Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

ar(5) [v7 man page]

AR(5)								File Formats Manual							     AR(5)

ar - archive (library) file format SYNOPSIS
#include <ar.h> DESCRIPTION
The archive command ar 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 number 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: /* Header describing `ar' archive file format. Copyright (C) 1996-2018 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see <>. */ #ifndef _AR_H #define _AR_H 1 #include <sys/cdefs.h> /* Archive files start with the ARMAG identifying string. Then follows a `struct ar_hdr', and as many bytes of member file data as its `ar_size' member indicates, for each member file. */ #define ARMAG "!<arch>0/* String that begins an archive file. */ #define SARMAG8/* Size of that string. */ #define ARFMAG"`0/* String in ar_fmag at end of each header. */ __BEGIN_DECLS struct ar_hdr { char ar_name[16];/* Member file name, sometimes / terminated. */ char ar_date[12];/* File date, decimal seconds since Epoch. */ char ar_uid[6], ar_gid[6];/* User and group IDs, in ASCII decimal. */ char ar_mode[8];/* File mode, in ASCII octal. */ char ar_size[10];/* File size, in ASCII decimal. */ char ar_fmag[2];/* Always contains ARFMAG. */ }; __END_DECLS #endif /* ar.h */ The name is a null-terminated string; the date is in the form of time(2); the user ID and group ID are numbers; the mode is a bit pattern per chmod(2); the size is counted in bytes. Each file begins on a word boundary; a null byte 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. SEE ALSO
ar(1), ld(1), nm(1) BUGS
Coding user and group IDs as characters is a botch. AR(5)

Check Out this Related Man Page

ar.h(3HEAD)							      Headers							       ar.h(3HEAD)

ar.h, ar - archive file format SYNOPSIS
#include <ar.h> DESCRIPTION
The archive command ar is used to combine several files into one. Archives are used mainly as libraries to be searched by the link editor ld. Each archive begins with the archive magic string. #define ARMAG "!<arch> " /* magic string */ #define SARMAG 8 /* length of magic string */ Following the archive magic string are the archive file members. Each file member is preceded by a file member header which is of the fol- lowing format: #define ARFMAG "` " /* 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 */ }; 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. If the file member name fits, the ar_name field contains the name directly, and is terminated by a slash (/) and padded with blanks on the right. If the member's name does not fit, ar_name contains a slash (/) followed by a decimal representation of the name's offset in the ar- chive string table described below. 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 is used. 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. Each archive that contains object files (see a.out(4)) includes an archive symbol table. This symbol table is used by the link editor ld 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. The archive symbol table has a zero length name (that is, ar_name[0] is '/'), ar_name[1]==' ', etc.). All ``words'' in this symbol table have four bytes, using the machine-independent encoding shown below. All machines use the encoding described here for the symbol table, even if the machine's ``natural'' byte order is different. 0 1 2 3 0x01020304 01 02 03 04 The contents of this file are as follows: 1. The number of symbols. Length: 4 bytes. 2. The array of offsets into the archive file. Length: 4 bytes * ``the number of symbols''. 3. The name string table. Length: ar_size - 4 bytes * (``the number of symbols'' + 1). As an example, the following symbol table defines 4 symbols. The archive member at file offset 114 defines name. The archive member at file offset 122 defines object. The archive member at file offset 426 defines function and the archive member at file offset 434 defines name2. Example Symbol Table Offset +0 +1 +2 +3 ___________________ 0 | 4 | 4 offset entries |___________________| 4 | 114 | name |___________________| 8 | 122 | object |___________________| 12 | 426 | function |___________________| 16 | 434 | name2 |___________________| 20 | n | a | m | e | |____|____|____|____| 24 | | o | b | j | |____|____|____|____| 28 | e | c | t | | |____|____|____|____| 32 | f | u | n | c | |____|____|____|____| 36 | t | i | o | n | |____|____|____|____| 40 | | n | a | m | |____|____|____|____| 44 | e | 2 | | | |____|____|____|____| The string table contains exactly as many null terminated strings as there are elements in the 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. If some archive member's name is more than 15 bytes long, a special archive member contains a table of file names, each followed by a slash and a new-line. This string table member, if present, will precede all ``normal'' archive members. The special archive symbol table is not a ``normal'' member, and must be first if it exists. The ar_name entry of the string table's member header holds a zero length name ar_name[0]=='/', followed by one trailing slash (ar_name[1]=='/'), followed by blanks (ar_name[2]==' ', etc.). Offsets into the string ta- ble begin at zero. Example ar_name values for short and long file names appear below. Offset +0 +1 +2 +3 +4 +5 +6 +7 +8 +9 __________________________________________________ 0 | f | i | l | e | _ | n | a | m | e | _ | |____|____|____|____|____|____|____|____|____|____| 10 | s | a | m | p | l | e | / | | l | o | |____|____|____|____|____|____|____|____|____|____| 20 | n | g | e | r | f | i | l | e | n | a | |____|____|____|____|____|____|____|____|____|____| 30 | m | e | x | a | m | p | l | e | / | | |____|____|____|____|____|____|____|____|____|____| Member Name ar_name _______________________________________________________________ short-name | short-name/ | Not in string table | | file_name_sample | /0 | Offset 0 in string table | | longerfilenamexample | /18 | Offset 18 in string table _____________________|______________|___________________________ SEE ALSO
ar(1), ld(1), strip(1), a.out(4) NOTES
The strip utility will remove all archive symbol entries from the header. The archive symbol entries must be restored with the -ts options of the ar command before the archive can be used with the link editor ld. SunOS 5.10 1 Jul 1998 ar.h(3HEAD)
Man Page