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Updated: 11 December 1998

OpenVMS User's Manual


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Chapter 14
14 Programming with DCL: Defining Symbols, Commands, and Expressions
     14.1     About Symbols
         14.1.1         Comparing Logical Names and Symbols
     14.2     Using Symbols
         14.2.1         Using Symbols to Represent DCL Commands
         14.2.2         Symbol Abbreviation
         14.2.3         Defining Foreign Commands
         14.2.4         Symbol Substitution
         14.2.5         Deleting Symbols
     14.3     Displaying Symbols
     14.4     Using Symbols with Other Symbols
         14.4.1         Symbol Concatenation
         14.4.2         Including Symbols in String Assignments
     14.5     Using Symbols to Store and Manipulate Data
     14.6     Character Strings
         14.6.1         Defining Character Strings
         14.6.2         Character String Expressions
         14.6.3         Character String Operations
         14.6.4         Comparing Character Strings
         14.6.5         Replacing Substrings
     14.7     Using Numeric Values and Expressions
         14.7.1         Specifying Numbers
         14.7.2         Internal Storage of Numbers
         14.7.3         Performing Arithmetic Operations
         14.7.4         Comparing Numbers
         14.7.5         Performing Numeric Overlays
     14.8     Using Logical Values and Expressions
         14.8.1         Logical Operations
         14.8.2         Logical Expressions
         14.8.3         Logical Operation Results
         14.8.4         Using Values Returned by Lexical Functions
         14.8.5         Order of Operations
         14.8.6         Evaluating Data Types
     14.9     Converting Value Types in Expressions
         14.9.1         Converting Strings to Integers
         14.9.2         Converting Integers to Strings
     14.10     Understanding Symbol Tables
         14.10.1         Local Symbol Tables
         14.10.2         Global Symbol Tables
         14.10.3         Symbol Table Search Order
     14.11     Masking the Value of Symbols
         14.11.1         SET SYMBOL Command
         14.11.2         Symbol Scoping State
     14.12     Understanding Symbol Substitution
         14.12.1         Forced Symbol Substitution
         14.12.2         Symbol Substitution Operators
     14.13     The Three Phases of Command Processing
         14.13.1         Phase 1: Command Input Scanning
         14.13.2         Phase 2: Command Parsing
         14.13.3         Phase 3: Expression Evaluation
         14.13.4         Repetitive and Iterative Substitution
         14.13.5         Undefined Symbols
     14.14     An Alternative to Using Symbols: Automatic Foreign Commands
         14.14.1         Using Automatic Foreign Commands
         14.14.2         Automatic Foreign Command Restrictions
Chapter 15
15 Programming with DCL: Introduction to Command Procedures
     15.1     Basic Information for Writing Command Procedures
         15.1.1         Default File Type
         15.1.2         Writing Commands
         15.1.3         Writing Command Lines
     15.2     Using Labels in Command Lines
         15.2.1         Labels in Local Symbol Tables
         15.2.2         Duplicate Labels
     15.3     Using Comments in Command Procedures
     15.4     How to Write Command Procedures
     15.5     Steps for Writing Command Procedures
         15.5.1         Step 1: Design the Command Procedure
         15.5.2         Step 2: Assign Variables and Test Conditionals
             15.5.2.1             Using the INQUIRE Command
             15.5.2.2             Preserving Literal Characters
             15.5.2.3             Testing Conditionals Using IF and THEN
             15.5.2.4             Writing Program Stubs
         15.5.3         Step 3: Add Loops
         15.5.4         Step 4: End the Command Procedure
             15.5.4.1             Using the EXIT Command
             15.5.4.2             Using the STOP Command
         15.5.5         Step 5: Test and Debug the Program Logic
             15.5.5.1             Debugging Command Procedures
             15.5.5.2             Enabling Verification During Execution
         15.5.6         Step 6: Add Cleanup Tasks
             15.5.6.1             Closing Files
             15.5.6.2             Deleting Temporary or Extraneous Files
             15.5.6.3             Commonly Changed Process Characteristics
             15.5.6.4             Ensuring Cleanup Operations Are Performed
         15.5.7         Step 7: Complete the Command Procedure
     15.6     Executing Command Procedures
         15.6.1         Executing Command Procedures from Within Other Command Procedures
         15.6.2         Executing Command Procedures on Remote Nodes
             15.6.2.1             Security Note
         15.6.3         Executing Command Procedures with DCL Qualifiers or Parameters
             15.6.3.1             Restrictions
         15.6.4         Executing Command Procedures Interactively
         15.6.5         Executing Command Procedures as Batch Jobs
             15.6.5.1             Remote Batch Jobs
             15.6.5.2             Restarting Batch Jobs
         15.6.6         Executing Command Procedures on Disk and Tape Volumes
             15.6.6.1             Executing on Private Disk Volumes
             15.6.6.2             Executing on Tape Volumes
     15.7     Exiting and Interrupting Command Procedures
         15.7.1         Methods of Exiting
         15.7.2         Exit-Handling Routines
     15.8     Handling Errors
         15.8.1         Default Error Actions
     15.9     Other Methods of Error Handling
         15.9.1         ON Command
     15.10     Using the SET NOON Command
     15.11     Handling Ctrl/Y Interruptions
         15.11.1         Stopping Command Procedures
         15.11.2         Stopping Privileged Images
     15.12     Setting Ctrl/Y Action Routines
         15.12.1         Using the ON Command
         15.12.2         Effects of Entering Ctrl/Y
     15.13     Disabling and Enabling Ctrl/Y Interruptions
         15.13.1         Using SET NOCONTROL=Y
         15.13.2         Using SET CONTROL=Y
     15.14     Detecting Errors in Command Procedures Using Condition Codes
         15.14.1         Displaying Condition Codes ($STATUS)
         15.14.2         Condition Codes with the EXIT Command
         15.14.3         Determining Severity Levels
         15.14.4         Testing for Successful Completion
     15.15     Using Commands That Do Not Set $STATUS
     15.16     Login Command Procedures
         15.16.1         Systemwide Login Command Procedures
         15.16.2         Personal Login Command Procedures
         15.16.3         Login Command Procedures in Captive Accounts


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