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Zohar

How to Open a File for Both Read and Write?

14 posts in this topic

#1 ·  Posted (edited)

Hi

If I open a File like this:

Local $hFile =FileOpen($FilePath,0) ;0=Read
  $String_FileContent =FileRead($hFile)
FileClose($hFile)

Then I am able to successfully read the file.

If I open a File like this:

Local $hFile =FileOpen($FilePath,2) ;2=Write
  FileWrite($hFile,$String_FileContent)
FileClose($hFile)

Then I am able to successfully write to the file.

But what If I want to do both Read+Write in 1 FileOpen+Close?

How do I FileOpen() a file for both Read+Write?

When I try

Local $hFile =FileOpen($FilePath,2) ;2=Write
  $String_FileContent =FileRead($hFile)
FileClose($hFile)

Msg($String_FileContent)

The messagebox shows an empty string..

As If When FileOpen() with mode=2, then you can't Read from the file, only Write to it.

What should I do?

Edited by Zohar

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#2 ·  Posted (edited)

Mode 2 erases the previous contents of the file so there is nothing to read.

Edit: Use mode 1.

From the help...

1 = Write mode (append to end of file)

2 = Write mode (erase previous contents)

also from the help...

When reading and writing via the same file handle, the FileSetPos() function must be used to update the current file position.

Edit 2: Added link to FileSetPos()

Edited by JohnQSmith

Whenever someone says "pls" because it's shorter than "please", I say "no" because it's shorter than "yes".

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Hi

Regarding "1 = Write mode (append to end of file)",

The help file doesn't say it can be used for both Read+Write.

But I'll try it now, thank you.

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Zohar,

Mode 2 erases the current file contents (as explained in the Help file). However, Mode 1 will only append to the file (again as explained in the Help file). :)

So you may need to use 2 FileOpen/Close cycles depending on what you want to do with the content - a single call might not be possible. ;)

M23


Any of my own code posted anywhere on the forum is available for use by others without any restriction of any kind._______My UDFs:

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ArrayMultiColSort ---- Sort arrays on multiple columns
ChooseFileFolder ---- Single and multiple selections from specified path treeview listing
Date_Time_Convert -- Easily convert date/time formats, including the language used
ExtMsgBox --------- A highly customisable replacement for MsgBox
GUIExtender -------- Extend and retract multiple sections within a GUI
GUIFrame ---------- Subdivide GUIs into many adjustable frames
GUIListViewEx ------- Insert, delete, move, drag, sort, edit and colour ListView items
GUITreeViewEx ------ Check/clear parent and child checkboxes in a TreeView
Marquee ----------- Scrolling tickertape GUIs
NoFocusLines ------- Remove the dotted focus lines from buttons, sliders, radios and checkboxes
Notify ------------- Small notifications on the edge of the display
Scrollbars ----------Automatically sized scrollbars with a single command
StringSize ---------- Automatically size controls to fit text
Toast -------------- Small GUIs which pop out of the notification area

 

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#5 ·  Posted (edited)

JohnQSmith:

FileOpen() with mode=1 yielded the same result:

FileRead() returns an Empty String..

Melba23:

No way to do it in 1 FileOpen() at all? :/

Edited by Zohar

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#6 ·  Posted (edited)

Regarding "1 = Write mode (append to end of file)",

Don't forget the FileSetPos() otherwise the position pointer in the file will be at the end of the file on open (hence the "append") and there will be nothing to read.

Edit: So, if you wanted to read from the beginning of the file after opening it, you would need to add the following before your FileRead() command.

FileSetPos( $hFile, 0, 0 )
Edited by JohnQSmith

Whenever someone says "pls" because it's shorter than "please", I say "no" because it's shorter than "yes".

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JohnQSmith:

FileGetPos($hFile) returns 0, and not EOF..

But even If I do what you recommend:

FileSetPos($hFile,0,0)

I still get an empty string from FileRead()

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Did you open the file for reading?


If I posted any code, assume that code was written using the latest release version unless stated otherwise. Also, if it doesn't work on XP I can't help with that because I don't have access to XP, and I'm not going to.
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#9 ·  Posted (edited)

Umm... are you sure there's actually something in the file? If the file is empty, there is nothing to read.

Edit: I just tried it, and it works fine for me (using a file with text in it)...

$theFile = FileOpen("README.TXT", 1)
FileSetPos($theFile,0,0)
ConsoleWrite(FileRead($theFile))
FileClose($theFile)
Edited by JohnQSmith

Whenever someone says "pls" because it's shorter than "please", I say "no" because it's shorter than "yes".

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Zohar,

Try this: ;)

$hFile = FileOpen(@ScriptFullPath, 1)

FileSetPos($hFile, 0, 0)
$sText = FileRead($hFile)
MsgBox(0, "Content", $sText)

FileWrite($hFile, @CRLF & @CRLF & "New Stuff")

FileSetPos($hFile, 0, 0)
$sText = FileRead($hFile)
MsgBox(0, "Content", $sText)

FileClose($hFile)

Is that what you wanted? :)

M23


Any of my own code posted anywhere on the forum is available for use by others without any restriction of any kind._______My UDFs:

Spoiler

ArrayMultiColSort ---- Sort arrays on multiple columns
ChooseFileFolder ---- Single and multiple selections from specified path treeview listing
Date_Time_Convert -- Easily convert date/time formats, including the language used
ExtMsgBox --------- A highly customisable replacement for MsgBox
GUIExtender -------- Extend and retract multiple sections within a GUI
GUIFrame ---------- Subdivide GUIs into many adjustable frames
GUIListViewEx ------- Insert, delete, move, drag, sort, edit and colour ListView items
GUITreeViewEx ------ Check/clear parent and child checkboxes in a TreeView
Marquee ----------- Scrolling tickertape GUIs
NoFocusLines ------- Remove the dotted focus lines from buttons, sliders, radios and checkboxes
Notify ------------- Small notifications on the edge of the display
Scrollbars ----------Automatically sized scrollbars with a single command
StringSize ---------- Automatically size controls to fit text
Toast -------------- Small GUIs which pop out of the notification area

 

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#11 ·  Posted (edited)

Umm... are you sure there's actually something in the file? If the file is empty, there is nothing to read.

You are right!

The file's content was deleted by one of the earlier FileOpen(mode=2).

Once I fixed that, FileOpen(mode=1) works!!!

Thank you very much

Edited by Zohar

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#12 ·  Posted (edited)

BTW,

Did you notice that in the helpfile, in FileOpen(), mode=4 is missing?

What is mode=4? :)

Edited by Zohar

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I don't believe there is a mode 4.


If I posted any code, assume that code was written using the latest release version unless stated otherwise. Also, if it doesn't work on XP I can't help with that because I don't have access to XP, and I'm not going to.
Give a programmer the correct code and he can do his work for a day. Teach a programmer to debug and he can do his work for a lifetime - by Chirag Gude
How to ask questions the smart way!

I hereby grant any person the right to use any code I post, that I am the original author of, on the autoitscript.com forums, unless I've specifically stated otherwise in the code or the thread post. If you do use my code all I ask, as a courtesy, is to make note of where you got it from.

Back up and restore Windows user files _Array.au3 - Modified array functions that include support for 2D arrays.  -  ColorChooser - An add-on for SciTE that pops up a color dialog so you can select and paste a color code into a script.  -  Customizable Splashscreen GUI w/Progress Bar - Create a custom "splash screen" GUI with a progress bar and custom label.  -  _FileGetProperty - Retrieve the properties of a file  -  SciTE Toolbar - A toolbar demo for use with the SciTE editor  -  GUIRegisterMsg demo - Demo script to show how to use the Windows messages to interact with controls and your GUI.  -   Latin Square password generator

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#14 ·  Posted (edited)

Mode to open the file in.

Can be a combination of the following:

0 = Read mode (default)

1 = Write mode (append to end of file)

2 = Write mode (erase previous contents)

8 = Create directory structure if it doesn't exist (See Remarks).

16 = Force binary mode (See Remarks).

32 = Use Unicode UTF16 Little Endian reading and writing mode. Reading does not override existing BOM.

64 = Use Unicode UTF16 Big Endian reading and writing mode. Reading does not override existing BOM.

128 = Use Unicode UTF8 (with BOM) reading and writing mode. Reading does not override existing BOM.

256 = Use Unicode UTF8 (without BOM) reading and writing mode.

16384 = When opening for reading and no BOM is present, use full file UTF8 detection. If this is not used then only the initial part of the file is checked for UTF8.

The folder path must already exist (except using mode '8' - See Remarks).

Do you see anything in there that adds up to 4?

That having been said; the text I just quoted needs looking at.

Can be a combination of the following:

is technically incorrect. As far as I am aware you can not combine 0, 1, 2.

It should probably read something like

0, 1 or 2 can be combined with the following:

but that could be considered as nit picking.

EDIT:

BTW: You don't need to use FileOpen/FileClose at all for a simple FileRead() operation. Just FileRead() it to a variable, work on the variable and then write it back using FileOpen()/FileWrite()/FileClose() so you can set the write mode.

Edited by GEOSoft

George

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