Opens a file to read specific content from it and/or to write new content into it.

FileObj := FileOpen(Filename, Flags , Encoding)



Type: String

The path of the file to open, which is assumed to be in A_WorkingDir if an absolute path isn't specified.

Specify an asterisk (or two) as shown below to open the standard input/output/error stream:

FileOpen("*", "r")   ; for stdin
FileOpen("*", "w")   ; for stdout
FileOpen("**", "w")  ; for stderr

Type: String or Integer

Either a string of characters indicating the desired access mode followed by other options (with optional spaces or tabs in between); or a combination (sum) of numeric flags. Supported values are described in the tables below.


Type: String or Integer

The code page to use for text I/O if the file does not contain a UTF-8 or UTF-16 byte order mark, or if the h (handle) flag is used. If omitted, the current value of A_FileEncoding is used.

See FileEncoding for a list of possible values.


Access modes (mutually-exclusive)

Flag Dec Hex Description
r 0 0x0 Read: Fails if the file doesn't exist.
w 1 0x1 Write: Creates a new file, overwriting any existing file.
a 2 0x2 Append: Creates a new file if the file didn't exist, otherwise moves the file pointer to the end of the file.
rw 3 0x3 Read/Write: Creates a new file if the file didn't exist.
h     Indicates that Filename is a file handle to wrap in an object. Sharing mode flags are ignored and the file or stream represented by the handle is not checked for a byte order mark. The file handle is not closed automatically when the file object is destroyed and calling Close has no effect. Note that Seek, Pos and Length should not be used if Filename is a handle to a nonseeking device such as a pipe or a communications device.

Sharing mode flags

Flag Dec Hex Description
-rwd     Locks the file for read, write and/or delete access. Any combination of r, w and d may be used. Specifying - is the same as specifying -rwd. If omitted entirely, the default is to share all access.
  0 0x0 If Flags is numeric, the absence of sharing mode flags causes the file to be locked.
  256 0x100 Shares read access.
  512 0x200 Shares write access.
  1024 0x400 Shares delete access.

End of line (EOL) options

Flag Dec Hex Description
`n 4 0x4 Replace `r`n with `n when reading and `n with `r`n when writing.
`r 8 0x8 Replace standalone `r with `n when reading.

Return Value

Type: File

The return value is a new File object encapsulating the open handle to the file. Use the methods and properties of this object to access the file's contents.


If the file cannot be opened, an OSError is thrown.


File.ReadLine always supports `n, `r`n and `r as line endings and does not include them in its return value, regardless of whether the `r or `n options are used. The options only affect translation of line endings within the text returned by File.Read or written by File.Write or File.WriteLine.

When a UTF-8 or UTF-16 file is created, a byte order mark is written to the file unless Encoding (or A_FileEncoding if Encoding is omitted) contains UTF-8-RAW or UTF-16-RAW.

When a file containing a UTF-8 or UTF-16 byte order mark (BOM) is opened with read access, the BOM is excluded from the output by positioning the file pointer after it. Therefore, File.Pos may report 3 or 2 immediately after opening the file.

FileEncoding, File Object, FileRead


Writes some text to a file then reads it back into memory (it provides the same functionality as this DllCall example).

FileName := FileSelect("S16",, "Create a new file:")
if (FileName = "")
    FileObj := FileOpen(FileName, "w")
catch as Err
    MsgBox "Can't open '" FileName "' for writing."
        . "`n`n" Type(Err) ": " Err.Message
TestString := "This is a test string.`r`n"  ; When writing a file this way, use `r`n rather than `n to start a new line.

; Now that the file was written, read its contents back into memory.
    FileObj := FileOpen(FileName, "r-d") ; read the file ("r"), share all access except for delete ("-d")
catch as Err
    MsgBox "Can't open '" FileName "' for reading."
        . "`n`n" Type(Err) ": " Err.Message
CharsToRead := StrLen(TestString)
TestString := FileObj.Read(CharsToRead)
MsgBox "The following string was read from the file: " TestString

Opens the script in read-only mode and read its first line.

Script := FileOpen(A_ScriptFullPath, "r")
MsgBox Script.ReadLine()

Demonstrates the usage of the standard input/output streams.

; Open a console window for this demonstration:
; Open the application's stdin/stdout streams.
stdin  := FileOpen("*", "r")
stdout := FileOpen("*", "w")
stdout.Write("Enter your query.`n\> ")
stdout.Read(0) ; Flush the write buffer.
query := RTrim(stdin.ReadLine(), "`n")
stdout.WriteLine("Your query was '" query "'. Have a nice day.")
stdout.Read(0) ; Flush the write buffer.
Sleep 5000