legacy/src/main/java/ucar/nc2/NetcdfFileWriteable.java
public void updateAttribute(ucar.nc2.Variable v2, Attribute att) throws IOException {
    if (defineMode)
      throw new UnsupportedOperationException("in define mode");
    spiw.updateAttribute(v2, att);
  }
public void updateAttribute(ucar.nc2.Variable v2, Attribute att) throws IOException {
    if (defineMode)
      throw new UnsupportedOperationException("in define mode");
    spiw.updateAttribute(v2, att);
  }
public void updateAttribute ( ucar . nc2 . Variable v2 , Attribute att ) throws IOException { if ( defineMode ) throw new UnsupportedOperationException ( "in define mode" ) ; spiw . updateAttribute ( v2 , att ) ; }
Update the value of an existing attribute. Attribute is found by name, which must match exactly.
You cannot make an attribute longer, or change the number of values.
For strings: truncate if longer, zero fill if shorter.  Strings are padded to 4 byte boundaries, ok to use padding if it exists.
For numerics: must have same number of values.

@param v2  variable, or null for global attribute
@param att replace with this value
@throws IOException if I/O error
Update the value of an existing attribute . Attribute is found by name which must match exactly . You cannot make an attribute longer or change the number of values . For strings : truncate if longer zero fill if shorter . Strings are padded to 4 byte boundaries ok to use padding if it exists . For numerics : must have same number of values .