146 lines
5.5 KiB
Groff
146 lines
5.5 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ar.5.5 8.1 (Berkeley) 6/9/93
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.\"
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.Dd June 9, 1993
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.Dt AR 5
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.Os
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.Sh NAME
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.Nm ar
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.Nd archive (library) file format
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.Sh SYNOPSIS
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.Fd #include <ar.h>
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.Sh DESCRIPTION
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The archive command
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.Nm ar
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combines several files into one.
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Archives are mainly used as libraries of object files intended to be
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loaded using the link-editor
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.Xr ld 1 .
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.Pp
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A file created with
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.Nm ar
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begins with the ``magic'' string "!<arch>\en".
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The rest of the archive is made up of objects, each of which is composed
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of a header for a file, a possible file name, and the file contents.
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The header is portable between machine architectures, and, if the file
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contents are printable, the archive is itself printable.
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.Pp
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The header is made up of six variable length
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.Tn ASCII
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fields, followed by a
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two character trailer.
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The fields are the object name (16 characters), the file last modification
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time (12 characters), the user and group id's (each 6 characters), the file
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mode (8 characters) and the file size (10 characters).
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All numeric fields are in decimal, except for the file mode which is in
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octal.
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.Pp
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The modification time is the file
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.Fa st_mtime
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field, i.e.,
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.Dv CUT
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seconds since
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the epoch.
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The user and group id's are the file
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.Fa st_uid
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and
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.Fa st_gid
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fields.
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The file mode is the file
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.Fa st_mode
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field.
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The file size is the file
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.Fa st_size
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field.
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The two-byte trailer is the string "\`\en".
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.Pp
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Only the name field has any provision for overflow.
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If any file name is more than 16 characters in length or contains an
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embedded space, the string "#1/" followed by the
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.Tn ASCII
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length of the
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name is written in the name field.
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The file size (stored in the archive header) is incremented by the length
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of the name.
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The name is then written immediately following the archive header.
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.Pp
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Any unused characters in any of these fields are written as space
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characters.
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If any fields are their particular maximum number of characters in
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length, there will be no separation between the fields.
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.Pp
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Objects in the archive are always an even number of bytes long; files
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which are an odd number of bytes long are padded with a newline (``\en'')
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character, although the size in the header does not reflect this.
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.Sh SEE ALSO
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.Xr ar 1 ,
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.Xr stat 2
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.Sh HISTORY
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There have been at least four
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.Nm ar
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formats.
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The first was denoted by the leading ``magic'' number 0177555 (stored as
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type int).
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These archives were almost certainly created on a 16-bit machine, and
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contain headers made up of five fields.
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The fields are the object name (8 characters), the file last modification
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time (type long), the user id (type char), the file mode (type char) and
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the file size (type unsigned int).
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Files were padded to an even number of bytes.
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.Pp
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The second was denoted by the leading ``magic'' number 0177545 (stored as
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type int).
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These archives may have been created on either 16 or 32-bit machines, and
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contain headers made up of six fields.
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The fields are the object name (14 characters), the file last modification
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time (type long), the user and group id's (each type char), the file mode
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(type int) and the file size (type long).
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Files were padded to an even number of bytes.
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For more information on converting from this format see
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.Xr arcv 8 .
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.Pp
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The current archive format (without support for long character names and
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names with embedded spaces) was introduced in
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.Bx 4.0 .
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The headers were the same as the current format, with the exception that
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names longer than 16 characters were truncated, and names with embedded
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spaces (and often trailing spaces) were not supported.
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It has been extended for these reasons,
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as described above.
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This format first appeared in 4.4BSD.
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.Sh COMPATIBILITY
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No archive format is currently specified by any standard.
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.At V
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has historically distributed archives in a different format from
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all of the above.
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