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/*
* This file is in the public domain.
* Use it as you wish.
*/
/*
* This is a compact tar extraction program whose primary goal is
* small size. Statically linked, it can be under 64k, depending on
* how cleanly factored your system libraries are. Note that this
* uses the standard libarchive, without any special recompilation.
* The only functional concession is that this program uses the
* uid/gid from the archive instead of doing uname/gname lookups.
* (Call archive_write_disk_set_standard_lookup() to enable
* uname/gname lookups, but be aware that this can add 500k or more to
* a static executable, depending on the system libraries.)
*
* To build:
* gcc -static -Wall -o untar untar.c -larchive
* strip untar
*
* For fun, statically compile the following simple hello.c program
* and compare the size. (On my system, the result is 89k, untar is
* 69k.)
*
* #include <stdio.h>
* int main(int argc, char **argv) {
* printf("hello, world\n");
* return(0);
* }
*/
#include <sys/types.h>
__FBSDID("$FreeBSD$");
#include <sys/stat.h>
#include <archive.h>
#include <archive_entry.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static void errmsg(const char *);
static void extract(const char *filename, int do_extract, int flags);
static int copy_data(struct archive *, struct archive *);
static void msg(const char *);
static void usage(void);
static int verbose = 0;
int
main(int argc, const char **argv)
{
const char *filename = NULL;
int compress, flags, mode, opt;
(void)argc;
mode = 'x';
verbose = 0;
compress = '\0';
flags = ARCHIVE_EXTRACT_TIME;
/* Among other sins, getopt(3) pulls in printf(3). */
while (*++argv != NULL && **argv == '-') {
const char *p = *argv + 1;
while ((opt = *p++) != '\0') {
switch (opt) {
case 'f':
if (*p != '\0')
filename = p;
else
filename = *++argv;
p += strlen(p);
break;
case 'p':
flags |= ARCHIVE_EXTRACT_PERM;
flags |= ARCHIVE_EXTRACT_ACL;
flags |= ARCHIVE_EXTRACT_FFLAGS;
break;
case 't':
mode = opt;
break;
case 'v':
verbose++;
break;
case 'x':
mode = opt;
break;
default:
usage();
}
}
}
switch (mode) {
case 't':
extract(filename, 0, flags);
break;
case 'x':
extract(filename, 1, flags);
break;
}
return (0);
}
static void
extract(const char *filename, int do_extract, int flags)
{
struct archive *a;
struct archive *ext;
struct archive_entry *entry;
int r;
a = archive_read_new();
ext = archive_write_disk_new();
archive_write_disk_set_options(ext, flags);
/*
* Note: archive_write_disk_set_standard_lookup() is useful
* here, but it requires library routines that can add 500k or
* more to a static executable.
*/
archive_read_support_format_tar(a);
/*
* On my system, enabling other archive formats adds 20k-30k
* each. Enabling gzip decompression adds about 20k.
* Enabling bzip2 is more expensive because the libbz2 library
* isn't very well factored.
*/
if (filename != NULL && strcmp(filename, "-") == 0)
filename = NULL;
if ((r = archive_read_open_file(a, filename, 10240))) {
errmsg(archive_error_string(a));
errmsg("\n");
exit(r);
}
for (;;) {
r = archive_read_next_header(a, &entry);
if (r == ARCHIVE_EOF)
break;
if (r != ARCHIVE_OK) {
errmsg(archive_error_string(a));
errmsg("\n");
exit(1);
}
if (verbose && do_extract)
msg("x ");
if (verbose || !do_extract)
msg(archive_entry_pathname(entry));
if (do_extract) {
r = archive_write_header(ext, entry);
if (r != ARCHIVE_OK)
errmsg(archive_error_string(a));
else
copy_data(a, ext);
}
if (verbose || !do_extract)
msg("\n");
}
archive_read_close(a);
archive_read_finish(a);
exit(0);
}
static int
copy_data(struct archive *ar, struct archive *aw)
{
int r;
const void *buff;
size_t size;
off_t offset;
for (;;) {
r = archive_read_data_block(ar, &buff, &size, &offset);
if (r == ARCHIVE_EOF) {
errmsg(archive_error_string(ar));
return (ARCHIVE_OK);
}
if (r != ARCHIVE_OK)
return (r);
r = archive_write_data_block(aw, buff, size, offset);
if (r != ARCHIVE_OK) {
errmsg(archive_error_string(ar));
return (r);
}
}
}
static void
msg(const char *m)
{
write(1, m, strlen(m));
}
static void
errmsg(const char *m)
{
write(2, m, strlen(m));
}
static void
usage(void)
{
const char *m = "Usage: untar [-tvx] [-f file] [file]\n";
errmsg(m);
exit(1);
}
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