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
7-15 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 
 7-15         |  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)
30 January 1998
© 1998 The Santa Cruz Operation, Inc. All rights reserved.