File IO C++ Reference

Load, save, and append text files from C++ with UFileIO.

Header: FileIO.h · Class: UFileIO

Each function takes an EFileLocation that picks the base directory, and a file name relative to it. For more on how the files are written, see the File IO nodes.

Name	Description
LoadFileToString	Reads a text file into an FString.
SaveTextToFile	Writes text to a file, replacing any existing contents.
AppendTextToFile	Adds text to the end of a file, creating it if needed.
EFileLocation	The base directory for the file.

EFileLocation

enum class EFileLocation : uint8 { ProjectSaved, UserDocuments, ProjectContent };

Value	Base directory
EFileLocation::ProjectSaved	FPaths::ProjectSavedDir(), your project's Saved folder.
EFileLocation::UserDocuments	FPlatformProcess::UserDir(), the user's Documents folder. On Android, this is /storage/emulated/0/Documents/.
EFileLocation::ProjectContent	FPaths::ProjectContentDir(), your project's Content folder.

The full path is the base directory combined with the file name using FPaths::Combine, so the file name can include subfolders, like Logs/DebugDump.txt.

LoadFileToString

static bool UFileIO::LoadFileToString(EFileLocation LoadLocation, FString FileName, FString& OutString, FString& OutFilePath);

Reads a text file and returns its contents.

Name	Description
LoadLocation	The base directory to load from.
FileName	The file to read, including its extension. Taken by value.
OutString	Receives the contents of the file.
OutFilePath	Receives the full path the function tried to read, whether or not it succeeded.

Returns: true if the file was read successfully.

#include "FileIO.h"

FString Contents;
FString FilePath;
if (UFileIO::LoadFileToString(EFileLocation::ProjectSaved, TEXT("Config/Settings.txt"), Contents, FilePath))
{
    // Use Contents
}

SaveTextToFile

static bool UFileIO::SaveTextToFile(EFileLocation SaveLocation, const FString& FileName, const FString& Content, FString& OutFullPath);

Writes text to a file, replacing any existing contents.

Name	Description
SaveLocation	The base directory to save to.
FileName	The file to write, including its extension.
Content	The text to write.
OutFullPath	Receives the full path the file was written to.

Returns: true if the file was saved successfully.

FString SavedPath;
UFileIO::SaveTextToFile(EFileLocation::ProjectSaved, TEXT("Logs/DebugDump.txt"), DumpText, SavedPath);

SavedPath receives the full path, and the Output Log shows:

LogTemp: Successfully saved file to: D:/MyGame/Saved/Logs/DebugDump.txt

WARNING

SaveTextToFile overwrites existing files without asking. Use AppendTextToFile to keep existing content.

AppendTextToFile

static bool UFileIO::AppendTextToFile(EFileLocation SaveLocation, const FString& FileName, const FString& Content, FString& OutFullPath, const bool bAddLineBreak = true);

Adds text to the end of a file, creating the file if it doesn't exist.

Name	Description
SaveLocation	The base directory to save to.
FileName	The file to append to, including its extension.
Content	The text to append.
OutFullPath	Receives the full path the file was written to.
bAddLineBreak	When true (the default), adds a line feed (\n) after Content.

Returns: true if the text was written successfully.

FString EventsPath;
UFileIO::AppendTextToFile(EFileLocation::ProjectSaved, TEXT("Logs/Events.txt"), TEXT("Level loaded"), EventsPath);

NOTE

Every UFileIO function writes a success or failure message, including the full path, to the Output Log under LogTemp.