ar.h(3HEAD)							      Headers							       ar.h(3HEAD)

NAME

       ar.h, ar - archive file format

SYNOPSIS

       #include <ar.h>

DESCRIPTION

       The  archive  command ar is used to combine several files into one. Archives are used mainly as libraries to be searched by the link editor
       ld.

       Each archive begins with the archive magic string.

       #define	ARMAG	"!<arch>
"    /* magic string */
       #define	SARMAG	 8	       /* length of magic string */

       Following the archive magic string are the archive file members. Each file member is preceded by a file member header which is of the  fol-
       lowing format:

       #define	ARFMAG	 "`
"	       /* header trailer string */

       struct  ar_hdr		       /* file member header */
       {
	   char    ar_name[16];        /* '/' terminated file member name */
	   char    ar_date[12];        /* file member date */
	   char    ar_uid[6]	       /* file member user identification */
	   char    ar_gid[6]	       /* file member group identification */
	   char    ar_mode[8]	       /* file member mode (octal) */
	   char    ar_size[10];        /* file member size */
	   char    ar_fmag[2];	       /* header trailer string */
       };

       All  information  in  the  file member headers is in printable ASCII. The numeric information contained in the headers is stored as decimal
       numbers (except for ar_mode which is in octal). Thus, if the archive contains printable files, the archive itself is printable.

       If the file member name fits, the ar_name field contains the name directly, and is terminated by a slash (/) and padded with blanks on  the
       right. If the member's name does not fit, ar_name contains a slash (/) followed by a decimal representation of the name's offset in the ar-
       chive string table described below.

       The ar_date field is the modification date of the file at the time of its insertion into the archive. Common format archives can  be  moved
       from system to system as long as the portable archive command ar is used.

       Each  archive  file  member begins on an even byte boundary; a newline is inserted between files if necessary. Nevertheless, the size given
       reflects the actual size of the file exclusive of padding.

       Notice there is no provision for empty areas in an archive file.

       Each archive that contains object files (see  a.out(4)) includes an archive symbol table. This symbol table is used by the link editor	ld
       to determine which archive members must be loaded during the link edit process. The archive symbol table (if it exists) is always the first
       file in the archive (but is never listed) and is automatically created and/or updated by  ar.

       The archive symbol table has a zero length name (that is,  ar_name[0] is '/'),  ar_name[1]==' ', etc.). All ``words'' in this symbol  table
       have  four  bytes,  using  the machine-independent encoding shown below. All machines use the encoding described here for the symbol table,
       even if the machine's ``natural'' byte order is different.

			0	1	2	3
       0x01020304	01	02	03	04

       The contents of this file are as follows:

       1.  The number of symbols.  Length: 4 bytes.

       2.  The array of offsets into the archive file.	Length: 4 bytes * ``the number of symbols''.

       3.  The name string table.  Length: ar_size - 4 bytes * (``the number of symbols'' + 1).

       As an example, the following symbol table defines 4 symbols. The archive member at file offset 114 defines name. The archive member at file
       offset 122 defines object. The archive member at file offset 426 defines function and the archive member at file offset 434 defines name2.

   Example Symbol Table
       Offset	  +0   +1   +2	 +3
		 ___________________
	0	|	  4	    | 4 offset entries
		|___________________|
	4	|	114	    | name
		|___________________|
	8	|	122	    | object
		|___________________|
       12	|	426	    | function
		|___________________|
       16	|	434	    | name2
		|___________________|
       20	|  n | a  | m  | e  |
		|____|____|____|____|
       24	|  | o  | b  | j  |
		|____|____|____|____|
       28	|  e | c  | t  |  |
		|____|____|____|____|
       32	|  f | u  | n  | c  |
		|____|____|____|____|
       36	|  t | i  | o  | n  |
		|____|____|____|____|
       40	|  | n  | a  | m  |
		|____|____|____|____|
       44	|  e | 2  |  |    |
		|____|____|____|____|

       The string table contains exactly as many null terminated strings as there are elements in the offsets array. Each offset from the array is
       associated with the corresponding name from the string table (in order). The names in the string table are all the defined  global  symbols
       found in the common object files in the archive. Each offset is the location of the archive header for the associated symbol.

       If some archive member's name is more than 15 bytes long, a special archive member contains a table of file names, each followed by a slash
       and a new-line. This string table member, if present, will precede all ``normal'' archive members. The special archive symbol table is  not
       a  ``normal''  member,  and  must  be  first  if  it exists. The ar_name entry of the string table's member header holds a zero length name
       ar_name[0]=='/', followed by one trailing slash (ar_name[1]=='/'), followed by blanks (ar_name[2]==' ', etc.).  Offsets into the string ta-
       ble begin at zero. Example ar_name values for short and long file names appear below.

       Offset	+0   +1   +2   +3   +4	 +5   +6   +7	+8   +9
	      __________________________________________________
	0     | f  | i	| l  | e  | _  | n  | a  | m  | e  | _	|
	      |____|____|____|____|____|____|____|____|____|____|
       10     | s  | a	| m  | p  | l  | e  | /  | 
 | l  | o	|
	      |____|____|____|____|____|____|____|____|____|____|
       20     | n  | g	| e  | r  | f  | i  | l  | e  | n  | a	|
	      |____|____|____|____|____|____|____|____|____|____|
       30     | m  | e	| x  | a  | m  | p  | l  | e  | /  | 
 |
	      |____|____|____|____|____|____|____|____|____|____|

	  Member Name				 ar_name
       _______________________________________________________________
       short-name	    | short-name/  | Not in string table
			    |		   |
       file_name_sample     | /0	   | Offset 0 in string table
			    |		   |
       longerfilenamexample | /18	   | Offset 18 in string table
       _____________________|______________|___________________________

SEE ALSO

       ar(1), ld(1), strip(1), a.out(4)

NOTES

       The strip utility will remove all archive symbol entries from the header.  The archive symbol entries must be restored with the -ts options
       of the ar command before the archive can be used with the link editor ld.

SunOS 5.10							    1 Jul 1998							       ar.h(3HEAD)