Dino Dinosaur 555-1234 $! $ purge people.out $ type people.out

! PEOPLE.DAT
! A set of data with embedded key qualifiers for the SORT command.
!
! Usage: SORT@PEOPLE.DAT
!
/KEY=(POS:10,SIZE:10) sys$input people.out
Fred     Flintstone    555-1234
Barney   Rubble        555-2244
Wilma    Flintstone    555-1234
Betty    Rubble        555-2244
George   Slate         555-8911
Dino     Dinosaur      555-1234
$!
$ purge people.out
$ type people.out

Creates a sorted list of people in file PEOPLE.OUT and displays it. This demonstrates when using "@" in the middle of a DCL command, DCL redirects the entire file as command input.

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