Simple Fortran Question: Incrementing a FILE name within a loop

[Michael_Cupples]

I am looping on IHIST in the open statement below. I want to change the file name 'test100.txt' on the during looping such that I get a set of files at the end such as test101.txt, test102.txt, ..., test1000.txt

Pointing me to a known solution would be much appreciated. Note, I am new to character manipulation in FORTRAN, so do not understand how to formulate this problem

OPEN (UNIT=100+IHIST, FILE='test100.txt', STATUS='UNKNOWN')

Mike

[DavidWhite · Accepted solution]

WRITE(filename,'(a,i4.4,a)') "TEST",i,".TXT"

will enable you to create filenames from TEST0000.TXT to TEST9999.TXT

I'm not sure if you can specify UNIT=100+IHIST - hopefully someone else will answer that for you.

David

[mecej4]

For the syntax of the OPEN statement, see section 9.4 of the Standard. You can see there that the unit number is allowed to be specified as a scalar integer expression.

If you must have files named test100.txt,... rather than test0100.txt, ...:

[fortran]character*12 :: filename
integer :: iunit

if(iunit.LT. 1000)then
   write(filename,'("TEST",I3,".TXT")')iunit
   open(unit=iunit+100,file=filename,status='unknown')
   ...
   close(unit=iunit)
else
   write(filename,'("TEST",I4,".TXT")')iunit
   open(unit=iunit+100,file=filename,status='unknown')
   ...
   close(unit=iunit)
endif   [/fortran]

[Les_Neilson]

Or just use the format I0 (that is zero)

Les