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ARCHIVE_WRITE(3)       FreeBSD Library Functions Manual	      ARCHIVE_WRITE(3)

NAME
     archive_write -- functions	for creating archives

LIBRARY
     Streaming Archive Library (libarchive, -larchive)

SYNOPSIS
     #include <archive.h>

DESCRIPTION
     These functions provide a complete	API for	creating streaming archive
     files.  The general process is to first create the	struct archive object,
     set any desired options, initialize the archive, append entries, then
     close the archive and release all resources.

   Create archive object
     See archive_write_new(3).

     To	write an archive, you must first obtain	an initialized struct archive
     object from archive_write_new().

   Enable filters and formats, configure block size and	padding
     See archive_write_filter(3), archive_write_format(3) and
     archive_write_blocksize(3).

     You can then modify this object for the desired operations	with the vari-
     ous archive_write_set_XXX() functions.  In	particular, you	will need to
     invoke appropriate	archive_write_add_XXX()	and archive_write_set_XXX()
     functions to enable the corresponding compression and format support.

   Set options
     See archive_read_set_options(3).

   Open	archive
     See archive_write_open(3).

     Once you have prepared the	struct archive object, you call
     archive_write_open() to actually open the archive and prepare it for
     writing.  There are several variants of this function; the	most basic
     expects you to provide pointers to	several	functions that can provide
     blocks of bytes from the archive.	There are convenience forms that allow
     you to specify a filename,	file descriptor, FILE *	object,	or a block of
     memory from which to write	the archive data.

   Produce archive
     See archive_write_header(3) and archive_write_data(3).

     Individual	archive	entries	are written in a three-step process: You first
     initialize	a struct archive_entry structure with information about	the
     new entry.	 At a minimum, you should set the pathname of the entry	and
     provide a struct stat with	a valid	st_mode	field, which specifies the
     type of object and	st_size	field, which specifies the size	of the data
     portion of	the object.

   Release resources
     See archive_write_free(3).

     After all entries have been written, use the archive_write_free() func-
     tion to release all resources.

EXAMPLE
     The following sketch illustrates basic usage of the library.  In this
     example, the callback functions are simply	wrappers around	the standard
     open(2), write(2),	and close(2) system calls.

	   #ifdef __linux__
	   #define _FILE_OFFSET_BITS 64
	   #endif
	   #include <sys/stat.h>
	   #include <archive.h>
	   #include <archive_entry.h>
	   #include <fcntl.h>
	   #include <stdlib.h>
	   #include <unistd.h>

	   struct mydata {
	     const char	*name;
	     int fd;
	   };

	   int
	   myopen(struct archive *a, void *client_data)
	   {
	     struct mydata *mydata = client_data;

	     mydata->fd	= open(mydata->name, O_WRONLY |	O_CREAT, 0644);
	     if	(mydata->fd >= 0)
	       return (ARCHIVE_OK);
	     else
	       return (ARCHIVE_FATAL);
	   }

	   ssize_t
	   mywrite(struct archive *a, void *client_data, const void *buff, size_t n)
	   {
	     struct mydata *mydata = client_data;

	     return (write(mydata->fd, buff, n));
	   }

	   int
	   myclose(struct archive *a, void *client_data)
	   {
	     struct mydata *mydata = client_data;

	     if	(mydata->fd > 0)
	       close(mydata->fd);
	     return (0);
	   }

	   void
	   write_archive(const char *outname, const char **filename)
	   {
	     struct mydata *mydata = malloc(sizeof(struct mydata));
	     struct archive *a;
	     struct archive_entry *entry;
	     struct stat st;
	     char buff[8192];
	     int len;
	     int fd;

	     a = archive_write_new();
	     mydata->name = outname;
	     archive_write_add_filter_gzip(a);
	     archive_write_set_format_ustar(a);
	     archive_write_open(a, mydata, myopen, mywrite, myclose);
	     while (*filename) {
	       stat(*filename, &st);
	       entry = archive_entry_new();
	       archive_entry_copy_stat(entry, &st);
	       archive_entry_set_pathname(entry, *filename);
	       archive_write_header(a, entry);
	       if ((fd = open(*filename, O_RDONLY)) != -1) {
		 len = read(fd,	buff, sizeof(buff));
		 while ( len > 0 ) {
		   archive_write_data(a, buff, len);
		   len = read(fd, buff,	sizeof(buff));
		 }
		 close(fd);
	       }
	       archive_entry_free(entry);
	       filename++;
	     }
	     archive_write_free(a);
	   }

	   int main(int	argc, const char **argv)
	   {
	     const char	*outname;
	     argv++;
	     outname = argv++;
	     write_archive(outname, argv);
	     return 0;
	   }

SEE ALSO
     tar(1), libarchive(3), archive_write_set_options(3), cpio(5), mtree(5),
     tar(5)

HISTORY
     The libarchive library first appeared in FreeBSD 5.3.

AUTHORS
     The libarchive library was	written	by Tim Kientzle	<kientzle@acm.org>.

BUGS
     There are many peculiar bugs in historic tar implementations that may
     cause certain programs to reject archives written by this library.	 For
     example, several historic implementations calculated header checksums
     incorrectly and will thus reject valid archives; GNU tar does not fully
     support pax interchange format; some old tar implementations required
     specific field terminations.

     The default pax interchange format	eliminates most	of the historic	tar
     limitations and provides a	generic	key/value attribute facility for ven-
     dor-defined extensions.  One oversight in POSIX is	the failure to provide
     a standard	attribute for large device numbers.  This library uses
     ``SCHILY.devminor'' and ``SCHILY.devmajor'' for device numbers that
     exceed the	range supported	by the backwards-compatible ustar header.
     These keys	are compatible with Joerg Schilling's star archiver.  Other
     implementations may not recognize these keys and will thus	be unable to
     correctly restore device nodes with large device numbers from archives
     created by	this library.

FreeBSD	9.2		       February	2, 2012			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | EXAMPLE | SEE ALSO | HISTORY | AUTHORS | BUGS

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