Retrieve file identification data
cc [flag...]
file... -lelf
[library]...
#include <libelf.h>
char *elf_getident(Elf * elf, size_t * ptr);
As the Introduction to elf subroutines explains, ELF provides a framework for various classes of files, where basic objects may have 32 bits, 64 bits, and so forth. To accommodate these differences, without forcing the larger sizes on smaller machines, the initial bytes in an ELF file hold identification information common to all file classes. Every ELF header e_ident has EI_NIDENT bytes with the following interpretation.
| e_ident Index | Value | Purpose |
|---|---|---|
| EI_MAG0 | ELFMAG0 | File identification |
| EI_MAG1 | ELFMAG1 | |
| EI_MAG2 | ELFMAG2 | |
| EI_MAG3 | ELFMAG3 | |
| EI_CLASS | ELFCLASSNONE | File class |
|
| ELFCLASS32 | |
|
| ELFCLASS64 | |
| EI_DATA | ELFDATANONE | Data encoding |
|
| ELFDATA2LSB | |
|
| ELFDATA2MSB | |
| EI_VERSION | EV_CURRENT | File version |
| EI_OSABI | ELFOSABI_NONE | Vendor extension identification |
| EI_OSABIVERSION | 0 | Vendor extension version |
| 9-15 | 0 | Unused, set to zero |
Other kinds of files [see the elf_kind subroutine] also may have identification data, though they would not conform to e_ident.
elf_getident returns a pointer to the file's initial bytes. If the library recognizes the file, a conversion from the file image to the memory image may occur. In any case, the identification bytes are guaranteed not to have been modified, though the size of the unmodified area depends on the file type. If ptr is non-null, the library stores the number of identification bytes in the location to which ptr points. If no data is present, elf is null, or an error occurs, the return value is a null pointer, with zero optionally stored through ptr.
The elf_begin (elf_begin Subroutine) subroutine, elf_kind (elf_kind Subroutine) subroutine, elf_rawfile (elf_rawfile Subroutine) subroutine.
Introduction to ELF Subroutines.