FileRead doesn't read from the start of the file per variable

[leuce]

Hello everyone

Is the result I'm getting, normal?  Here's my code:

$tbxfileopen = FileOpen ("IATE_export_29082018.tbx", 16) ; a 2 GB text file

$testfileopen0 = FileOpen ("test0.txt", 17)
$testfileopen1 = FileOpen ("test1.txt", 17)

$tbxfileread0 = FileRead ($tbxfileopen, 1000000)
$tbxfileread1 = FileRead ($tbxfileopen, 1000000)

FileWrite ($testfileopen0, $tbxfileread0)
FileWrite ($testfileopen1, $tbxfileread1)

I would have expected "test0.txt" and "test1.txt" to have the same content, but what I find is that "test1.txt" starts where "test0.txt" ends, despite the fact that the "FileRead" is being read into two separate variables.  Is this supposed to happen like that?  Why?  And, how can I avoid that... (except by using "FileOpen" twice).  I mean, surely FileRead always reads from the start of the file, so for each new FileRead instance, wouldn't it have to start from the start of the file again?

Thanks

Samuel

[Zedna]

Yes, it's OK.

Every FileRead() moves internal "current file position" for that opened file handle. 

Use FileSetPos() to move position to 0 before second FileRead() to achieve reading from the begin of file.

$tbxfileread0 = FileRead ($tbxfileopen, 1000000)
FileSetPos($tbxfileopen, 0, $FILE_BEGIN)
$tbxfileread1 = FileRead ($tbxfileopen, 1000000)

Look here

https://www.autoitscript.com/autoit3/docs/functions/FileSetPos.htm

 

Edited March 29, 2021 by Zedna

[leuce]

Thanks.

Edited March 29, 2021 by leuce

[JockoDundee]

2 hours ago, leuce said:

despite the fact that the "FileRead" is being read into two separate variables.

FileRead has no idea what variables, if even any, it’s return value may be going in to.  Therefore it can’t make decisions based on such.