# Problem after reading binary file with windows gfortran **URL:** \ **Category:** Compilers\ **Created:** [February 14, 2024, 1:17pm UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407 "2024-02-14T13:17:36Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![birdie](https://avatars.discourse-cdn.com/v4/letter/b/71e660/32.png) [@birdie](https://fortran-lang.discourse.group/u/birdie)\ **Post date:** [February 14, 2024, 1:17pm UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/1 "2024-02-14T13:17:36Z")
Hello, I face a very strange problem with my own (big) code when compiled with windows gfortran (no problem with old lahey compiler or linux gf): when I read information in a binary file, everything is ok during the process but, afterwards, the code is unable to read correctly real data from the keyboard or from text files, the figures after coma being systematically ignored. If I type 0.3, it understands 0., if I type 3.1416, it understands 3. and so on. From the keyboard, I can “overcome” the problem by typing 31416E-4 (nice!), etc, but no medicine from text file. Has anyone already experienced such curious behavior? Advices are welcome, thank-you. ---
**Author:** ![Arjen](https://avatars.discourse-cdn.com/v4/letter/a/b9bd4f/32.png) [@Arjen](https://fortran-lang.discourse.group/u/Arjen)\ **Post date:** [February 14, 2024, 1:41pm UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/2 "2024-02-14T13:41:26Z")
Welcome to the forum! Thje problem you sketch is something I have never encountered myself. It does not ring a single bell either. Can you experiment with taking out parts of the process of reading this binary file? Is there some point where the decimal point is recognised again? Could it be a setting in your program that changed the decimal separator from a point to a comma? An OPEN statement may contain the DECIMAL keyword to change the significance of a point and a comma, Just a few random thoughts. ---
**Author:** ![ParkerLewis](https://avatars.discourse-cdn.com/v4/letter/p/57b2e6/32.png) [@ParkerLewis](https://fortran-lang.discourse.group/u/ParkerLewis)\ **Post date:** [September 1, 2025, 3:41pm UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/3 "2025-09-01T15:41:57Z")
Hi, I have encountered the exact same behavior. W11, gcc 15.2 with mingw64 13.0.0 Reading and closing a formatted file is fine Reading and closing an unformatted file is fine After an unformatted file has been read (even for only one value) though, fractional parts of any future formatted reads are being dropped (eg : ‘31649.08’ will be read as ‘31649.00’) (If the unformatted file is only opened, but immediately closed without reading any value, then the problem does not appear) Adding DECIMAL=’POINT’ to the formatted OPEN statement and/or the READ statement does not solve the issue. Specifying the format (eg (F15.8)) in the READ statement does not solve the issue. If the content of the formatted file is written in exponential form, then there is no issue. Additionally, the issue only manifests itself when executing directly on Windows. If the exact same executable is launched by gdb (on Windows), then the issue is not present. Here is a minimum example to reproduce 🙂 > subroutine readtxt > t=0.0 > open(newunit=kf,file=“toto.txt”,form=‘FORMATTED’, > & status=‘OLD’,action=‘READ’,iostat=IPB) > print\*,‘IPB=’,IPB > if (IPB==0) then > read(kf,\*) t > print\*,‘t=’,t > endif > close(kf) > return > end > > subroutine readbin > OPEN(newunit=io,FILE=“toto.bin”,ACCESS=‘STREAM’, > & FORM=‘UNFORMATTED’,STATUS=‘OLD’,IOSTAT=IPB) > read(io) x > close(io) > return > end > > program toto > call readtxt > call readtxt > call readbin > call readtxt > call readtxt > return > end With `toto.txt` being a simple one line ASCII file with eg `123.456` written in it, and `toto.bin` any non-empty binary file. The end result produces the following output on Windows : `PS D:\Work\toto> .\a.exe` `IPB= 0 ` `t= 123.456001 ` `IPB= 0 ` `t= 123.456001 ` `IPB= 0 ` `t= 123.000000 ` `IPB= 0 ` `t= 123.000000` ---
**Author:** ![PierU](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/pieru/32/1848_2.png) [@PierU](https://fortran-lang.discourse.group/u/PierU)\ **Post date:** [September 1, 2025, 5:37pm UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/4 "2025-09-01T17:37:51Z")
I cannot reproduce the problem with gfortran 13;2 on Windows MSYS2 ---
**Author:** ![JohnCampbell](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@JohnCampbell](https://fortran-lang.discourse.group/u/JohnCampbell)\ **Post date:** [September 2, 2025, 4:32am UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/5 "2025-09-02T04:32:09Z")
I tidied up the code, but did not reproduce your error for the text file. I included routines to first write the files and a more consistent approach to using and reporting the iostat return from open. I think your problem may be with the files you are opening. Does your txt file have a end of line character as `` ? Why do you use RETURN in the main program ? ```auto subroutine readtxt t = 0.0 open ( newunit=kf, file='toto.txt', form='FORMATTED', & status='OLD', action='READ', iostat=IPB) if (IPB==0) read(kf,*) t print*,'readtxt : t=',t,' ipb=',ipb close(kf) return end subroutine readbin x = 0 OPEN (newunit=io, FILE='toto.bin', ACCESS='STREAM', & FORM='UNFORMATTED', STATUS='OLD', IOSTAT=IPB ) if (IPB==0) read(io) x print*,'readbin : x=',x,' ipb=',ipb close(io) return end program toto call writetxt call writebin do k = 1,3 call readtxt call readtxt call readbin call readtxt call readtxt end do return ! why this ? end subroutine writetxt t = 0 open ( newunit=kf, file='toto.txt', form='FORMATTED', & status='UNKNOWN', iostat=IPB) if (IPB==0) then t = 123.456 write(kf,*) t end if print*,'writetxt : t=',t,' ipb=',ipb close (kf) return end subroutine writetxt subroutine writebin x = 0 OPEN (newunit=io, FILE='toto.bin', ACCESS='STREAM', & FORM='UNFORMATTED', STATUS='unknown', IOSTAT=IPB ) if (IPB==0) then x = 234.567 write(io) x end if print*,'writebin : x=',x,' ipb=',ipb close (io) return end ``` ps : including text in posts on this forum is becoming a bit of an art ! ---
**Author:** ![ParkerLewis](https://avatars.discourse-cdn.com/v4/letter/p/57b2e6/32.png) [@ParkerLewis](https://fortran-lang.discourse.group/u/ParkerLewis)\ **Post date:** [September 2, 2025, 6:44am UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/6 "2025-09-02T06:44:44Z")
All right. I did some additional tests. At first, I came to think that there was as you suggested a link with the end of line characters, as it seemed I got different results depending on if the line in the .txt file ended with CR or CR+LF. But then I tried it again, and the issue is not systematic !!! Here are the results of 3 successive tests against the same .txt file (ending with CR LF) : ```auto PS D:\Work\toto> .\a.exe IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 PS D:\Work\toto> .\a.exe IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 IPB= 0 t= 123.000000 IPB= 0 t= 123.000000 PS D:\Work\toto> .\a.exe IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 IPB= 0 t= 123.456001 ``` For some reason, the 2nd test did reproduce the issue, but not the other ones… ! If I just manually spam the test, it will generate both kind of results, with no obvious pattern (?) Same behavior if the EOL is just LF. Both results will be generated by the test, with no apparent reason to determine which one each time. ---
**Author:** ![msz59](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@msz59](https://fortran-lang.discourse.group/u/msz59)\ **Post date:** [September 2, 2025, 9:35am UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/7 "2025-09-02T09:35:11Z")
> [@JohnCampbell](#): > > ps : including text in posts on this forum is becoming a bit of an art ! See [this topic](https://fortran-lang.discourse.group/t/new-post-editor-panel/9986) if your problem is the new, all-integrated editor panel. Once you get the old setup (two panels), you can embed your includes with standard three-backticks ``` syntax. ---
**Author:** ![ParkerLewis](https://avatars.discourse-cdn.com/v4/letter/p/57b2e6/32.png) [@ParkerLewis](https://fortran-lang.discourse.group/u/ParkerLewis)\ **Post date:** [September 2, 2025, 3:26pm UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/8 "2025-09-02T15:26:25Z")
I have made a bug report to GCC > **[121759 – Windows/MinGW: formatted reads lose decimal digits after binary...](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121759)** ---
**Author:** ![certik](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/certik/32/4_2.png) [@certik](https://fortran-lang.discourse.group/u/certik)\ **Post date:** [September 3, 2025, 5:31am UTC](https://fortran-lang.discourse.group/t/problem-after-reading-binary-file-with-windows-gfortran/7407/9 "2025-09-03T05:31:09Z")
Thanks for reporting it @ParkerLewis, that’s the way to go.