Consider this example datafile:

Na      0.0     1.0     0.0
Cl      1.0     0.0     0.0
Na      0.0    -1.0     0.0

Since the data items (element type and coordinates) are separated by whitespace, we need only provide the target variables to the relevant command - a formatting string, as is demanded by the printf command, is not required. Using the readline command, the following code will parse this data correctly:

double x,y,z;
string el;
while (!eof()) { readline(el,x,y,z); newatom(el,x,y,z); }

The variables el, x, y, and z will, at any one time, contain the element type and coordinates from one line of the file. In an analogous manner, the data may be written out again with the corresponding writeline command:

for (atom i = aten.model.atoms; i; ++i) writeline(i.symbol,i,rx,i.ry,i.rz);

Each line will have the individual data items separated by a single space.

The readnext command reads in a single delimited item from a source file, preserving the remainder of the input line for subsequent operations. If there is no data left on the current line, a new line is read and the first delimited item is returned. The example above might be written in a slightly clunkier form as:

double x,y,z;
string el;
while (!eof())
{
	readnext(el);
	readnext(x);
	readnext(y);
	readnext(z);
	newatom(el,x,y,z);
}

For all delimited reading operations, items of data read from the line are converted automatically into the type of the destination variable. So, the atom coordinates read in above, which are put into 'double'-type variables, could equally well be put into string variables. Standard C routines are used to convert data items in this way, and only some conversions make sense. For instance, attempting to read an item which is a proper character string (such as element symbol/name data) into a double or integer variable does not make sense. No error message will be raised, and the variables will likely be set to a value of zero (or whatever passes for 'zero' in the context of the type).

For all delimited writing operations, a suitable standard format specifier is chosen with which to write out the data.