_FileWriteToLine Pitfall

[Funtime60]

I'm pretty sure this isn't the first time I've ran into this issue with _FileWriteToLine. I was trying to edit a large file in place without creating a temporary file. I tried to use _FileWriteToLine as I needed to replace a specific lines with a line of equal length. The issue I ran into is that _FileWriteToLine both reopens the file, then reads it entirely into an array, thus defeating the purpose I was using it for. (Which IIRC isn't mentioned in the help file). In fact I can think of few cases where it isn't just better to do what _FileWriteToLine is doing manually.

TL:DR if you want to REPLACE characters in a file without loading the entire file into memory, you'll need to use FileSetPos and FileWriteLine.

In case it wasn't clear, I'm writing this so that others and future me don't make the same mistake.

[Melba23]

Funtime60,

Quote

_FileWriteToLine both reopens the file, <...>. (Which IIRC isn't mentioned in the help file)

The Help file does mention that "A file may fail to open due to access rights or attributes"- which to me implies quite clearly that the function does open files when used.

And just how do you intend to modify a file without reading it into memory? Rewrite the values stored on the disk directly? Sounds like a quick route to disaster to me!

M23

[HurleyShanabarger]

3 hours ago, Funtime60 said:

TL:DR if you want to REPLACE characters in a file without loading the entire file into memory, you'll need to use FileSetPos and FileWriteLine.

Thank you for the tip, but I think overwriting would be the better term. Also you need to know the position for FileSetPos beforehand, as FileSetPos is reffering to the actual position in a file and not a line.

[Zedna]

To get posion of desired line in file you can read content of file by chunks in While loop and count number/position of each @CRLF in chunks.

After this While loop use FileOpen() + FileSetPos() + FileRead() + FileWrite() + FileClose() to overwrite only desired line in file.