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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_compress,
     archive_write_set_compression_gzip, archive_write_set_compression_none,
     archive_write_set_compression_program,
     archive_write_set_compressor_options, archive_write_set_format_options,
     archive_write_set_options, 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_free -
     functions for creating archives

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_compress(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_set_format_options(struct archive *, const char *);

     int
     archive_write_set_compressor_options(struct archive *, const char *);

     int
     archive_write_set_options(struct archive *, const char *);

     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_free(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
             compression.  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-
             standard ``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_compress(),
             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_set_compressor_options(),
             archive_write_set_format_options(), archive_write_set_options()
             Specifies options that will be passed to the currently-enabled
             compressor and/or format writer.  The argument is a comma-
             separated list of individual options.  Individual options have
             one of the following forms:
             option=value
                     The option/value pair will be provided to every module.
                     Modules that do not accept an option with this name will
                     ignore it.
             option  The option will be provided to every module with a value
                     of ``1''.
             !option
                     The option will be provided to every module with a NULL
                     value.
             module:option=value, module:option, module:!option
                     As above, but the corresponding option and value will be
                     provided only to modules whose name matches module.
             The return value will be ARCHIVE_OK if any module accepts the
             option, or ARCHIVE_WARN if no module accepted the option, or
             ARCHIVE_FATAL if there was a fatal error while attempting to
             process the option.

             The currently supported options are:
             Compressor gzip
                     compression-level
                             The value is interpreted as a decimal integer
                             specifying the gzip compression level.
             Compressor xz
                     compression-level
                             The value is interpreted as a decimal integer
                             specifying the compression level.
             Format mtree
                     cksum, device, flags, gid, gname, indent, link, md5,
                             mode, nlink, rmd160, sha1, sha256, sha384,
                             sha512, size, time, uid, uname
                             Enable a particular keyword in the mtree output.
                             Prefix with an exclamation mark to disable the
                             corresponding keyword.  The default is equivalent
                             to ``device, flags, gid, gname, link, mode,
                             nlink, size, time, type, uid, uname''.
                     all     Enables all of the above keywords.
                     use-set
                             Enables generation of /set lines that specify
                             default values for the following files and/or
                             directories.
                     indent  XXX needs explanation XXX

     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
             archive.

     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
             filename.  A NULL argument indicates that the output should be
             written 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
             allocated 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_free()
             Invokes archive_write_close() if necessary, then releases all
             resources.  If you need detailed information about
             archive_write_close() failures, you should be careful to call it
             separately, as you cannot obtain error information after
             archive_write_free() returns.
     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
     functions 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, const 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
     callback 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
     processing 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.

           #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_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_free(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
     impossible.  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_free().  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
     vendor-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 11.0-PRERELEASE          May 11, 2008          FreeBSD 11.0-PRERELEASE

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

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