| ARCHIVE_READ(3) | Library Functions Manual | ARCHIVE_READ(3) | 
archive_read —
#include <archive.h>
To read an archive, you must first obtain an initialized struct
    archive object from archive_read_new().
You can then modify this object for the desired operations with
    the various archive_read_set_XXX() and
    archive_read_support_XXX() functions. In particular,
    you will need to invoke appropriate
    archive_read_support_XXX() functions to enable the
    corresponding compression and format support. Note that these latter
    functions perform two distinct operations: they cause the corresponding
    support code to be linked into your program, and they enable the
    corresponding auto-detect code. Unless you have specific constraints, you
    will generally want to invoke
    archive_read_support_filter_all() and
    archive_read_support_format_all() to enable
    auto-detect for all formats and compression types currently supported by the
    library.
Once you have prepared the struct archive object, you call
    archive_read_open() to actually open the archive and
    prepare it for reading. There are several variants of this function; the
    most basic expects you to provide pointers to several functions that can
    provide blocks of bytes from the archive. There are convenience forms that
    allow you to specify a filename, file descriptor, FILE
    * object, or a block of memory from which to read the archive data.
    Note that the core library makes no assumptions about the size of the blocks
    read; callback functions are free to read whatever block size is most
    appropriate for the medium.
Each archive entry consists of a header followed by a certain
    amount of data. You can obtain the next header with
    archive_read_next_header(), which returns a pointer
    to an struct archive_entry structure with information about the current
    archive element. If the entry is a regular file, then the header will be
    followed by the file data. You can use
    archive_read_data() (which works much like the
    read(2) system call) to read
    this data from the archive, or
    archive_read_data_block() which provides a slightly
    more efficient interface. You may prefer to use the higher-level
    archive_read_data_skip(), which reads and discards
    the data for this entry,
    archive_read_data_into_fd(), which copies the data
    to the provided file descriptor, or
    archive_read_extract(), which recreates the
    specified entry on disk and copies data from the archive. In particular,
    note that archive_read_extract() uses the struct
    archive_entry structure that you provide it, which may differ from the entry
    just read from the archive. In particular, many applications will want to
    override the pathname, file permissions, or ownership.
Once you have finished reading data from the archive, you should
    call archive_read_close() to close the archive, then
    call archive_read_free() to release all resources,
    including all memory allocated by the library.
void
list_archive(const char *name)
{
  struct mydata *mydata;
  struct archive *a;
  struct archive_entry *entry;
  mydata = malloc(sizeof(struct mydata));
  a = archive_read_new();
  mydata->name = name;
  archive_read_support_filter_all(a);
  archive_read_support_format_all(a);
  archive_read_open(a, mydata, myopen, myread, myclose);
  while (archive_read_next_header(a, &entry) == ARCHIVE_OK) {
    printf("%s\n",archive_entry_pathname(entry));
    archive_read_data_skip(a);
  }
  archive_read_free(a);
  free(mydata);
}
la_ssize_t
myread(struct archive *a, void *client_data, const void **buff)
{
  struct mydata *mydata = client_data;
  *buff = mydata->buff;
  return (read(mydata->fd, mydata->buff, 10240));
}
int
myopen(struct archive *a, void *client_data)
{
  struct mydata *mydata = client_data;
  mydata->fd = open(mydata->name, O_RDONLY);
  return (mydata->fd >= 0 ? ARCHIVE_OK : ARCHIVE_FATAL);
}
int
myclose(struct archive *a, void *client_data)
{
  struct mydata *mydata = client_data;
  if (mydata->fd > 0)
    close(mydata->fd);
  return (ARCHIVE_OK);
}
libarchive library first appeared in
  FreeBSD 5.3.
libarchive library was written by
  Tim Kientzle ⟨kientzle@acm.org⟩.
| February 2, 2012 | NetBSD 10.0 |