archive_write_open(3) Library Functions Manual archive_write_open(3)
NAME
archive_write_open, archive_write_open2, archive_write_open_fd,
archive_write_open_FILE, archive_write_open_filename,
archive_write_open_memory - functions for creating archives
LIBRARY
Streaming Archive Library (libarchive, -larchive)
SYNOPSIS
#include <archive.h>
int
archive_write_open(struct archive *, void *client_data,
archive_open_callback *, archive_write_callback *,
archive_close_callback *);
int
archive_write_open2(struct archive *, void *client_data,
archive_open_callback *, archive_write_callback *,
archive_close_callback *, archive_free_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);
DESCRIPTION
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. This
does not alter the default archive padding.
archive_write_open2()
Same as archive_write_open() with an additional fourth free
callback. This function should be preferred to
archive_write_open().
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_open2(). 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_open2() 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. This function will
disable padding unless you have specifically set the block size.
More information about the struct archive object and the overall design of
the library can be found in the libarchive(3) overview.
Note that the convenience forms above vary in how they block the output.
See archive_write_blocksize(3) if you need to control the block size used
for writes or the end-of-file padding behavior.
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_open2():
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. Please note that if open fails,
close is not called and resources must be freed inside the open callback or
with the free callback.
typedef la_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. If the open callback fails, the close callback is not invoked.
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.
typedef int archive_free_callback(struct archive *, void
*client_data)
The free callback is always invoked on archive_free. The return code of
this callback is not processed.
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(),
archive_write_finish(), 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().
RETURN VALUES
These functions return ARCHIVE_OK on success, or ARCHIVE_FATAL.
ERRORS
Detailed error codes and textual descriptions are available from the
archive_errno() and archive_error_string() functions.
SEE ALSO
tar(1), archive_write(3), archive_write_blocksize(3),
archive_write_filter(3), archive_write_format(3), archive_write_new(3),
archive_write_set_options(3), libarchive(3), cpio(5), mtree(5), tar(5)
macOS 12.6 November 12, 2020 macOS 12.6
libarchive 3.6.2 - Generated Wed Dec 14 08:11:23 CST 2022