errno 79 (EFTYPE): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: a file whose type or format is unsuitable for the requested operation.

Could be also:
Constant	Type	OS
ELIBACC	errno	Linux
EOVERFLOW	errno	Solaris
NDIS_INTERNAL_ERROR	BugCheck Code	Windows

Previous	Next
ELIBACC	EOVERFLOW

EFTYPE

EFTYPE is a BSD/Darwin error for a file that exists but is not an acceptable type or format for the operation being attempted. It is broader than program loading: the XNU header lists it before the dedicated program-loading errors, so the failing API and the expected kind of object matter.

A filename suffix is not evidence of the file's actual identity. A Mach-O container can represent a relocatable object, an executable, a dynamic library, or a bundle; the Mach-O header records that distinction in its filetype field. A valid object of one kind can still be unsuitable where another kind is required.

Distinguish the nearby Darwin errors

EFTYPE is the general “wrong type or format” result.
EBADEXEC is a program-loading result for a bad executable image.
EBADMACHO identifies a structurally malformed Mach-O image.
EBADARCH means that the image has no CPU architecture usable by the loading process.

What to capture

Record the exact path and the API that rejected it; do not infer the object type from its extension.
Use file <path> to identify the container, then otool -hv <path> and otool -l <path> when it is expected to be Mach-O.
For a universal binary or plugin, inspect its slices with lipo -archs <path>; format and architecture are separate checks.
When the file came from an application bundle, compare it with the built or signed artifact before replacing anything. Renaming a file does not convert its Mach-O type.

References

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