409 lines
14 KiB
Groff
409 lines
14 KiB
Groff
.\" Copyright (c) 2003-2005 Tim Kientzle
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd January 8, 2005
|
|
.Dt archive_write 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm archive_write_new ,
|
|
.Nm archive_write_set_format_cpio ,
|
|
.Nm archive_write_set_format_pax ,
|
|
.Nm archive_write_set_format_pax_restricted ,
|
|
.Nm archive_write_set_format_shar ,
|
|
.Nm archive_write_set_format_shar_binary ,
|
|
.Nm archive_write_set_format_ustar ,
|
|
.Nm archive_write_set_bytes_per_block ,
|
|
.Nm archive_write_set_bytes_in_last_block ,
|
|
.Nm archive_write_set_compressor_gzip ,
|
|
.Nm archive_write_set_compressor_bzip2 ,
|
|
.Nm archive_write_open ,
|
|
.Nm archive_write_open_fd ,
|
|
.Nm archive_write_open_file ,
|
|
.Nm archive_write_prepare ,
|
|
.Nm archive_write_header ,
|
|
.Nm archive_write_data ,
|
|
.Nm archive_write_close ,
|
|
.Nm archive_write_finish
|
|
.Nd functions for creating archives
|
|
.Sh SYNOPSIS
|
|
.In archive.h
|
|
.Ft struct archive *
|
|
.Fn archive_write_new "void"
|
|
.Ft int
|
|
.Fn archive_write_set_bytes_per_block "archive *" "int bytes_per_block"
|
|
.Ft int
|
|
.Fn archive_write_set_bytes_in_last_block "archive *" "int"
|
|
.Ft int
|
|
.Fn archive_write_set_compressor_gzip "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_compressor_bzip2 "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_format_cpio "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_format_pax "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_format_pax_restricted "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_format_shar "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_format_shar_binary "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_set_format_ustar "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_open "struct archive *" "void *client_data" "archive_open_archive_callback *" "archive_write_archive_callback *" "archive_close_archive_callback *"
|
|
.Ft int
|
|
.Fn archive_write_open_fd "struct archive *" "int fd"
|
|
.Ft int
|
|
.Fn archive_write_open_file "struct archive *" "const char *filename"
|
|
.Ft int
|
|
.Fn archive_write_header "struct archive *"
|
|
.Ft int
|
|
.Fn archive_write_data "struct archive *" "const void *" "size_t"
|
|
.Ft int
|
|
.Fn archive_write_close "struct archive *"
|
|
.Ft void
|
|
.Fn archive_write_finish "struct archive *"
|
|
.Sh DESCRIPTION
|
|
These functions provide a complete API for creating streaming
|
|
archive files.
|
|
The general process is to first create the
|
|
.Tn 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:
|
|
.Bl -tag -width indent
|
|
.It Fn archive_write_new
|
|
Allocates and initializes a
|
|
.Tn struct archive
|
|
object suitable for writing a tar archive.
|
|
.It Fn 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.
|
|
.It Fn 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
|
|
.Fn archive_write_open_file
|
|
will set this based on the file type).
|
|
Unlike the other
|
|
.Dq set
|
|
functions, this function can be called after the archive is opened.
|
|
.It Fn archive_write_set_format_cpio , Fn archive_write_set_format_pax , Fn archive_write_set_format_pax_restricted , Fn archive_write_set_format_shar , Fn archive_write_set_format_shar_binary , Fn 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
|
|
.Dq pax interchange
|
|
format archives,
|
|
traditional
|
|
.Dq shar
|
|
archives,
|
|
enhanced
|
|
.Dq binary
|
|
shar archives that store a variety of file attributes and handle binary files,
|
|
and
|
|
POSIX-standard
|
|
.Dq 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.
|
|
.Dq 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.
|
|
.It Fn archive_write_set_compression_gzip , Fn archive_write_set_compression_bzip2
|
|
The resulting archive will be compressed as specified.
|
|
Note that the compressed output is always properly blocked.
|
|
.It Fn 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.
|
|
In order to support external compression programs, the compression
|
|
is permitted to fork and invoke the callbacks from a separate process.
|
|
In particular, clients should not assume that they can communicate
|
|
between the callbacks and the mainline code using shared variables.
|
|
(The standard gzip, bzip2, and "none" compression methods do not fork.)
|
|
.It Fn archive_write_open_fd
|
|
A convenience form of
|
|
.Fn archive_write_open
|
|
that accepts a file descriptor.
|
|
.It Fn archive_write_open_file
|
|
A convenience form of
|
|
.Fn archive_write_open
|
|
that accepts a filename.
|
|
A NULL argument indicates that the output should be written to standard output;
|
|
an argument of
|
|
.Dq -
|
|
will open a file with that name.
|
|
If you have not invoked
|
|
.Fn archive_write_set_bytes_in_last_block ,
|
|
then
|
|
.Fn archive_write_open_file
|
|
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
|
|
.Fn archive_write_set_bytes_in_last_block
|
|
either before or after calling
|
|
.Fn archive_write_open .
|
|
.It Fn archive_write_header
|
|
Build and write a header using the data in the provided
|
|
.Tn struct archive_entry
|
|
structure.
|
|
.It Fn archive_write_data
|
|
Write data corresponding to the header just written.
|
|
Returns number of bytes written or -1 on error.
|
|
.It Fn archive_write_close
|
|
Complete the archive and invoke the close callback.
|
|
.It Fn archive_write_finish
|
|
Invokes
|
|
.Fn archive_write_close
|
|
if it was not invoked manually, then release all resources.
|
|
.El
|
|
More information about the
|
|
.Va struct archive
|
|
object and the overall design of the library can be found in the
|
|
.Xr libarchive 3
|
|
overview.
|
|
.Sh IMPLEMENTATION
|
|
Compression support is built-in to libarchive, which uses zlib and bzlib
|
|
to handle gzip and bzip2 compression, respectively.
|
|
.Sh 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
|
|
.Fn archive_write_open :
|
|
.Bl -item -offset indent
|
|
.It
|
|
.Ft typedef int
|
|
.Fn archive_open_archive_callback "struct archive *" "void *client_data"
|
|
.El
|
|
.Pp
|
|
The open callback is invoked by
|
|
.Fn archive_write_open .
|
|
It should return
|
|
.Cm ARCHIVE_OK
|
|
if the underlying file or data source is successfully
|
|
opened.
|
|
If the open fails, it should call
|
|
.Fn archive_set_error
|
|
to register an error code and message and return
|
|
.Cm ARCHIVE_FATAL .
|
|
.Bl -item -offset indent
|
|
.It
|
|
.Ft typedef ssize_t
|
|
.Fn archive_write_archive_callback "struct archive *" "void *client_data" "void *buffer" "size_t length"
|
|
.El
|
|
.Pp
|
|
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
|
|
.Xr 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
|
|
.Fn archive_set_error
|
|
to register an error code and message and return -1.
|
|
.Bl -item -offset indent
|
|
.It
|
|
.Ft typedef int
|
|
.Fn archive_close_archive_callback "struct archive *" "void *client_data"
|
|
.El
|
|
.Pp
|
|
The close callback is invoked by archive_close when
|
|
the archive processing is complete.
|
|
The callback should return
|
|
.Cm ARCHIVE_OK
|
|
on success.
|
|
On failure, the callback should invoke
|
|
.Fn archive_set_error
|
|
to register an error code and message and
|
|
regurn
|
|
.Cm ARCHIVE_FATAL.
|
|
.Sh EXAMPLE
|
|
The following sketch illustrates basic usage of the library.
|
|
In this example,
|
|
the callback functions are simply wrappers around the standard
|
|
.Xr open 2 ,
|
|
.Xr write 2 ,
|
|
and
|
|
.Xr close 2
|
|
system calls.
|
|
.Bd -literal -offset indent
|
|
void
|
|
write_archive(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;
|
|
|
|
a = archive_write_new();
|
|
mydata->name = name;
|
|
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
|
|
myopen(struct archive *a, void *client_data)
|
|
{
|
|
struct mydata *mydata = client_data;
|
|
|
|
mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644);
|
|
return (mydata->fd >= 0);
|
|
}
|
|
|
|
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);
|
|
}
|
|
.Ed
|
|
.Sh RETURN VALUES
|
|
Most functions return zero on success, non-zero on error.
|
|
The
|
|
.Fn archive_errno
|
|
and
|
|
.Fn archive_error_string
|
|
functions can be used to retrieve an appropriate error code and a
|
|
textual error message.
|
|
.Pp
|
|
.Fn archive_write_new
|
|
returns a pointer to a newly-allocated
|
|
.Tn struct archive
|
|
object.
|
|
.Pp
|
|
.Fn archive_write_data
|
|
returns a count of the number of bytes actually written.
|
|
On error, -1 is returned and the
|
|
.Fn archive_errno
|
|
and
|
|
.Fn 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
|
|
.Fn archive_write_header ,
|
|
.Fn archive_write_data ,
|
|
or
|
|
.Fn archive_write_close .
|
|
The client callback can call
|
|
.Fn archive_set_error
|
|
to provide values that can then be retrieved by
|
|
.Fn archive_errno
|
|
and
|
|
.Fn archive_error_string .
|
|
.Sh SEE ALSO
|
|
.Xr tar 1 ,
|
|
.Xr libarchive 3 ,
|
|
.Xr tar 5
|
|
.Sh HISTORY
|
|
The
|
|
.Nm libarchive
|
|
library first appeared in
|
|
.Fx 5.3 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Nm libarchive
|
|
library was written by
|
|
.An Tim Kientzle Aq kientzle@acm.org .
|
|
.Sh 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.
|
|
.Pp
|
|
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
|
|
.Dq SCHILY.devminor
|
|
and
|
|
.Dq SCHILY.devmajor
|
|
for device numbers that exceed the range supported by the backwards-compatible
|
|
ustar header.
|
|
These keys are compatible with Joerg Schilling's
|
|
.Nm star
|
|
archiver.
|
|
Other implementations may not recognize these keys and will thus be unable
|
|
to correctly restore large device numbers archived by this library.
|