


      AR(4)                       (bsd 4.2)                       AR(4)



      NAME
           ar - archive (library) file format

      SYNTAX
           #include <ar.h>

      DESCRIPTION
           The archive command ar combines 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,
           followed 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  arf_hdr {/* archive file member header */
                        char   arf_name[16];/* file member name */
                        char   arf_date[12];/* file member date */
                        char   arf_uid[6];/* file member user identification */
                        char   arf_gid[6];/* file member group identification */
                        char   arf_mode[8];/* file member mode */
                        char   arf_size[10];/* file member size */
                        char   arf_fmag[2];/*                 */
                };

           The name is a blank-padded string.  The ar_fmag field
           contains 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.

           Each file begins on an even (0 mod 2) boundary; a new-line
           is inserted between files if necessary.  Nevertheless, the
           size given reflects the actual size of the file exclusive of
           padding.  There is no provision for empty areas in an
           archive file.

           The encoding of the header is the same on UNIX System V
           release 2, bsd 4.1, and bsd 4.2.  If an archive contains
           printable files, the archive itself is printable.

      SEE ALSO
           ar(1), ld(1), nm(1)

      BUGS
           File names lose trailing blanks.  Most software dealing with
           archives takes even an included blank as a name terminator.



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