Skip to content

ROM Writing Options

Overwriting files

By default, Igir will not overwrite or delete any files already in the output directory.

To change this behavior, the --overwrite option will force overwriting files in the output directory as necessary. Be careful with this option as it can cause unnecessary wear and tear on your hard drives.

The --overwrite-invalid option can also overwrite files in the output directory, but only if those files don't match the expected size and checksum. This uses the same logic as the igir test command. Combining this option with the igir clean command will result in your output directory being a perfect subset of files contained in your DATs.

Fixing ROM extensions

ROM dumpers don't always do a good job of using the generally accepted filename extension when writing files. In situations where DATs aren't provided, or information in DATs is incomplete, Igir has some ability to find the correct extension that filenames should have. This is done using file signatures, pieces of data that are common to every file of a certain format.

Here are some examples of common mistakes:

Incorrect extensions Correct extension
.fc Nintendo Family Computer
.nez Nintendo Entertainment System
.unh Nintendo Entertainment System (Unheadered)		 .nes Nintendo Entertainment System
.sgb Nintendo Super Game Boy .gb Nintendo Game Boy
.bin Sega Mega Drive / Genesis
.gen Sega Genesis		 .md Sega Mega Drive

This correction behavior can be controlled with the following option:

  • --fix-extension never

    Don't correct any ROM filename extensions. If a DAT doesn't provide a ROM filename, a default name of <game name>.rom will be used.

  • --fix-extension auto (default)

    When not using DATs (no --dat <path> option was provided), or when a DAT doesn't specify the filename for a ROM, then try to correct the filename extension.

  • --fix-extension always

    Always try to correct filename extensions, ignoring the information provided by DATs. You likely don't want this option.

See the igir --help message for the list of all known file types.