AR(6)AR(6)
NAME
ar – archive (library) file format
SYNOPSIS
#include <ar.h>
DESCRIPTION
The archive command
ar(1)
is used to combine several files into
one.
Archives are used mainly as libraries to be searched
by the loaders
2l(1)
et al.
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:
unhandled troff command .ec
#define ARMAG "!<arch>\n"
#define SARMAG 8
#define ARFMAG "`\n"
struct ar_hdr {
char name[16];
char date[12];
char uid[6];
char gid[6];
char mode[8];
char size[10];
char fmag[2];
};
#define SAR_HDR 60
unhandled troff command .ec
The
name
is a blank-padded string.
The
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
mode,
which is octal.
The date is the modification date of the file (see
stat(2))
at the time of its insertion into the archive.
The mode is the low 9 bits of the file permission mode.
The length of the header is
SAR_HDR.
Because the
ar_hdr
structure is padded in an architecture-dependent manner,
the structure should never be read or written as a unit;
instead, each field should be read or written independently.
Each file begins on an even (0 mod 2) boundary;
a newline is inserted between files if necessary.
Nevertheless
size
reflects the
actual size of the file exclusive of padding.
When all members of an archive are object files of
the same architecture,
ar
automatically adds an extra file, named
__.SYMDEF,
as the first member of the archive. This file
contains an index used by the loaders to locate all
externally defined text and data symbols in the archive.
There is no provision for empty areas in an archive
file.
SEE ALSO
ar(1),
2l(1),
nm(1),
stat(2)
BUGS
The
uid
and
gid
fields are unused in Plan 9.
They provide compatibility with Unix
ar
format.