%N uvprobvr %F $MIR/src/subs/uvio.c
%D Return information about a variable.
%P rjs
%: uv-i/o
%B
FORTRAN call sequence:
        subroutine uvprobvr(tno,varname,type,length,update)
        integer tno,length
        character varname*(*),type*1
        logical update

  This checks whether a particular variable exists. If it does, this
  passes back the type and (current) length of the variable, and whether
  it was updated on the last call to uvread or uvscan.

  Input:
    tno         The handle of the input uv data file.
    varname     The name of the variable to check.
  Output:
    type        The type of the variable. If the variable does not
                exist, this is blank. Otherwise it is one of 'a', 'r',
                'i', 'd' or 'c'.
    length      The number of elements in the uv variable. If this is not
                known (which is true if the variable has never been read)
                then this will be zero.
    update      This will be set .true. if this variable was updated
                on the last call to uvread or uvscan.                   
