System Debug Reference Manual > Chapter 2 User Interface

Variables

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System Debug provides variables in which values may be stored for use as operands in expressions. Variable names must begin with an alphabetic character, which may be followed by any combination of alphanumeric, apostrophe ('), underscore (_), or dollar sign ($) characters. Variable names are case insensitive and may not exceed 32 characters.

System Debug supports two levels of variable scoping: global and local. Global variables are defined by the VAR command and exist for the lifetime of the System Debug session (unless removed by the VARD command):


  $nmdebug > var v1 $2f
  $nmdebug > var s2 = "hello mom"
  $nmdebug > var p3:lptr = 2f.102c

The type of a variable is determined by the type of the expression which computes its value. The optional :type syntax which follows the variable name imposes a check on the expression type for that particular assignment only. It does not establish the variable's type over its entire lifetime. A value of a different type may be assigned to the same variable by a subsequent VAR command.

Local variables are defined by the LOC command only from within macro bodies and exist only for the lifetime of the macro in which they are defined. Local variable definitions nest with macro execution level, and they supercede global variables of the same name. Note that local variables normally are not visible from outside the macro in which they are created (that is, from macros called by the one in which they are created). To make local variable visible to called macros, the environment variable NONLOCALVARS must be TRUE.


   loc v1 200
   loc s2 = "new string"

Note that, although a macro cannot reference the value of a global variable once a local variable of the same name has been defined, it may change the global value by using the VAR command instead of LOC.

!variable

The use of the letters a through f to denote hex digits implies the possibility of ambiguity between hex constants and variable names composed of just these characters. System Debug warns the user of this occurrence when such variables are defined by the VAR and LOC commands, but uses the value of the constant when the name occurs in an expression. This may be overridden by preceding the variable name with the exclamation point as follows:


   $nmdebug > var a 123
   Variable name collides with hex numeric literal.  (warning #55)
     Name: "a"
   $nmdebug > wl a+1     /* a is a hex constant here
   $b
   $nmdebug > wl !a+1    /* !a references the variable a
   $124
   $nmdebug >

Operator Precedence

Environment Variables

Variables

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