4.3BSD - /usr/man/cat5/ar.0

AR(5)                                                                    AR(5)


NAME
       ar - archive (library) file format

SYNOPSIS
       #include <ar.h>

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

       A file produced by ar has a magic string at the start, followed by  the
       constituent  files,  each  preceded by a file header.  The magic number
       and header layout as described in the include file are:

              /* Header describing ‘ar’ archive file format.
                 Copyright (C) 1996 Free Software Foundation, Inc.
                 This file is part of the GNU C Library.

                 The GNU C Library is free software; you can redistribute it and/or
                 modify it under the terms of the GNU Lesser General Public
                 License as published by the Free Software Foundation; either
                 version 2.1 of the License, or (at your option) any later version.

                 The GNU C Library is distributed in the hope that it will be useful,
                 but WITHOUT ANY WARRANTY; without even the implied warranty of
                 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
                 Lesser General Public License for more details.

                 You should have received a copy of the GNU Lesser General Public
                 License along with the GNU C Library; if not, write to the Free
                 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
                 02111-1307 USA.  */

              #ifndef _AR_H
              #define _AR_H 1

              #include <sys/cdefs.h>

              /* Archive files start with the ARMAG identifying string.  Then follows a
                 ‘struct ar_hdr’, and as many bytes of member file data as its ‘ar_size’
                 member indicates, for each member file.  */

              #define ARMAG  "!<arch>\n"/* String that begins an archive file.  */
              #define SARMAG 8/* Size of that string.  */

              #define ARFMAG "‘\n"/* String in ar_fmag at end of each header.  */

              __BEGIN_DECLS

              struct ar_hdr
                {
                  char ar_name[16];/* Member file name, sometimes / terminated. */
                  char ar_date[12];/* File date, decimal seconds since Epoch.  */
                  char ar_uid[6], ar_gid[6];/* User and group IDs, in ASCII decimal.  */
                  char ar_mode[8];/* File mode, in ASCII octal.  */
                  char ar_size[10];/* File size, in ASCII decimal.  */
                  char ar_fmag[2];/* Always contains ARFMAG.  */
                };

              __END_DECLS

              #endif /* ar.h */

       The name is a blank-padded string.  The ar_fmag field  contains  ARFMAG
       to  help  verify  the presence of a header.  The other fields are left-
       adjusted, blank-padded numbers.  They are decimal except  for  ar_mode,
       which  is  octal.  The date is the modification date of the file at the
       time of its insertion into the archive.

       Each file begins on a even (0 mod 2) boundary; a new-line  is  inserted
       between  files  if necessary.  Nevertheless the size given reflects the
       actual size of the file exclusive of padding.

       There is no provision for empty areas in an archive file.

       The encoding of the header is portable across machines.  If an  archive
       contains printable files, the archive itself is printable.

SEE ALSO
       ar(1), ld(1), nm(1)

BUGS
       File  names  lose trailing blanks.  Most software dealing with archives
       takes even an included blank as a name terminator.


7th Edition                      May 15, 1985                            AR(5)