Fortran 90 how to write very long output lines of different length

Question

I\'ve spent hours scouring the internet for a solution to this problem and can\'t find anything. I have been trying to write unformatted output to a CSV output file with mul

Answer 1

This isn't a problem with the ACCESS used for the file (stream, sequential or direct) - it is a consequence of the format specification that you are using.

Note that you are not doing unformatted output. Formatted versus unformatted is a question of whether the output is intended to be human readable.

The star in the second specifier of the WRITE statement is a specification of list directed formatting. This means that the format used for the output is based on the list of things to be output. Beyond that and a small set of rules in the language for list directed output, you are pretty much leaving the appearance of things up to the Fortran processor (the compiler).

With list directed formatted output the processor is specifically allowed to insert as many records as it sees fit between items. It does that here, quite reasonably, in order to make it easier for people to read the file.

If you want more control over the appearance of your output, then use an explicit format. For example, something like:

write(unitout2,"(9999(G12.5,:,','))") bigArray

might be more appropriate.

(Technically when a sequential file is opened there is a processor defined maximum record length (in the absence of a programmer specified maximum length) that should not be exceeded. Practically, given the way sequential formatted files are stored on disk by nearly all current Fortran compilers, that technicality doesn't cause any problems.)