FileRead

Reads a file's contents into a variable.

FileRead, OutputVar, Filename

Parameters

OutputVar

The name of the variable in which to store the retrieved data. OutputVar will be made blank if a problem occurs such as the file being "in use" or not existing (in which case ErrorLevel is set to 1). It will also be made blank if Filename is an empty file (in which case ErrorLevel is set to 0).

Filename

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

Options: Zero or more of the following strings may be also be present immediately before the name of the file. Separate each option from the next with a single space or tab. For example: *t *m5000 C:\Log Files\200601.txt.

*c: Load a ClipboardAll file or other binary data. All other options are ignored when *c is present.

*m1024: If this option is omitted, the entire file is loaded unless there is insufficient memory, in which case an error message is shown and the thread exits (but Try can be used to avoid this). Otherwise, replace 1024 with a decimal or hexadecimal number of bytes. If the file is larger than this, only its leading part is loaded. Note: This might result in the last line ending in a naked carriage return (`r) rather than `r`n.

*t: Replaces any/all occurrences of carriage return & linefeed (`r`n) with linefeed (`n). However, this translation reduces performance and is usually not necessary. For example, text containing `r`n is already in the right format to be added to a Gui Edit control. Similarly, FileAppend detects the presence of `r`n when it opens a new file; it knows to write each `r`n as-is rather than translating it to `r`r`n. Finally, the following parsing loop will work correctly regardless of whether each line ends in `r`n or just `n: Loop, parse, MyFileContents, `n, `r.

*Pnnn: [AHK_L 42+]: Overrides the default encoding set by FileEncoding, where nnn must be a numeric code page identifier.

ErrorLevel

[v1.1.04+] This command is able to throw an exception on failure. For more information, see Runtime Errors.

ErrorLevel is set to 0 if the load was successful. It is set to 1 if a problem occurred such as: 1) file does not exist; 2) file is locked or inaccessible; 3) the system lacks sufficient memory to load the file.

A_LastError is set to the result of the operating system's GetLastError() function.

Reading Binary Data

Depending on the file, parameters and default settings, FileRead may interpret the file data as text and convert it to the native encoding used by the script. This is likely to cause problems if the file contains binary data, except in the following cases:

Note that once the data has been read into OutputVar, only the text before the first binary zero (if any are present) will be "seen" by most AutoHotkey commands and functions. However, the entire contents are still present and can be accessed by advanced methods such as NumGet().

Finally, FileOpen() and File.RawRead() or File.ReadNum() may be used to read binary data without first reading the entire file into memory.

Remarks

When the goal is to load all or a large part of a file into memory, FileRead performs much better than using a file-reading loop.

A file greater than 1 GB in size will cause ErrorLevel to be set to 1 and OutputVar to be made blank unless the *m option is present, in which case the leading part of the file is loaded.

FileRead does not obey #MaxMem. If there is concern about using too much memory, check the file size beforehand with FileGetSize.

FileOpen() provides more advanced functionality than FileRead, such as reading or writing data at a specific location in the file without reading the entire file into memory. See File Object for a list of functions.

Related

FileEncoding, FileOpen/File Object, file-reading loop, FileReadLine, FileGetSize, FileAppend, IniRead, Sort, UrlDownloadToFile

Examples

; Example #1: Read text file into OutputVar.
FileRead, OutputVar, C:\My Documents\My File.txt
; Example #2: Quickly sort the contents of a file.
FileRead, Contents, C:\Address List.txt
if not ErrorLevel  ; Successfully loaded.
{
    Sort, Contents
    FileDelete, C:\Address List (alphabetical).txt
    FileAppend, %Contents%, C:\Address List (alphabetical).txt
    Contents =  ; Free the memory.
}