n OpenVMS, lexicals are special functions built into the DCL (Digital Command Language) that provide information about various aspects of the system and manipulate data. Here's a breakdown of what they are and what they do:
What are Lexical Functions?
Lexical functions are evaluated by the DCL interpreter during the initial processing of a command line.
They return values that can be used within the command itself.
This allows for more dynamic and flexible commands compared to just using static values.
What kind of information can they provide?
Lexical functions offer a variety of information about:
Your process: Details like process ID, name, and attributes.
The system: Information about the current date, time, system version, and cluster membership.
Files and devices: Get details like file size, creation date, and device characteristics.
Logical names: Look up the definition of logical names defined for your user account.
Strings and data types: Functions to manipulate strings, convert between data types, and perform basic arithmetic operations.
Benefits of using Lexical Functions?
Dynamic commands: Lets you build commands that adapt based on the current system state or user environment.
Improved readability: Code can be more concise and easier to understand by using lexicals instead of complex command sequences.
Error handling: Certain lexicals can be used to check for conditions and handle errors within a command procedure.