269 lines
7.3 KiB
Groff
269 lines
7.3 KiB
Groff
.\" Copyright (c) 2003-2011 Tim Kientzle
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 2, 2012
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.Dt ARCHIVE_WRITE 3
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.Os
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.Sh NAME
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.Nm archive_write
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.Nd functions for creating archives
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.Sh LIBRARY
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Streaming Archive Library (libarchive, -larchive)
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.Sh SYNOPSIS
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.In archive.h
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.Sh DESCRIPTION
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These functions provide a complete API for creating streaming
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archive files.
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The general process is to first create the
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.Tn struct archive
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object, set any desired options, initialize the archive, append entries, then
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close the archive and release all resources.
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.\"
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.Ss Create archive object
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See
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.Xr archive_write_new 3 .
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.Pp
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To write an archive, you must first obtain an initialized
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.Tn struct archive
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object from
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.Fn archive_write_new .
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.\"
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.Ss Enable filters and formats, configure block size and padding
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See
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.Xr archive_write_filter 3 ,
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.Xr archive_write_format 3
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and
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.Xr archive_write_blocksize 3 .
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.Pp
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You can then modify this object for the desired operations with the
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various
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.Fn archive_write_set_XXX
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functions.
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In particular, you will need to invoke appropriate
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.Fn archive_write_add_XXX
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and
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.Fn archive_write_set_XXX
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functions to enable the corresponding compression and format
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support.
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.\"
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.Ss Set options
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See
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.Xr archive_read_set_options 3 .
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.\"
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.Ss Open archive
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See
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.Xr archive_write_open 3 .
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.Pp
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Once you have prepared the
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.Tn struct archive
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object, you call
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.Fn archive_write_open
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to actually open the archive and prepare it for writing.
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There are several variants of this function;
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the most basic expects you to provide pointers to several
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functions that can provide blocks of bytes from the archive.
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There are convenience forms that allow you to
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specify a filename, file descriptor,
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.Ft "FILE *"
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object, or a block of memory from which to write the archive data.
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.\"
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.Ss Produce archive
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See
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.Xr archive_write_header 3
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and
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.Xr archive_write_data 3 .
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.Pp
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Individual archive entries are written in a three-step
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process:
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You first initialize a
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.Tn struct archive_entry
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structure with information about the new entry.
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At a minimum, you should set the pathname of the
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entry and provide a
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.Va struct stat
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with a valid
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.Va st_mode
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field, which specifies the type of object and
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.Va st_size
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field, which specifies the size of the data portion of the object.
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.\"
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.Ss Release resources
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See
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.Xr archive_write_free 3 .
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.Pp
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After all entries have been written, use the
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.Fn archive_write_free
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function to release all resources.
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.\"
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.Sh EXAMPLE
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The following sketch illustrates basic usage of the library.
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In this example,
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the callback functions are simply wrappers around the standard
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.Xr open 2 ,
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.Xr write 2 ,
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and
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.Xr close 2
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system calls.
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.Bd -literal -offset indent
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#ifdef __linux__
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#define _FILE_OFFSET_BITS 64
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#endif
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#include <sys/stat.h>
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#include <archive.h>
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#include <archive_entry.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <unistd.h>
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struct mydata {
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const char *name;
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int fd;
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};
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int
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myopen(struct archive *a, void *client_data)
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{
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struct mydata *mydata = client_data;
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mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644);
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if (mydata->fd >= 0)
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return (ARCHIVE_OK);
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else
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return (ARCHIVE_FATAL);
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}
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la_ssize_t
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mywrite(struct archive *a, void *client_data, const void *buff, size_t n)
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{
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struct mydata *mydata = client_data;
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return (write(mydata->fd, buff, n));
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}
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int
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myclose(struct archive *a, void *client_data)
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{
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struct mydata *mydata = client_data;
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if (mydata->fd > 0)
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close(mydata->fd);
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return (0);
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}
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void
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write_archive(const char *outname, const char **filename)
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{
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struct mydata *mydata = malloc(sizeof(struct mydata));
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struct archive *a;
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struct archive_entry *entry;
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struct stat st;
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char buff[8192];
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int len;
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int fd;
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a = archive_write_new();
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mydata->name = outname;
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/* Set archive format and filter according to output file extension.
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* If it fails, set default format. Platform depended function.
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* See supported formats in archive_write_set_format_filter_by_ext.c */
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if (archive_write_set_format_filter_by_ext(a, outname) != ARCHIVE_OK) {
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archive_write_add_filter_gzip(a);
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archive_write_set_format_ustar(a);
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}
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archive_write_open(a, mydata, myopen, mywrite, myclose);
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while (*filename) {
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stat(*filename, &st);
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entry = archive_entry_new();
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archive_entry_copy_stat(entry, &st);
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archive_entry_set_pathname(entry, *filename);
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archive_write_header(a, entry);
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if ((fd = open(*filename, O_RDONLY)) != -1) {
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len = read(fd, buff, sizeof(buff));
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while (len > 0) {
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archive_write_data(a, buff, len);
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len = read(fd, buff, sizeof(buff));
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}
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close(fd);
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}
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archive_entry_free(entry);
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filename++;
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}
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archive_write_free(a);
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}
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int main(int argc, const char **argv)
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{
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const char *outname;
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argv++;
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outname = *argv++;
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write_archive(outname, argv);
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return 0;
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}
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.Ed
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.Sh SEE ALSO
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.Xr tar 1 ,
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.Xr libarchive 3 ,
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.Xr archive_write_set_options 3 ,
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.Xr cpio 5 ,
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.Xr mtree 5 ,
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.Xr tar 5
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.Sh HISTORY
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The
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.Nm libarchive
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library first appeared in
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.Fx 5.3 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm libarchive
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library was written by
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.An Tim Kientzle Aq kientzle@acm.org .
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.Sh BUGS
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There are many peculiar bugs in historic tar implementations that may cause
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certain programs to reject archives written by this library.
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For example, several historic implementations calculated header checksums
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incorrectly and will thus reject valid archives; GNU tar does not fully support
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pax interchange format; some old tar implementations required specific
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field terminations.
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.Pp
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The default pax interchange format eliminates most of the historic
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tar limitations and provides a generic key/value attribute facility
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for vendor-defined extensions.
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One oversight in POSIX is the failure to provide a standard attribute
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for large device numbers.
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This library uses
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.Dq SCHILY.devminor
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and
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.Dq SCHILY.devmajor
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for device numbers that exceed the range supported by the backwards-compatible
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ustar header.
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These keys are compatible with Joerg Schilling's
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.Nm star
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archiver.
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Other implementations may not recognize these keys and will thus be unable
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to correctly restore device nodes with large device numbers from archives
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created by this library.
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