'\"macro stdmacro
.if n .pH g4.ar @(#)ar	40.10 of 10/27/89
.\" Copyright 1989 AT&T
.nr X
.if \nX=0 .ds x} ar 4 "" "\&"
.if \nX=1 .ds x} ar 4 ""
.if \nX=2 .ds x} ar 4 "" "\&"
.if \nX=3 .ds x} ar "" "" "\&"
.TH \*(x}
.SH NAME
\f4ar\f1 \-  archive file format
.SH SYNOPSIS
\f4#include <ar.h>\f1
.SH DESCRIPTION
The archive command
\f4ar\fP
is used to combine several files into
one.
Archives are used mainly as libraries to be searched
by the link editor
\f4ld\fP.
.PP
Each archive begins with the archive magic string.
.nf
.ft4
.ds HZ #definexx\s-1ARMAG\s+1xxx#M<arch>/n#xxx

#define  \s-1ARMAG\s+1   "\^!<arch>\en"\h'|\w'\*(HZ'u'/\(** magic string \(**/
#define  \s-1SARMAG\s+1  8\h'|\w'\*(HZ'u'/\(** length of magic string \(**/

.ft1
.fi
.PP
Following the archive magic string are the archive file members.
Each file member is preceded by a file member header which is of the following
format:
.nf
.ft4
.ds HZ #definexx\s-1ARFMAG\s+1xxx#M/n#xxx
.sp .75
#define  \s-1ARFMAG\s+1    "\^\(ga\^\en"\h\(ga|\w'\*(HZ'u'/\(** header trailer string \(**/
.sp .75
struct  ar_hdr\h'|\w'\*(HZ'u'/\(** file member header \(**/
{
    char    ar_name[16];\h'|\w'\*(HZ'u'/\(** '/' terminated file member name \(**/
    char    ar_date[12];\h'|\w'\*(HZ'u'/\(** file member date \(**/
    char    ar_uid[6];\h'|\w'\*(HZ'u'/\(** file member user identification \(**/
    char    ar_gid[6];\h'|\w'\*(HZ'u'/\(** file member group identification \(**/
    char    ar_mode[8];\h'|\w'\*(HZ'u'/\(** file member mode (octal) \(**/
    char    ar_size[10];\h'|\w'\*(HZ'u'/\(** file member size \(**/
    char    ar_fmag[2];\h'|\w'\*(HZ'u'/\(** header trailer string \(**/
};

.ft1
.fi
.PP
All information in the file member headers is in printable
.SM ASCII.
The numeric information contained in the headers is stored as
decimal numbers (except for
.I ar_mode\^
which is in octal).
Thus, if the archive contains printable files, the archive itself is printable.
.PP
If the file member name fits,
the
.I ar_name\^
field contains the name directly,
and is terminated by a slash (\f4/\f1) and
padded with blanks on the right.
If the member's name does not fit,
.I ar_name
contains a slash (\f4/\f1)
followed by a decimal representation of the name's offset
in the archive string table described below.
.PP
The
.I 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
\f4ar\fP
is used.
.ne3
.PP
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.
.PP
Notice there is no provision for empty areas in an archive
file.
.PP
Each archive that contains object files [see \f4a.out\f1(4)] includes
an archive symbol table.
This symbol table is used by the link editor \f4ld\f1 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 \f4ar\f1.
.PP
The archive symbol table has a zero length name (i.e., \f4ar_name[0]\f1
is \f4'/'\f1), \f4ar_name[1]==' '\f1, 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.)
.TS
center;
l l l l l
l0p-2f4w(1i) | l0p-2w(.5i) | l0p-2w(.5i) | l0p-2w(.5i) | l0p-2w(.5i)|.
	_	_	_	_
	0	1	2	3
.T&
l0f4w(1i) | c0w(.5i) | c0w(.5i) | c0w(.5i) | c0w(.5i)|.
0x01020304	01	02	03	04
.sp .75
	_	_	_	_
.TE
.PP
The contents of this file are as follows:
.TP
1.
The number of symbols.  Length: 4 bytes.
.TP
2.
The array of offsets into the archive file.  Length: 4 bytes \(** ``the
number of symbols''.
.TP
3.
The name string table.  Length:
.I ar_size\^
\- 4 bytes \(** (``the number of symbols'' + 1).
.PP
As an example, the following symbol table defines
4 symbols.
The archive member at file offset 114 defines
\f4name\f1
and
\f4object\f1.
The archive member at file offset 426 defines
\f4function\f1
and a second version of
\f4name\f1.
.FG "Example Symbol Table"
.TS
center;
c c c c c c
n | cf(CW) s s s| l.
Offset	+0	+1	+2	+3
	_
0	4	4 offset entries
	_
4	114	\f(CWname\fP
	_
8	114	\f(CWobject\fP
	_
12	426	\f(CWfunction\fP
	_
16	426	\f(CWname\fP
	_
.T&
n  | cf(CW) | cf(CW) | cf(CW) | cf(CW) | l.
20	n	a	m	e
	_	_	_	_
24	\e0	o	b	j
	_	_	_	_
28	e	c	t	\e0
	_	_	_	_
32	f	u	n	c
	_	_	_	_
36	t	i	o	n
	_	_	_	_
40	\e0	n	a	m
	_	_	_	_
44	e	\e0
	_	_	_	_
.TE
.PP
The number of symbols and the array of offsets are managed with
\f4sgetl\fP and \f4sputl\f1.
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.
.PP
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
\f2ar_name\f1
entry of the string table's member header holds a zero length name
\f4ar_name[0]=='/'\f1,
followed by one trailing slash
(\f4ar_name[1]=\^='/'\fP),
followed by blanks
(\f4ar_name[2]=\^='\ '\fP, etc.).
Offsets into the string table begin at zero.
Example
\f2ar_name\f1
values for short and long file names appear below.
.br
.ne 3i
.TS
center;
c c c c c c c c c c c
n | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e | cf(CW)e|.
Offset	+0	+1	+2	+3	+4	+5	+6	+7	+8	+9
	_	_	_	_	_	_	_	_	_	_
0	f	i	l	e	\0_\0	n	a	m	e	\0_\0
	_	_	_	_	_	_	_	_	_	_
10	s	a	m	p	l	e	/	\en	l	o
	_	_	_	_	_	_	_	_	_	_
20	n	g	e	r	f	i	l	e	n	a
	_	_	_	_	_	_	_	_	_	_
30	m	e	x	a	m	p	l	e	/	\en
	_	_	_	_	_	_	_	_	_	_
.sp
.T&
c s s s cf2 s s c s s s
lf(CW) s s s | lf(CW) s s | l s s s.
Member Name	ar_name	Note
.sp .3v
_
short-name	short-name/	Not in string table
file_name_sample	/0	Offset 0 in string table
longerfilenamexample	/18	Offset 18 in string table
_
.TE
.SH SEE ALSO
\f4ar\fP(1), \f4ld\fP(1), \f4strip\fP(1),
\f4sputl\fP(3X), \f4a.out\fP(4).
.SH NOTES
\f4strip\fP
will remove all archive symbol entries from the header.  The archive symbol
entries must be restored via the \f4\-ts\f1 options of the
\f4ar\fP
command before the archive can be used with the link editor
\f4ld\fP.
.\"	@(#)ar.4	6.3 of 10/20/83
.Ee




