FILEHDR(5)                           BSD                            FILEHDR(5)



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;  /* # symtab entries */
            unsigned short  f_opthdr; /* sizeof(opt hdr) */
            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:

            /* Apollo 68000-based machines */
          #define APOLLOM68KMAGIC     0627

            /* Apollo A88K-based machines */
          #define APOLLOA88KMAGIC     0624

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

     #define  F_RELFLG      0000001  /* relocation info stripped */
     #define  F_EXEC        0000002  /* file is executable */
     #define  F_LNNO        0000004  /* line nunbers stripped */
     #define  F_LSYMS       0000010  /* local symbols stripped */
     #define  F_MINMAL      0000020  /* minimal object file (fextract) */
     #define  F_UPDATE      0000040  /* fully bound update file (ogen) */
     #define  F_SWABD       0000100  /* has had its bytes swabbed (in names) */
     #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_PATCH       0002000  /* "patch" list in optional header */
     #define  F_NODF        0002000  /* (minimal file only) no decision functions */
                                     /* for replaced functions */
     #define  F_BREAKPOINT  0020000  /* contains breakpoints inserted by debugger */
     #define  F_STRIPPED    0040000  /* stripped of unneeded symbols and strings */
     #define  F_PIC         0100000  /* contains position-independent code */

SEE ALSO
     time(2), fseek(3S), a.out(5).