ar(4)

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:

          #define ARMAG  "!<arch>\n"
          #define SARMAG 8
          #define ARFMAG "`\n"

          struct ar_hdr
          {
                  char   ar_name[16];
                  char   ar_date[12];
                  char   ar_uid[6];
                  char   ar_gid[6];
                  char   ar_mode[8];
                  char   ar_size[10];
                  char   ar_fmag[2];
          };
          typedef struct ar_hdr ARHDR;

     The name is terminated with a "/" character by default.  Any remaining
     room in the name field is blank_filled.

     File names can be any length: they re not limited to 15 characters.  For
     additional details, see the ABI book mentioned below and the ar(1) man
     page.

     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.  With compiler releases
     7.0 and lower, a new-line is inserted between files if necessary.  The
     size given reflects the actual size of the file exclusive of padding.
     With compiler releases 7.1 and higher, in order to guarantee that each
     ELF format file is 16-byte aligned in the archive, additional padding has
     been added to the end of each file to achieve that, using the character
     '\0'.  This enables the loader (ld) to have faster access to members in
     the archive while performing static linking.  This results in the change
     of size of files permanently, normally increased by 1 to 15 bytes.  With
     non-ELF files, this padding would not occur.

     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),

     System V Application Binary Interface, ISBN 0-13-877598-2, Prentice Hall
     System V ABI MIPS Processor Supplement, ISBN 0-13-880170-3, Prentice Hall