how to read binary file generated by Fortran

Hi there,

I have a binary file created by Fortran as following:

open(199,file='arrival.bin',form='unformatted')
write(199) data

The data contains 20k lines of float data (such as 394.06663, 395.03748, ...).

I did some research that using fread could load the file. However I used the following lines, it's not working.

fid = fopen('arrival.bin','rb');
A = fread(fid,20000,'single');
fclose(fid);

Please help me. I appreciate that in advance.

[KSSV]

it's not working....why? Any error? What is the problem? Try:

A = fread(fid,20000,'float');

[JZ]

Thanks.

It should be 3xx.xxx, but output is:

A(1)
ans =
   1.1210e-44

That's not right.

[KSSV]

Attach your file.

[JZ]

hi KSSV, the file is attached. I appreciate your help.

Answer 1

[JZ]

Thanks. It's now 35301 Lines. The zip file is attached.

It should look like:

224.96563

229.13564

233.54383

238.08795

242.80805

247.71402

252.80785

258.09077

263.56534

271.67779

287.49825

303.33010

...

[JZ]

Any help please? :)

Answer 2

[James Tursa]

Unformatted Fortran is not the same as stream binary. Whereas stream binary is just the data itself, unformatted Fortran has extra bytes inserted in the file along with your data ... what is there is compiler dependent and you often have to poke around a bit to find out. You need to read and discard those extra bytes. E.g., to read the beginning of the file:

% File arrtimes.m
fid = fopen('arrtimes.bin','rb');
discard = fread(fid,[1 1],'*int32')
x = fread(fid,[10 1],'*double')
fclose(fid);

And a sample run with your file:

>> arrtimes
discard =
           8
x =
  224.9656
    0.0000
  229.1356
    0.0000
  233.5438
    0.0000
  238.0880
    0.0000
  242.8081
    0.0000

So, my code isn't quite matching up with your data since I am seeing double precision values not singles, and there are 0's in the result. Those 0's could easily be extra bytes written by Fortran and not your data, however. So maybe all you need to do is this:

fid = fopen('arrtimes.bin','rb');
discard = fread(fid,[1 1],'*int32'); % discard the beginning bytes
x = fread(fid,inf,'*double'); % read everything in
x = x(1:2:end); % discard those 0's
fclose(fid);

And after a run:

>> x(1:15)
ans =
  224.9656
  229.1356
  233.5438
  238.0880
  242.8081
  247.7140
  252.8079
  258.0908
  263.5653
  271.6778
  287.4983
  303.3301
  319.1987
  335.1084
  351.0560

[Walter Roberson]

Probably the most common for Unformatted Fortran binary is for there to be a 4 byte record length at the beginning and also the end of each record. Both sides was for historical reasons to permit tape drives to move backwards by record.

[JZ]

Thank you all for this. I really appreciate that.

Millions of thanks!