1AR(5)                         File Formats Manual                        AR(5)
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NAME

6       ar - archive (library) file format
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SYNOPSIS

9       #include <ar.h>
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DESCRIPTION

12       The  archive command ar is used to combine several files into one.  Ar‐
13       chives are used mainly as libraries to be searched by  the  link-editor
14       ld.
15
16       A  file produced by ar has a magic number at the start, followed by the
17       constituent files, each preceded by a file header.   The  magic  number
18       and header layout as described in the include file are:
19
20              /* Header describing `ar' archive file format.
21                 Copyright (C) 1996 Free Software Foundation, Inc.
22                 This file is part of the GNU C Library.
23
24                 The GNU C Library is free software; you can redistribute it and/or
25                 modify it under the terms of the GNU Lesser General Public
26                 License as published by the Free Software Foundation; either
27                 version 2.1 of the License, or (at your option) any later version.
28
29                 The GNU C Library is distributed in the hope that it will be useful,
30                 but WITHOUT ANY WARRANTY; without even the implied warranty of
31                 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
32                 Lesser General Public License for more details.
33
34                 You should have received a copy of the GNU Lesser General Public
35                 License along with the GNU C Library; if not, see
36                 <http://www.gnu.org/licenses/>.  */
37
38              #ifndef _AR_H
39              #define _AR_H 1
40
41              #include <sys/cdefs.h>
42
43              /* Archive files start with the ARMAG identifying string.  Then follows a
44                 `struct ar_hdr', and as many bytes of member file data as its `ar_size'
45                 member indicates, for each member file.  */
46
47              #define ARMAG "!<arch>0/* String that begins an archive file.  */
48              #define SARMAG8/* Size of that string.  */
49
50              #define ARFMAG"`0/* String in ar_fmag at end of each header.  */
51
52              __BEGIN_DECLS
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54              struct ar_hdr
55                {
56                  char ar_name[16];/* Member file name, sometimes / terminated. */
57                  char ar_date[12];/* File date, decimal seconds since Epoch.  */
58                  char ar_uid[6], ar_gid[6];/* User and group IDs, in ASCII decimal.  */
59                  char ar_mode[8];/* File mode, in ASCII octal.  */
60                  char ar_size[10];/* File size, in ASCII decimal.  */
61                  char ar_fmag[2];/* Always contains ARFMAG.  */
62                };
63
64              __END_DECLS
65
66              #endif /* ar.h */
67
68       The  name  is  a  null-terminated  string;  the  date is in the form of
69       time(2); the user ID and group ID are numbers; the mode is a  bit  pat‐
70       tern per chmod(2); the size is counted in bytes.
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72       Each  file  begins  on a word boundary; a null byte is inserted between
73       files if necessary.  Nevertheless the size given  reflects  the  actual
74       size of the file exclusive of padding.
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76       Notice there is no provision for empty areas in an archive file.
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SEE ALSO

79       ar(1), ld(1), nm(1)
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BUGS

82       Coding user and group IDs as characters is a botch.
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86                                                                         AR(5)