elf_getident(3elf)

elf_getident -- retrieve file identification data

Synopsis

   cc [flag . . . ] file . . . -lelf [library] . . .
   
   #include <libelf.h>
   

   char elf_getident(Elf elf, size_t ptr);

Description

As Intro(3elf) 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's 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

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 elf_kind(3elf)] 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.

References

Intro(3elf), elf_begin(3elf), elf_getehdr(3elf), elf_kind(3elf), elf_rawfile(3elf)