Fortran - Output File names

angura

Hi,

I looked around in some forums, but couldn't find a good answer to this problem: my programmes produce several output files. When the programm is finished, I add certain simulation parameters to the file name, so that I see later, to which simulation run this file belongs.
(for example, a file "result.dat" is renamed to "result_500.dat" because the 500 is a certain parameter in that programm).

Now i don't want to manually rename a lot of files, but instead I'm looking for a way to make Fortran incorporate certain variables in the file names.
I only know this way of declaration:
Assuming I have a certain variable (e.g. an integer called "number")
Is it possible to assign a file name "result_*number*.dat", so that I only have to change the value of "number" and all files have that in their names?

Thanks for your help.

Useful nucleus

A possible solution , say you have 10 files with differnet names and you want to add the number 19 to all of them . Put the initial names(i.e., before adding 19) of these files in a character array defined as follow:
CHARACTER(len=25),DIMENSION(10)::filenames

also, define a character that contains the number(19)
CHARACTER(len=2)::number
number='19' !The quotqtion are important

then to add the number to the names use the concatenation operator as follows:
DO i=1,10
filename(i)=filaename(i) // number// '.dat'
END DO

now you have the names ready in the array, you can open ten files now with the statement:
DO i=1,10
OPEN(UNIT=i+10,FILE=filename(i),STATUS='replace',ACTION='write')
END DO


Now you have ten files with the required names ready to write in them.


May be this is not the best way, but I hope it works for you.

angura

Thanks for your answer! That's exactly what I'm looking for.
I'm still having a little trouble though, because the numbers that should be in the filenames are integer values and I don't know how to convert them into characters.
It's supposed to work with the simple write - command, but somehow I can't get it to work correctly :(

Useful nucleus

Hi angura,

You can use an internal file to do this. Say we have an integer i=567, and a character called number and we want to assign the value of i to the character then this piece of code will do the job:
..........
INTEGER::i
CHARACTER(len=10)::number
i=567
WRITE(number,100) i
100 FORMAT(I3)
........


A couple of comments, check that the length of the character is enough since this can create a runtime error. Also note that the write statement above creates a buffer file and do the conversion .

mathmate

Take care that the number has three digits when you use format I3.
If you want numbers with a maximum of three digits, with leading zeroes for those below 100, you can use the Iw.m conversion, for example,
will produce 007 when i=7.
This is important because you do not want a file name like:
ACE 7.dat
but rather
ACE007.dat

melody33

I also have the same problem.

However, the answer doesn't work to me.
I used gfortran to compile, then it said filename must be scalar.
How can I fix this? or should I use another compiler?

angura

At which position does it complain, that filename should be scalar?
Could you post a minimal example of your code?

minger

I typically write to a variable, using variable and strings, which I then open. Here is an example from a subroutine I have:
In this particular routine, I open this file which I already have, and modify it, writing out a formatted or post processed file. I concactanate the filenames easily as:
I 'used' to open several files and then write or open the file unit number as the do loop iterator, i.e.
But the flexibility of the way I'm doing it up there will save you a lot of hassle down the road. I recommend it.