Command syntax

command syntax

| GSI | Biophysics | Command subsystem |

Command syntax

The command syntax differs from the conventions used in the underlying operating systems. A command consists of a command name followed by a list of command parameters. General syntax:

   COMMAND   reqpos  ...   optpos  ...  /  KEYWORD(opt)  ...

Three different types of command parameters are possible.

Required positional parameters.
These parameters are always required by the system and cannot be defaulted. They are entered as values (numbers or character strings) immediately following the command name and are identified by the order in which they appear.
Optional positional parameters.
They are also identified by the order in which they appear but may be omitted causing default values to take effect. Individual parameters may be defaulted by the use of adjacent commas. The list as a whole may be truncated from the end (right to left).
Optional parameters.
Optional parameters are identified by a name (keyword) which may be followed by a value (number(s) or character string) enclosed in parantheses. Separated by the special character '/' from the list of positional parameters, they may be entered in any order. If omitted, default values take effect.
Optional parameters without an argument act as a switch which can assume the values 0 or 1, equivalent to false and true, respectively. Each optional parameter is provided with a default value. Two kinds of default values are possible:
- Static defaults.
  Their values are unchanged and take effect each time the corresponding parameters are not explicitly specified.
- Replaceable defaults.
  They act like static defaults, but their values are overwritten by the corresponding parameter values used last.

Items in a positional parameter list must be separated by blanks or commas.

Protecting delimiters

If a positional parameter value includes delimiters, i.e. blanks, commas or slashes (e.g. in filenames), it must be enclosed in single or double quotes.
Example:

   EXEC  "mydir/myfile"

Abbreviations

Most command and parameter names may be abbreviated as long as the remainder is unique.
Example:

                                                                             
   DISP A LIST / WINDOW(100,260)

is equivalent to

                                                                             
   D  A LIST / W(100,260)

Omitting optional positional parameters

A list of optional positional parameters can only be truncated from the end (right to left). However, an individual item may be omitted if a comma is typed instead. Example: Assume the command EXAMPLE is defined with three positional parameters. Then with:

                                                                             
   EXAMPLE  ,B C                                                               
   EXAMPLE  A,,C                                                               
   EXAMPLE  ,,C                                                                
   EXAMPLE  A

the 1st parameter, the 2nd parameter, the 1st and 2nd parameters, and the 2nd and 3rd parameters, respectively. are defaulted.

| GSI | Biophysics | Command subsystem |

Last updated: M.Kraemer@gsi.de, 2-Aug-1999

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