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Porting TCL

TCL procedure PDFs must be portable as well. TCL is the TAE Command Language, used to write most VICAR procedures. Although it is designed to be fairly portable, in that the commands are the same for any version of TAE, there are some things you need to watch out for.

The most significant thing that will have to be changed is use of the dcl command inside a procedure. This command allows you to put VMS DCL commands in your procedure, which are, of course, not portable. The corresponding command under Unix is ush, which allows you to execute shell commands inside the procedure.

In order to use the dcl or ush commands, there has to be some way of determining which operating system you are on. Fortunately, there is a global variable called ``$syschar'' that holds the type of operating system. Index 1 in this variable is either ``UNIX'' or ``VAX_VMS''. For example:

procedure
parm file string
refgbl $syschar
body
if ($syschar(1) = "UNIX")
  ush rm &file
else
  dcl delete &file
end-if
end-proc

Unfortunately, there appears to be no straightforward way to determine the particular version of Unix, so stick to common shell commands.

Another major trouble area for porting TCL is filenames. Filenames and pathnames look much different under VMS and Unix. There is a lot of TCL code in VICAR that parses filenames, appends filenames to directories, etc. Many test scripts use hardcoded VMS directories and filenames to find test files. All of these will have to change. The same ``$syschar'' variable can be used to do different things with the filename, or pick different test files, based on which system you are using.

The ``$syschar'' variable may also be tested inside help files, help within a PDF, and menus via special conditional commands. These commands are part of TAE, but they are unfortunately not documented by TAE. The conditionals all test to see if the given string is in any element of the ``$syschar'' variable. Like other PDF/MDF directives, they should appear on a line by themselves with the ``.'' in the first column.

• .if string: Prints the following lines (up to .elseif or .ifend) if string is in ``$syschar''.

• .ifn string: Prints the following lines (up to .elseif or .ifend) if string is not in ``$syschar''.

• .elseif string: Prints the following lines of text (up to .ifend or another .elseif) if the previous condition was not met, and string is in ``$syschar''.

• .ifend: Ends a conditional clause.

• .if1 string: Single-line conditional. Just like .if, but only the next line is printed, and no .ifend is required.

• .ifn1 string: Single-line negative conditional. Just like .ifn, but only the next line is printed, and no .ifend is required.

For example, the following lines are taken from the TAE command mode help file (commode.hlp):

                CONT*INUE
.if VAX_VMS
                DCL              any-VMS/DCL-command
                DCL-NOINTERRUPT  any-VMS/DCL-command
.ifend
                DEFC*MD COMMAND=command-name STRING=replacement-string

...

                T*UTOR-NOSCREEN PROC=proc-subcmd  parameters
.if1 UNIX
                USH any-UNIX/shell-command
                WAIT-ASYNC JOB=job-name-list

...

                        RUNTYPE Command Qualifier (continued)

           If the command qualifier is set to BATCH, the following TAE
           message is displayed:

.if VAX_VMS
               Job (nnn) submitted to queue (que)

           where "nnn" is the assigned job number and "que" is
           the name of the queue the job was submitted to.

.elseif UNIX
                Batch job file "filename" submitted successfully.

           where "filename" is the batch job file name, defined
           as "proc".job.

.ifend

You should refer to the TAE documentation if you have more questions on writing portable TCL.