Standard output format using a variable

Question

In Fortran90 I would like to set the format of an output using a variable. My code looks like this:

fileUnit = 14
myFormat = '(10e18.10)' 
write (fileUnit,myFormat) myData

The value of myFormat can be any allowed for the type of myData. Is there a way to set myFormat such that the output is equivalent to coding

write (fileUnit,*) myData

You want a format equivalent to the *? There isn't any. But perhaps I don't understand your question. What does the sentence The value of myFormat can be any allowed for the type of myData. mean? — Vladimir F Героям слава
– Vladimir F Героям слава, Commented Oct 30, 2015 at 14:59
I'm sure you know but it should be myFormat = '(10e18.10)' — agentp
– agentp, Commented Oct 30, 2015 at 19:55
@VladimirF: Yes, I am basically looking for a format equivalent to the *. The sentence you highlighted just means that I'd like myData to be of any data type for which a standard output is defined. — Alessandro Leonardi
– Alessandro Leonardi, Commented Nov 2, 2015 at 13:55

casey · Accepted Answer · 2015-10-30 16:05:56Z

1

You cannot use a bare * in an explicit format specification like you can in a read or write statement. In the explicit format context, * represents an unlimited-format-item group that gives an infinite repeat count to a group of format-items rather than representing list directed formatting (see Cl. 9.6.2.2, R915, Fortran 2008).

The character variable holding your explicit format can be constructed at run-time, so your option to handle dynamic needs is to write code to determine the proper format specification based upon your data. Depending on your compiler, and if your data is a derived type, you may also have the option of defined output (See Cl. 9.6.4.8.3 Fortran 2008) to handle your needs.

answered Oct 30, 2015 at 16:05

casey

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agentp · Accepted Answer · 2015-10-30 20:00:10Z

1

If you want to programmatically switch between explicit and list directed format you could do something like this:

 if(myFormat.eq.'*')then
      write(unit,*)...
 else
      write(unit,myFormat)...
 end if

answered Oct 30, 2015 at 20:00

agentp

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