AR(5) AR(5)
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 link-editor ld.
A file produced by ar has a magic string at the start, fol-
lowed 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];
};
#define SAR_HDR 60
The name is a blank-padded string. The `ar_fmag' field con-
tains `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. The length of the header is
`SAR_HDR'. Because `struct ar_hdr' may be padded on some
machines, `SAR_HDR' should be used in preference to
`sizeof(struct ar_hdr)' when reading and writing file head-
ers.
Each file begins on an even (0 mod 2) boundary; a newline is
inserted between files if necessary. Nevertheless ar_size
reflects the actual size of the file exclusive of padding.
There is no provision for empty areas in an archive file.
If an archive contains only printable files, the archive
AR(5) AR(5)
itself is printable.
SEE ALSO
ar(1), ld(1), nm(1)
BUGS
File names lose trailing blanks.
Most software that deals with archives takes an embedded
blank as a name terminator.