Reading lines from a data file

Question

Problem: Reading data file with multiple entries on a single line

• The easiest way I have found to do this is to read the whole line as string and then use internal reads to extract the non-blank values.

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Problems with that solution:

• Requires you to know the maximum length of any given line in the data file which is often not possible. or
• Requires you to create an arbitrary and excessively long string variable which wastes memory.

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Is there any other way of doing this?

Answer 1

Using deferred length character and non-advancing reads avoids the problems you mention in your question.

Continuing to parse of the resulting line using internal IO with explicit formats then avoids the potential for user "surprise" associated with the more obscure features of list directed formatting and allows far more scope and control over input error detection and reporting.

Answer 2

You can directly read multiple items from a one or multiple lines. For example:

read (5, *) a, b, c, d

will read four values from one to many lines.