FileOpen / FileWrite Bug?

[oasis375]

This doesn't work, it deletes (overwrites) file contents:

$hFile = FileOpen("file.txt", 2)
$content1 = FileRead($hFile)
$content2 = StringReplace($content1, "old", "new")
FileWrite($hFile, $content2)
FileClose($hFile)

Why? Instead, I have to use this workaround:

$hFile = FileOpen("file.txt")
$content1 = FileRead($hFile)
$content2 = StringReplace($content1, "old", "new")
FileClose($hFile)
$hFile = FileOpen("file.txt",2)
FileWrite($hFile, $content2)
FileClose($hFile)

That's it, opening, closing and reopening the file.

Function reference says: FileWrite. "Write text/data to the end of a previously opened file." (Does it mean "append"?).

Remarks: "The file must be opened in write mode or the FileWrite() command will fail."

But what write mode? $FO_APPEND (1) = Write mode (append to end of file). $FO_OVERWRITE (2) = Write mode (erase previous contents).

 

[jchd]

In the general case, changing part of a file implies reading it, performing the change then rewriting it in full.

Yet you can somehow streamline the code:

$changed = StringReplace(FileRead("file.txt"), "old", "new")
$hFile = FileOpen("file.txt", 2)
FileWrite($hFile, $changed)
FileClose($hFile)

 

[oasis375]

OK, finally I discovered that AutoIt doesn't have a read&write mode, like other programming languages, but there's a workaround using FileSetPos() before each Read/Write operation.

$hFile = FileOpen("file.txt", 1)
FileSetPos($hFile, 0, 0)
$content1 = FileRead($hFile)
$content2 = StringReplace($content1, "old", "new")
FileSetPos($hFile, 0, 0)
FileWrite($hFile, $content2)
FileClose($hFile)

Reference:

FileOpen("filename", $FO_OVERWRITE) deletes file contents, at the same moment.

[Bowmore]

The simplest way, in AutoIt, to do what you are doing is this

#include <FileConstants.au3>

$content1 = FileRead("file.txt")
$hFile = FileOpen("file.txt", $FO_OVERWRITE)
$content2 = StringReplace($content1, "old", "new")
FileWrite($hFile, $content2)
FileClose($hFile)

 

[jchd]

Isn't that what I posted above?

[Bowmore]

1 minute ago, jchd said:

Isn't that what I posted above?

Yes it is but oasis375 didn't appear to understood your your first compounded line, so I set it out one statement per line to make it clearer.

[oasis375]

8 hours ago, jchd said:

Isn't that what I posted above?

Sorry if I upset you. What I didn't understand was that AutoIt doesn't have a method to read and write at the same time, and that $FO_OVERWRITE deletes file contents, at the same moment. So mine was a conceptual problem, not a coding one.

Anyway, thank you guys for your replies.