NAME

filehdr - file header for common object files

SYNOPSIS

#include <filehdr.h>

DESCRIPTION

Every common object file begins with a 20-byte header. The following C struct declaration is used:

struct  filehdr
{
   unsigned short  f_magic ;   /* magic number */
   unsigned short  f_nscns ;   /* number of sections */
   long            f_timdat ;  /* time & date stamp */
   long            f_symptr ;  /* file ptr to symtab */
   long            f_nsyms ;   /* number of symtab entries */
   unsigned short  f_opthdr ;  /* sizeof(opt and header) */
   unsigned short  f_flags ;   /* flags */
} ;

f_symptr is the byte offset into the file at which the symbol table can be found. Its value can be used as the offset in fseek(3S) to position an I/O stream to the symbol table. The UNIX system optional header is 28 bytes. The valid magic numbers are given below:

#define I386MAGIC  0514   /* i386 Computer */
#define WE32MAGIC  0560   /* 3B2, 3B5, and 3B15 computers */
#define N3BMAGIC   0550   /* 3B20 computer */
#define NTVMAGIC   0551   /* 3B20 computer */

#define VAXWRMAGIC 0570   /* VAX writable text segments */
#define VAXROMAGIC 0575   /* VAX read only sharable
                             text segments */

The value in f_timdat is obtained from the time(2) system call. Flag bits currently defined are:

#define F_RELFLG  0000001   /* relocation entries stripped */
#define F_EXEC    0000002   /* file is executable */
#define F_LNNO    0000004   /* line numbers stripped */
#define F_LSYMS   0000010   /* local symbols stripped */
#define F_AR16WR  0000200   /* 16-bit DEC host */
#define F_AR32WR  0000400   /* 32-bit DEC host */
#define F_AR32W   0001000   /* non-DEC host */
#define F_BM32ID  0160000   /* WE32000 family ID field */
#define F_BM32B   0020000   /* file contains WE 32100 code */
#define F_BM32MAU 0040000   /* file reqs MAU to execute */
#define F_BM32RST 0010000   /* this object file contains restore
                               work around [3B5/3B2 only] */

SEE ALSO

time(2), fseek(3S), a.out(4) The ``Common Object File Format
(COFF)'' chapter in the Programmer's Guide