ARCHIVE_WRITE_DATA(3)  FreeBSD Library Functions Manual  ARCHIVE_WRITE_DATA(3)

NAME
     archive_write_data, archive_write_data_block - functions for creating
     archives

LIBRARY
     Streaming Archive Library (libarchive, -larchive)

SYNOPSIS
     #include <archive.h>

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

     la_ssize_t
     archive_write_data_block(struct archive *, const void *, size_t size,
         int64_t offset);

DESCRIPTION
     archive_write_data()
             Write data corresponding to the header just written.

     archive_write_data_block()
             Write data corresponding to the header just written.  This is
             like archive_write_data() except that it performs a seek on the
             file being written to the specified offset before writing the
             data.  This is useful when restoring sparse files from archive
             formats that support sparse files.  Returns number of bytes
             written or -1 on error.  (Note: This is currently not supported
             for archive_write handles, only for archive_write_disk handles.

RETURN VALUES
     This function returns the number of bytes actually written, or a negative
     error code on error.

ERRORS
     Detailed error codes and textual descriptions are available from the
     archive_errno() and archive_error_string() functions.

BUGS
     In libarchive 3.x, this function sometimes returns zero on success
     instead of returning the number of bytes written.  Specifically, this
     occurs when writing to an archive_write_disk handle.  Clients should
     treat any value less than zero as an error and consider any non-negative
     value as success.

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

FreeBSD 13.1-RELEASE-p6        February 28, 2017       FreeBSD 13.1-RELEASE-p6