Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
archive_write(3)       FreeBSD Library Functions Manual	      archive_write(3)

NAME
     archive_write_new,	archive_write_set_format_cpio,
     archive_write_set_format_pax, archive_write_set_format_pax_restricted,
     archive_write_set_format_shar, archive_write_set_format_shar_binary,
     archive_write_set_format_ustar, archive_write_get_bytes_per_block,
     archive_write_set_bytes_per_block,	archive_write_set_bytes_in_last_block,
     archive_write_set_compression_bzip2, archive_write_set_compression_gzip,
     archive_write_set_compression_none,
     archive_write_set_compression_program, archive_write_open,
     archive_write_open_fd, archive_write_open_FILE,
     archive_write_open_filename, archive_write_open_memory,
     archive_write_header, archive_write_data, archive_write_finish_entry,
     archive_write_close, archive_write_finish -- functions for	creating ar-
     chives

SYNOPSIS
     #include <archive.h>

     struct archive *
     archive_write_new(void);

     int
     archive_write_get_bytes_per_block(struct archive *);

     int
     archive_write_set_bytes_per_block(struct archive *, int bytes_per_block);

     int
     archive_write_set_bytes_in_last_block(struct archive *, int);

     int
     archive_write_set_compression_bzip2(struct	archive	*);

     int
     archive_write_set_compression_gzip(struct archive *);

     int
     archive_write_set_compression_none(struct archive *);

     int
     archive_write_set_compression_program(struct archive *,
	 const char * cmd);

     int
     archive_write_set_format_cpio(struct archive *);

     int
     archive_write_set_format_pax(struct archive *);

     int
     archive_write_set_format_pax_restricted(struct archive *);

     int
     archive_write_set_format_shar(struct archive *);

     int
     archive_write_set_format_shar_binary(struct archive *);

     int
     archive_write_set_format_ustar(struct archive *);

     int
     archive_write_open(struct archive *, void *client_data,
	 archive_open_callback *, archive_write_callback *,
	 archive_close_callback	*);

     int
     archive_write_open_fd(struct archive *, int fd);

     int
     archive_write_open_FILE(struct archive *, FILE *file);

     int
     archive_write_open_filename(struct	archive	*, const char *filename);

     int
     archive_write_open_memory(struct archive *, void *buffer,
	 size_t	bufferSize, size_t *outUsed);

     int
     archive_write_header(struct archive *, struct archive_entry *);

     ssize_t
     archive_write_data(struct archive *, const	void *,	size_t);

     int
     archive_write_finish_entry(struct archive *);

     int
     archive_write_close(struct	archive	*);

     int
     archive_write_finish(struct archive *);

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.  The following summary
     describes the functions in	approximately the order	they are ordinarily
     used:

     archive_write_new()
	     Allocates and initializes a struct	archive	object suitable	for
	     writing a tar archive.

     archive_write_set_bytes_per_block()
	     Sets the block size used for writing the archive data.  Every
	     call to the write callback	function, except possibly the last
	     one, will use this	value for the length.  The third parameter is
	     a boolean that specifies whether or not the final block written
	     will be padded to the full	block size.  If	it is zero, the	last
	     block will	not be padded.	If it is non-zero, padding will	be
	     added both	before and after compression.  The default is to use a
	     block size	of 10240 bytes and to pad the last block.  Note	that a
	     block size	of zero	will suppress internal blocking	and cause
	     writes to be sent directly	to the write callback as they occur.

     archive_write_get_bytes_per_block()
	     Retrieve the block	size to	be used	for writing.  A	value of -1
	     here indicates that the library should use	default	values.	 A
	     value of zero indicates that internal blocking is suppressed.

     archive_write_set_bytes_in_last_block()
	     Sets the block size used for writing the last block.  If this
	     value is zero, the	last block will	be padded to the same size as
	     the other blocks.	Otherwise, the final block will	be padded to a
	     multiple of this size.  In	particular, setting it to 1 will cause
	     the final block to	not be padded.	For compressed output, any
	     padding generated by this option is applied only after the	com-
	     pression.	The uncompressed data is always	unpadded.  The default
	     is	to pad the last	block to the full block	size (note that
	     archive_write_open_filename() will	set this based on the file
	     type).  Unlike the	other ``set'' functions, this function can be
	     called after the archive is opened.

     archive_write_get_bytes_in_last_block()
	     Retrieve the currently-set	value for last block size.  A value of
	     -1	here indicates that the	library	should use default values.

     archive_write_set_format_cpio(), archive_write_set_format_pax(),
	     archive_write_set_format_pax_restricted(),
	     archive_write_set_format_shar(),
	     archive_write_set_format_shar_binary(),
	     archive_write_set_format_ustar()
	     Sets the format that will be used for the archive.	 The library
	     can write POSIX octet-oriented cpio format	archives, POSIX-stan-
	     dard ``pax	interchange'' format archives, traditional ``shar''
	     archives, enhanced	``binary'' shar	archives that store a variety
	     of	file attributes	and handle binary files, and POSIX-standard
	     ``ustar'' archives.  The pax interchange format is	a backwards-
	     compatible	tar format that	adds key/value attributes to each
	     entry and supports	arbitrary filenames, linknames,	uids, sizes,
	     etc.  ``Restricted	pax interchange	format'' is the	library
	     default; this is the same as pax format, but suppresses the pax
	     extended header for most normal files.  In	most cases, this will
	     result in ordinary	ustar archives.

     archive_write_set_compression_bzip2(),
	     archive_write_set_compression_gzip(),
	     archive_write_set_compression_none()
	     The resulting archive will	be compressed as specified.  Note that
	     the compressed output is always properly blocked.

     archive_write_set_compression_program()
	     The archive will be fed into the specified	compression program.
	     The output	of that	program	is blocked and written to the client
	     write callbacks.

     archive_write_open()
	     Freeze the	settings, open the archive, and	prepare	for writing
	     entries.  This is the most	generic	form of	this function, which
	     accepts pointers to three callback	functions which	will be
	     invoked by	the compression	layer to write the constructed ar-
	     chive.

     archive_write_open_fd()
	     A convenience form	of archive_write_open()	that accepts a file
	     descriptor.  The archive_write_open_fd() function is safe for use
	     with tape drives or other block-oriented devices.

     archive_write_open_FILE()
	     A convenience form	of archive_write_open()	that accepts a FILE *
	     pointer.  Note that archive_write_open_FILE() is not safe for
	     writing to	tape drives or other devices that require correct
	     blocking.

     archive_write_open_file()
	     A deprecated synonym for archive_write_open_filename().

     archive_write_open_filename()
	     A convenience form	of archive_write_open()	that accepts a file-
	     name.  A NULL argument indicates that the output should be	writ-
	     ten to standard output; an	argument of ``-'' will open a file
	     with that name.  If you have not invoked
	     archive_write_set_bytes_in_last_block(), then
	     archive_write_open_filename() will	adjust the last-block padding
	     depending on the file: it will enable padding when	writing	to
	     standard output or	to a character or block	device node, it	will
	     disable padding otherwise.	 You can override this by manually
	     invoking archive_write_set_bytes_in_last_block() before calling
	     archive_write_open().  The	archive_write_open_filename() function
	     is	safe for use with tape drives or other block-oriented devices.

     archive_write_open_memory()
	     A convenience form	of archive_write_open()	that accepts a pointer
	     to	a block	of memory that will receive the	archive.  The final
	     size_t * argument points to a variable that will be updated after
	     each write	to reflect how much of the buffer is currently in use.
	     You should	be careful to ensure that this variable	remains	allo-
	     cated until after the archive is closed.

     archive_write_header()
	     Build and write a header using the	data in	the provided struct
	     archive_entry structure.  See archive_entry(3) for	information on
	     creating and populating struct archive_entry objects.

     archive_write_data()
	     Write data	corresponding to the header just written.  Returns
	     number of bytes written or	-1 on error.

     archive_write_finish_entry()
	     Close out the entry just written.	In particular, this writes out
	     the final padding required	by some	formats.  Ordinarily, clients
	     never need	to call	this, as it is called automatically by
	     archive_write_next_header() and archive_write_close() as needed.

     archive_write_close()
	     Complete the archive and invoke the close callback.

     archive_write_finish()
	     Invokes archive_write_close() if it was not invoked manually,
	     then releases all resources.  Note	that this function was
	     declared to return	void in	libarchive 1.x,	which made it impossi-
	     ble to detect errors when archive_write_close() was invoked
	     implicitly	from this function.  This is corrected beginning with
	     libarchive	2.0.
     More information about the	struct archive object and the overall design
     of	the library can	be found in the	libarchive(3) overview.

IMPLEMENTATION
     Compression support is built-in to	libarchive, which uses zlib and	bzlib
     to	handle gzip and	bzip2 compression, respectively.

CLIENT CALLBACKS
     To	use this library, you will need	to define and register callback	func-
     tions that	will be	invoked	to write data to the resulting archive.	 These
     functions are registered by calling archive_write_open():

	   typedef int archive_open_callback(struct archive *, void
	   *client_data)

     The open callback is invoked by archive_write_open().  It should return
     ARCHIVE_OK	if the underlying file or data source is successfully opened.
     If	the open fails,	it should call archive_set_error() to register an
     error code	and message and	return ARCHIVE_FATAL.

	   typedef ssize_t archive_write_callback(struct archive *, void
	   *client_data, void *buffer, size_t length)

     The write callback	is invoked whenever the	library	needs to write raw
     bytes to the archive.  For	correct	blocking, each call to the write call-
     back function should translate into a single write(2) system call.	 This
     is	especially critical when writing archives to tape drives.  On success,
     the write callback	should return the number of bytes actually written.
     On	error, the callback should invoke archive_set_error() to register an
     error code	and message and	return -1.

	   typedef int archive_close_callback(struct archive *,	void
	   *client_data)

     The close callback	is invoked by archive_close when the archive process-
     ing is complete.  The callback should return ARCHIVE_OK on	success.  On
     failure, the callback should invoke archive_set_error() to	register an
     error code	and message and	return ARCHIVE_FATAL.

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.

	   #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, 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_set_compression_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);
	       fd = open(*filename, O_RDONLY);
	       len = read(fd, buff, sizeof(buff));
	       while ( len > 0 ) {
		   archive_write_data(a, buff, len);
		   len = read(fd, buff,	sizeof(buff));
	       }
	       archive_entry_free(entry);
	       filename++;
	     }
	     archive_write_finish(a);
	   }

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

RETURN VALUES
     Most functions return ARCHIVE_OK (zero) on	success, or one	of several
     non-zero error codes for errors.  Specific	error codes include:
     ARCHIVE_RETRY for operations that might succeed if	retried, ARCHIVE_WARN
     for unusual conditions that do not	prevent	further	operations, and
     ARCHIVE_FATAL for serious errors that make	remaining operations impossi-
     ble.  The archive_errno() and archive_error_string() functions can	be
     used to retrieve an appropriate error code	and a textual error message.

     archive_write_new() returns a pointer to a	newly-allocated	struct archive
     object.

     archive_write_data() returns a count of the number	of bytes actually
     written.  On error, -1 is returned	and the	archive_errno()	and
     archive_error_string() functions will return appropriate values.  Note
     that if the client-provided write callback	function returns a non-zero
     value, that error will be propagated back to the caller through whatever
     API function resulted in that call, which may include
     archive_write_header(), archive_write_data(), archive_write_close(), or
     archive_write_finish().  The client callback can call archive_set_error()
     to	provide	values that can	then be	retrieved by archive_errno() and
     archive_error_string().

SEE ALSO
     tar(1), libarchive(3), 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	10.1			August 19, 2006			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION | CLIENT CALLBACKS | EXAMPLE | RETURN VALUES | SEE ALSO | HISTORY | AUTHORS | BUGS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=archive_write&sektion=3&manpath=FreeBSD+6.3-RELEASE>

home | help