AR(5,F)                     AIX Technical Reference                     AR(5,F)



-------------------------------------------------------------------------------
ar



PURPOSE

Describes common archive file format.

SYNOPSIS

#include <ar.h>

DESCRIPTION

The ar (archive) command is used to combine several files into one.  The ar
command creates an ar file.  The ld (link editor) searches archive files to
resolve program linkage.

Each archive begins with the archive magic string:

     #define ARMAG  "!<arch>\n"   /* magic string */
     #define SARMAG  8            /* length of magic string */

Each archive that contains common object files includes an archive symbol
table.  See "a.out" for the format of an object file.  ld uses this symbol
table to determine the archive members to load during the link edit process.
The archive symbol table, if it exists, is always the first file in the
archive.  It is never listed, but ar automatically creates and updates it.

The archive file members follow the archive header and symbol table.  A file
member follows each file member header.  The format of a file member header is:

     #define ARFMAG    "\n"      /* header trailer string */

     struct ar_hdr {       /* file member header */
       char  ar_name[16];  /* file member name - terminated by '/'*/
       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 */
       char  ar_size[10];  /* file member size */
       char  ar_fmag[2];   /* ARFMAG - string to end header */
     };

All information in the file member header is in printable ASCII.  The numeric
information contained in the headers is stored as decimal numbers, except
ar_mode, which is stored in octal.  Thus, if the archive contains printable
files, you can print the archive.






Processed November 7, 1990          AR(5,F)                                   1

AR(5,F)                     AIX Technical Reference                     AR(5,F)



The ar_name field is blank-padded and terminated by a / (slash).  The ar_date
field indicates the date the file was last modified prior to archive.  The ar
command allows archives to move from system to system.

Each archive file member begins on an even-byte boundary.  ar inserts null
bytes for padding and a new-line character between files, if necessary.  The
ar_size field is the size of the file without padding.  An archive file
contains no empty areas.

If the archive symbol table exists, the first file in the archive has a
zero-length name, for example, ar_name[0] == '/'.  The contents of the symbol
table are as follows:

   The number of symbols.  This is 4 bytes long.

   The array of offsets into the archive file.  The length is determined by 4
   bytes times the number of symbols.

   The name string table.  The size is determined by ar_size minus (4 bytes
   times (the number of symbols plus 1)).

The sgetl and sputl functions manage the number of symbols and the array of
offsets.  The string table contains an equal number of null-terminated strings
and elements in the offsets array.  Each offset from the array associates with
the corresponding name from the string table, in order.  The string table names
all the defined global symbols found in the object files contained in the
archive.  Each offset locates the archive header for the associated symbol.

RELATED INFORMATION

In this book:  "sputl, sgetl" and "a.out."

The ar, ld, and strip commands in AIX Operating System Commands Reference.






















Processed November 7, 1990          AR(5,F)                                   2