NAME

       incr - Increment the value of a variable

SYNOPSIS

       incr varName ?increment?
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DESCRIPTION

       Increments  the  value  stored  in  the  variable whose name is varName.  The value of the
       variable must be an integer.  If increment is supplied then its value (which  must  be  an
       integer) is added to the value of variable varName;  otherwise 1 is added to varName.  The
       new value is stored as a decimal string in variable varName and also returned as result.

       Starting with the Tcl 8.5 release, the variable varName passed to incr may be  unset,  and │
       in  that  case, it will be set to the value increment or to the default increment value of │
       1.

EXAMPLES

       Add one to the contents of the variable x:
              incr x

       Add 42 to the contents of the variable x:
              incr x 42

       Add the contents of the variable y to the contents of the variable x:
              incr x $y

       Add nothing at all to the variable x (often useful for checking whether an argument  to  a
       procedure is actually integral and generating an error if it is not):
              incr x 0

SEE ALSO

       expr(3tcl)

KEYWORDS

       add, increment, variable, value