Purpose : Reads the eigvalues from file "eigval" 
           Usage   : rdeigval [-f -i -inter -I0 -ver -h -?].
 Options : 
 -f FILE : the data is read from file FILE
           rather than from ./eigval
           The string FILE may be a relative or full path-name.
 -i DIR : data is stored in directory DIR
 -inter : enables interactive plotting
 -I0    : set intesity of all lines to 1.0
 -u units : Define energy units for plot
 -ver    : Version information about the program 
 -h      : Print this help text. 
 -?      : Print this help text.