AR(4) AR(4)
NAME
ar - common archive 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(1).
Each archive begins with the archive magic string.
#define ARMAG "!<arch>\n" /* magic string */
#define SARMAG 8 /* length of magic string */
Each archive which contains common object files [see
a.out(4)] includes an archive symbol table. This symbol
table is used by the link editor ld(1) to determine which
archive members must be loaded during the link edit process.
The archive symbol table (if it exists) is always the first
file in the archive (but is never listed) and is
automatically created and/or updated by ar.
Following the archive magic string are the archive file
members. Each file member is preceded by a file member
header which is of the following format:
#define ARFMAG "`\n" /* header trailer string */
struct ar_hdr /* file member header */
{
char ar_name[16]; /* '/' terminated file member name */
char ar_date[12]; /* file member date */
char ar_uid[6]; /* file member user identification */
char ar_gid[6]; /* file member group identification */
char ar_mode[8]; /* file member mode (octal) */
char ar_size[10]; /* file member size */
char ar_fmag[2]; /* header trailer string */
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AR(4) AR(4)
};
All information in the file member headers is in printable
ASCII. The numeric information contained in the headers is
stored as decimal numbers (except for ar_mode which is in
octal). Thus, if the archive contains printable files, the
archive itself is printable.
The ar_name field is blank-padded and slash (/) terminated.
The ar_date field is the modification date of the file at
the time of its insertion into the archive. Common format
archives can be moved from system to system as long as the
portable archive command ar(1) is used. Conversion tools
such as convert(1) exist to aid in the transportation of
non-common format archives to this format.
Each archive file member begins on an even byte boundary; a
newline is inserted between files if necessary.
Nevertheless the size given reflects the actual size of the
file exclusive of padding.
Notice there is no provision for empty areas in an archive
file.
If the archive symbol table exists, the first file in the
archive has a zero length name (i.e., arname[0] == '/' ).
The contents of this file are as follows:
⊕ The number of symbols. Length: 4 bytes.
⊕ The array of offsets into the archive file. Length: 4
bytes * ``the number of symbols''.
⊕ The name string table. Length: ar_size - (4 bytes *
(``the number of symbols'' + 1)).
The number of symbols and the array of offsets are managed
with sgetl and sputl. The string table contains exactly as
many null terminated strings as there are elements in the
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offsets array. Each offset from the array is associated
with the corresponding name from the string table (in
order). The names in the string table are all the defined
global symbols found in the common object files in the
archive. Each offset is the location of the archive header
for the associated symbol.
SEE ALSO
ar(1), ld(1), strip(1), sputl(3X), a.out(4).
WARNINGS
Strip(1) will remove all archive symbol entries from the
header. The archive symbol entries must be restored via the
ts option of the ar(1) command before the archive can be
used with the link editor ld(1).
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