Braces or Quotes or Brackets

Use Curly braces when the argument contains fixed information.  ACTION commands normally need only a single argument enclosed in curly braces.  Nesting an ACTION command inside another ACTION command requires the use of Square Brackets. Use Quotes to force the evaluation of a local variable. Brackets are also used to enclose expressions.

For the example,
SETVAL {rotatefan103=%ROTATEPLUS 12}
he tag name, the options don't change in the above example.

For the example,
SETVAL "position=%ROTATEPLUS $dx"

the speed of rotation changes as the variable dx changes.

For the example,
SETVAL tag1=[GETVAL tag2]

the value of tag1 is set equal to current value of tag2. Tags2 is read, then passed to SETVAL ACTION command for tag1.

For the example,

set deltat [expr $time2 - $time1]

the value of local variables time2 and time1 are evaluated as part of an expression.


For the example,
set x 1
set y 2

set z "$x + $y is [expr $x + $y]."

the value of local variable z is set to a text string that reads: 1 + 2 is 3.