Promote tar.

There's probably more to do, but it seems usable at this point.

1 files changed, 814 insertions, 0 deletions

diff --git a/toys/posix/tar.c b/toys/posix/tar.c
new file mode 100644
index 00000000..cfeedcba
--- /dev/null
+++ b/toys/posix/tar.c
@@ -0,0 +1,814 @@
+/* tar.c - create/extract archives
+ *
+ * Copyright 2014 Ashwini Kumar <ak.ashwini81@gmail.com>
+ *
+ * For the command, see
+ *   http://pubs.opengroup.org/onlinepubs/007908799/xcu/tar.html
+ * For the modern file format, see
+ *   http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_06
+ *   https://en.wikipedia.org/wiki/Tar_(computing)#File_format
+ *   https://www.gnu.org/software/tar/manual/html_node/Tar-Internals.html
+ *
+ * For writing to external program
+ * http://www.gnu.org/software/tar/manual/html_node/Writing-to-an-External-Program.html
+ *
+ * Toybox will never implement the "pax" command as a matter of policy.
+ *
+ * Why --exclude pattern but no --include? tar cvzf a.tgz dir --include '*.txt'
+ * Extract into dir same as filename, --restrict? "Tarball is splodey"
+ *
+
+USE_TAR(NEWTOY(tar, "&(restrict)(full-time)(no-recursion)(numeric-owner)(no-same-permissions)(overwrite)(exclude)*(mtime):(group):(owner):(to-command):o(no-same-owner)p(same-permissions)k(keep-old)c(create)|h(dereference)x(extract)|t(list)|v(verbose)J(xz)j(bzip2)z(gzip)O(to-stdout)m(touch)X(exclude-from)*T(files-from)*C(directory):f(file):a[!txc][!jzJa]", TOYFLAG_USR|TOYFLAG_BIN))
+
+config TAR
+  bool "tar"
+  default y
+  help
+    usage: tar [-cxtfvohmjkO] [-XT FILE] [-f TARFILE] [-C DIR]
+
+    Create, extract, or list files in a .tar (or compressed t?z) file. 
+
+    Options:
+    c  Create                x  Extract               t  Test
+    f  Name of TARFILE       C  Change to DIR first   v  Verbose: show filenames
+    o  Ignore owner          h  Follow symlinks       m  Ignore mtime
+    j  bzip2 compression     z  gzip compression
+    O  Extract to stdout     X  exclude names in FILE T  include names in FILE
+    --exclude=FILE File pattern(s) to exclude
+    --restrict  All archive contents must extract under a single subdirctory.
+*/
+
+#define FOR_tar
+#include "toys.h"
+
+GLOBALS(
+  char *f, *C;
+  struct arg_list *T, *X;
+  char *to_command, *owner, *group, *mtime;
+  struct arg_list *exclude;
+
+  struct double_list *incl, *excl, *seen;
+  struct string_list *dirs;
+  char *cwd;
+  int fd, ouid, ggid, hlc, warn, adev, aino;
+  time_t mtt;
+
+  // hardlinks seen so far (hlc many)
+  struct {
+    char *arg;
+    ino_t ino;
+    dev_t dev;
+  } *hlx;
+
+  // Parsed information about a tar header.
+  struct tar_header {
+    char *name, *link_target, *uname, *gname;
+    long long size;
+    uid_t uid;
+    gid_t gid;
+    mode_t mode;
+    time_t mtime;
+    dev_t device;
+  } hdr;
+)
+
+struct tar_hdr {
+  char name[100], mode[8], uid[8], gid[8],size[12], mtime[12], chksum[8],
+       type, link[100], magic[8], uname[32], gname[32], major[8], minor[8],
+       prefix[155], padd[12];
+};
+
+// convert from int to octal (or base-256)
+static void itoo(char *str, int len, unsigned long long val)
+{
+  // Do we need binary encoding?
+  if (!(val>>(3*(len-1)))) sprintf(str, "%0*llo", len-1, val);
+  else {
+    *str = 128;
+    while (--len) *++str = val>>(3*len);
+  }
+}
+#define ITOO(x, y) itoo(x, sizeof(x), y)
+
+// convert octal (or base-256) to int
+static unsigned long long otoi(char *str, unsigned len)
+{
+  unsigned long long val = 0;
+
+  // When tar value too big or octal, use binary encoding with high bit set
+  if (128&*str) while (--len) val = (val<<8)+*++str;
+  else {
+    while (len && *str>='0' && *str<='7') val = val*8+*str++-'0', len--;
+    if (len && *str && *str != ' ') error_exit("bad header");
+  }
+
+  return val;
+}
+#define OTOI(x) otoi(x, sizeof(x))
+
+// Calculate packet checksum, with cksum field treated as 8 spaces
+static unsigned cksum(void *data)
+{
+  unsigned i, cksum = 8*' ';
+
+  for (i = 0; i<500; i += (i==147) ? 9 : 1) cksum += ((char *)data)[i];
+
+  return cksum;
+}
+
+static void write_longname(char *name, char type)
+{
+  struct tar_hdr tmp;
+  int sz = strlen(name) +1;
+
+  memset(&tmp, 0, sizeof(tmp));
+  strcpy(tmp.name, "././@LongLink");
+  ITOO(tmp.uid, 0);
+  ITOO(tmp.gid, 0);
+  ITOO(tmp.size, sz);
+  ITOO(tmp.mtime, 0);
+  tmp.type = type;
+  strcpy(tmp.magic, "ustar  ");
+
+  // Historical nonsense to match other implementations. Never used.
+  ITOO(tmp.mode, 0644);
+  strcpy(tmp.uname, "root");
+  strcpy(tmp.gname, "root");
+
+  // Calculate checksum. Since 512*255 = 0377000 in octal, this can never
+  // use more than 6 digits. The last byte is ' ' or historical reasons.
+  itoo(tmp.chksum, sizeof(tmp.chksum)-1, cksum(&tmp));
+  tmp.chksum[7] = ' ';
+
+  // write header and name, padded with NUL to block size
+  xwrite(TT.fd, &tmp, 512);
+  xwrite(TT.fd, name, sz);
+  if (sz%512) xwrite(TT.fd, toybuf, 512-(sz%512));
+}
+
+static struct double_list *filter(struct double_list *lst, char *name)
+{
+  struct double_list *end = lst;
+
+  if (lst)
+    // constant is FNM_LEADING_DIR
+    do if (!fnmatch(lst->data, name, 1<<3)) return lst;
+    while (end != (lst = lst->next));
+
+  return 0;
+}
+
+static void skippy(long long len)
+{
+  if (lskip(TT.fd, len)) perror_exit("EOF");
+}
+
+// allocate and read data from TT.fd
+static void alloread(void *buf, int len)
+{
+  // actually void **, but automatic typecasting doesn't work with void ** :(
+  void **b = buf;
+
+  free(*b);
+  *b = xmalloc(len+1);
+  xreadall(TT.fd, *b, len);
+  b[len] = 0;
+}
+
+// callback from dirtree to create archive
+static int add_to_tar(struct dirtree *node)
+{
+  struct stat *st = &(node->st);
+  struct tar_hdr hdr;
+  struct passwd *pw = pw;
+  struct group *gr = gr;
+  int i, fd =-1;
+  char *c, *p, *name, *lnk = lnk, *hname;
+
+  if (!dirtree_notdotdot(node)) return 0;
+  if (TT.adev == st->st_dev && TT.aino == st->st_ino) {
+    error_msg("'%s' file is the archive; not dumped", node->name);
+    return 0;
+  }
+
+  i = 1;
+  name = dirtree_path(node, &i);
+
+  // exclusion defaults to --no-anchored and --wildcards-match-slash
+  for (p = name; *p;) {
+    if (filter(TT.excl, p)) goto done;
+    while (*p && *p!='/') p++;
+    while (*p=='/') p++;
+  }
+
+  // Consume the 1 extra byte alocated in dirtree_path()
+  if (S_ISDIR(st->st_mode) && name[i-1] != '/') strcat(name, "/");
+
+  // remove leading / and any .. entries from saved name
+  for (hname = name; *hname == '/'; hname++);
+  for (c = hname;;) {
+    if (!(c = strstr(c, ".."))) break;
+    if (c == hname || c[-1] == '/') {
+      if (!c[2]) goto done;
+      if (c[2]=='/') c = hname = c+3;
+    } else c+= 2;
+  }
+  if (!*hname) goto done;
+
+  if (TT.warn && hname != name) {
+    fprintf(stderr, "removing leading '%.*s' from member names\n",
+           (int)(hname-name), name);
+    TT.warn = 0;
+  }
+
+  if (TT.owner) st->st_uid = TT.ouid;
+  if (TT.group) st->st_gid = TT.ggid;
+  if (TT.mtime) st->st_mtime = TT.mtt;
+
+  memset(&hdr, 0, sizeof(hdr));
+  strncpy(hdr.name, hname, sizeof(hdr.name));
+  ITOO(hdr.mode, st->st_mode &07777);
+  ITOO(hdr.uid, st->st_uid);
+  ITOO(hdr.gid, st->st_gid);
+  ITOO(hdr.size, 0); //set size later
+  ITOO(hdr.mtime, st->st_mtime);
+  strcpy(hdr.magic, "ustar  ");
+
+  // Hard link or symlink? i=0 neither, i=1 hardlink, i=2 symlink
+
+  // Are there hardlinks to a non-directory entry?
+  if (st->st_nlink>1 && !S_ISDIR(st->st_mode)) {
+    // Have we seen this dev&ino before?
+    for (i = 0; i<TT.hlc; i++) {
+      if (st->st_ino == TT.hlx[i].ino && st->st_dev == TT.hlx[i].dev)
+        break;
+    }
+    if (i != TT.hlc) {
+      lnk = TT.hlx[i].arg;
+      i = 1;
+    } else {
+      // first time we've seen it. Store as normal file, but remember it.
+      if (!(TT.hlc&255)) TT.hlx = xrealloc(TT.hlx, TT.hlc+256);
+      TT.hlx[TT.hlc].arg = xstrdup(hname);
+      TT.hlx[TT.hlc].ino = st->st_ino;
+      TT.hlx[TT.hlc].dev = st->st_dev;
+      TT.hlc++;
+      i = 0;
+    }
+  } else i = 0;
+
+  // !i because hardlink to a symlink is a thing.
+  if (!i && S_ISLNK(st->st_mode)) {
+    i = 2;
+    lnk = xreadlink(name);
+  }
+
+  // Handle file types
+  if (i) {
+    hdr.type = '0'+i;
+    if (i==2 && !(lnk = xreadlink(name))) {
+      perror_msg("readlink");
+      goto done;
+    }
+    if (strlen(lnk) > sizeof(hdr.link)) write_longname(lnk, 'K');
+    strncpy(hdr.link, lnk, sizeof(hdr.link));
+    if (i) free(lnk);
+  } else if (S_ISREG(st->st_mode)) {
+    hdr.type = '0';
+    ITOO(hdr.size, st->st_size);
+  } else if (S_ISDIR(st->st_mode)) hdr.type = '5';
+  else if (S_ISFIFO(st->st_mode)) hdr.type = '6';
+  else if (S_ISBLK(st->st_mode) || S_ISCHR(st->st_mode)) {
+    hdr.type = (S_ISCHR(st->st_mode))?'3':'4';
+    ITOO(hdr.major, dev_major(st->st_rdev));
+    ITOO(hdr.minor, dev_minor(st->st_rdev));
+  } else {
+    error_msg("unknown file type '%o'", st->st_mode & S_IFMT);
+    goto done;
+  }
+
+  if (strlen(hname) > sizeof(hdr.name)) write_longname(hname, 'L');
+
+  if (!FLAG(numeric_owner)) {
+    if (TT.owner || (pw = bufgetpwuid(st->st_uid)))
+      strncpy(hdr.uname, TT.owner ? TT.owner : pw->pw_name, sizeof(hdr.uname));
+    if (TT.group || (gr = bufgetgrgid(st->st_gid)))
+      strncpy(hdr.gname, TT.group ? TT.group : gr->gr_name, sizeof(hdr.gname));
+  }
+
+  itoo(hdr.chksum, sizeof(hdr.chksum)-1, cksum(&hdr));
+  hdr.chksum[7] = ' ';
+
+  if (FLAG(v)) printf("%s\n", hname);
+
+  // Write header and data to archive
+  xwrite(TT.fd, &hdr, 512);
+  if (hdr.type == '0') {
+    if ((fd = open(name, O_RDONLY)) < 0) perror_msg("can't open '%s'", name);
+    else {
+      xsendfile_pad(fd, TT.fd, st->st_size);
+      if (st->st_size%512) writeall(TT.fd, toybuf, (512-(st->st_size%512)));
+      close(fd);
+    }
+  }
+done:
+  free(name);
+
+  return (DIRTREE_RECURSE|(FLAG(h)?DIRTREE_SYMFOLLOW:0))*!FLAG(no_recursion);
+}
+
+static void wsettime(char *s, long long sec)
+{
+  struct timespec times[2] = {{sec, 0},{sec, 0}};
+
+  if (utimensat(AT_FDCWD, s, times, AT_SYMLINK_NOFOLLOW))
+    perror_msg("settime %lld %s", sec, s);
+}
+
+// Do pending directory utimes(), NULL to flush all.
+static int dirflush(char *name)
+{
+  char *s = 0, *ss;
+
+  // Barf if name not in TT.cwd
+  if (name) {
+    ss = s = xabspath(name, -1);
+    if (TT.cwd[1] && (!strstart(&ss, TT.cwd) || *ss!='/')) {
+      error_msg("'%s' not under '%s'", name, TT.cwd);
+      free(s);
+
+      return 1;
+    }
+
+    if (FLAG(restrict)) {
+      free(TT.cwd);
+      TT.cwd = strdup(s);
+      toys.optflags ^= FLAG_restrict;
+    }
+  }
+
+  // Set deferred utimes() for directories this file isn't under.
+  // (Files must be depth-first ordered in tarball for this to matter.)
+  while (TT.dirs) {
+
+    // If next file is under (or equal to) this dir, keep waiting
+    if (name && strstart(&ss, ss = s) && (!*ss || *ss=='/')) break;
+
+    wsettime(TT.dirs->str+sizeof(long long), *(long long *)TT.dirs->str);
+    free(llist_pop(&TT.dirs));
+  }
+  free(s);
+
+  // name was under TT.cwd
+  return 0;
+}
+
+static void extract_to_disk(void)
+{
+  char *name = TT.hdr.name;
+  int ala = TT.hdr.mode;
+
+  if (dirflush(name)) {
+    if (S_ISREG(ala) && !TT.hdr.link_target) skippy(TT.hdr.size);
+ 
+    return;
+  }
+
+  // create path before file if necessary
+  if (strrchr(name, '/') && mkpath(name) && errno !=EEXIST)
+      return perror_msg(":%s: can't mkdir", name);
+
+  // remove old file, if exists
+  if (!FLAG(k) && !S_ISDIR(ala) && unlink(name) && errno!=ENOENT)
+    return perror_msg("can't remove: %s", name);
+
+  if (S_ISREG(ala)) {
+    // hardlink?
+    if (TT.hdr.link_target) {
+      if (link(TT.hdr.link_target, name))
+        return perror_msg("can't link '%s' -> '%s'", name, TT.hdr.link_target);
+    // write contents
+    } else {
+      int fd = xcreate(name, O_WRONLY|O_CREAT|(FLAG(overwrite)?O_TRUNC:O_EXCL),
+        WARN_ONLY|(ala & 07777));
+      if (fd != -1) {
+        xsendfile_len(TT.fd, fd, TT.hdr.size);
+        close(fd);
+      }
+    }
+  } else if (S_ISDIR(ala)) {
+    if ((mkdir(name, 0700) == -1) && errno != EEXIST)
+      return perror_msg("%s: can't create", TT.hdr.name);
+  } else if (S_ISLNK(ala)) {
+    if (symlink(TT.hdr.link_target, TT.hdr.name))
+      return perror_msg("can't link '%s' -> '%s'", name, TT.hdr.link_target);
+  } else if (mknod(name, ala, TT.hdr.device))
+    return perror_msg("can't create '%s'", name);
+
+  // Set ownership
+  if (!FLAG(o) && !geteuid()) {
+    int u = TT.hdr.uid, g = TT.hdr.gid;
+
+    if (TT.owner) TT.hdr.uid = TT.ouid;
+    else if (!FLAG(numeric_owner) && *TT.hdr.uname) {
+      struct passwd *pw = getpwnam(TT.hdr.uname);
+      if (pw && (TT.owner || !FLAG(numeric_owner))) TT.hdr.uid = pw->pw_uid;
+    }
+
+    if (TT.group) TT.hdr.gid = TT.ggid;
+    else if (!FLAG(numeric_owner) && *TT.hdr.uname) {
+      struct group *gr = getgrnam(TT.hdr.gname);
+      if (gr) TT.hdr.gid = gr->gr_gid;
+    }
+
+    if (lchown(name, u, g)) perror_msg("chown %d:%d '%s'", u, g, name);;
+  }
+
+  if (!S_ISLNK(ala)) chmod(TT.hdr.name, FLAG(p) ? ala : ala&0777);
+
+  // Apply mtime.
+  if (!FLAG(m)) {
+    if (S_ISDIR(ala)) {
+      struct string_list *sl;
+
+      // Writing files into a directory changes directory timestamps, so
+      // defer mtime updates until contents written.
+
+      sl = xmalloc(sizeof(struct string_list)+sizeof(long long)+strlen(name)+1);
+      *(long long *)sl->str = TT.hdr.mtime;
+      strcpy(sl->str+sizeof(long long), name);
+      sl->next = TT.dirs;
+      TT.dirs = sl;
+    } else wsettime(TT.hdr.name, TT.hdr.mtime);
+  }
+}
+
+static void unpack_tar(struct tar_hdr *first)
+{
+  struct double_list *walk, *delete;
+  struct tar_hdr tar;
+  int i, and = 0;
+  unsigned maj, min;
+  char *s;
+
+  for (;;) {
+    if (first) {
+      memcpy(&tar, first, i = 512);
+      first = 0;
+    } else {
+      // align to next block and read it
+      if (TT.hdr.size%512) skippy(512-TT.hdr.size%512);
+      i = readall(TT.fd, &tar, 512);
+    }
+
+    if (i && i!=512) error_exit("short header");
+
+    // Two consecutive empty headers ends tar even if there's more data
+    if (!i || !*tar.name) {
+      if (!i || and++) return;
+      TT.hdr.size = 0;
+      continue;
+    }
+    // ensure null temination even of pathological packets
+    tar.padd[0] = and = 0;
+
+    // Is this a valid Unix Standard TAR header?
+    if (memcmp(tar.magic, "ustar", 5)) error_exit("bad header");
+    if (cksum(&tar) != OTOI(tar.chksum)) error_exit("bad cksum");
+    TT.hdr.size = OTOI(tar.size);
+
+    // If this header isn't writing something to the filesystem
+    if (tar.type<'0' || tar.type>'7') {
+
+      // Long name extension header?
+      if (tar.type == 'K') alloread(&TT.hdr.link_target, TT.hdr.size);
+      else if (tar.type == 'L') alloread(&TT.hdr.name, TT.hdr.size);
+      else if (tar.type == 'x') {
+        char *p, *buf = 0;
+        int i, len, n;
+
+        // Posix extended record "LEN NAME=VALUE\n" format
+        alloread(&buf, TT.hdr.size);
+        for (p = buf; (p-buf)<TT.hdr.size; p += len) {
+          i = sscanf(p, "%u path=%n", &len, &n);
+          if (i<1 || len<4 || len>TT.hdr.size) {
+            error_msg("bad header");
+            break;
+          }
+          p[len-1] = 0;
+          if (i == 2) {
+            TT.hdr.name = xstrdup(p+n);
+            break;
+          }
+        }
+        free(buf);
+
+      // Ignore everything else.
+      } else skippy(TT.hdr.size);
+
+      continue;
+    }
+
+    // At this point, we have something to output. Convert metadata.
+    TT.hdr.mode = OTOI(tar.mode);
+    TT.hdr.mode |= (char []){8,8,10,2,6,4,1,8}[tar.type-'0']<<12;
+    TT.hdr.uid = OTOI(tar.uid);
+    TT.hdr.gid = OTOI(tar.gid);
+    TT.hdr.mtime = OTOI(tar.mtime);
+    maj = OTOI(tar.major);
+    min = OTOI(tar.minor);
+    TT.hdr.device = dev_makedev(maj, min);
+
+    TT.hdr.uname = xstrndup(TT.owner ? TT.owner : tar.uname, sizeof(tar.uname));
+    TT.hdr.gname = xstrndup(TT.group ? TT.group : tar.gname, sizeof(tar.gname));
+
+    if (TT.owner) TT.hdr.uid = TT.ouid;
+    else if (!FLAG(numeric_owner)) {
+      struct passwd *pw = getpwnam(TT.hdr.uname);
+      if (pw && (TT.owner || !FLAG(numeric_owner))) TT.hdr.uid = pw->pw_uid;
+    }
+
+    if (TT.group) TT.hdr.gid = TT.ggid;
+    else if (!FLAG(numeric_owner)) {
+      struct group *gr = getgrnam(TT.hdr.gname);
+      if (gr) TT.hdr.gid = gr->gr_gid;
+    }
+
+    if (!TT.hdr.link_target && *tar.link)
+      TT.hdr.link_target = xstrndup(tar.link, sizeof(tar.link));
+    if (!TT.hdr.name) {
+      // Glue prefix and name fields together with / if necessary
+      i = strnlen(tar.prefix, sizeof(tar.prefix));
+      TT.hdr.name = xmprintf("%.*s%s%.*s", i, tar.prefix,
+        (i && tar.prefix[i-1] != '/') ? "/" : "",
+        (int)sizeof(tar.name), tar.name);
+    }
+
+    // Old broken tar recorded dir as "file with trailing slash"
+    if (S_ISREG(TT.hdr.mode) && (s = strend(TT.hdr.name, "/"))) {
+      *s = 0;
+      TT.hdr.mode = (TT.hdr.mode & ~S_IFMT) | S_IFDIR;
+    }
+
+    // Non-regular files don't have contents stored in archive.
+    if ((TT.hdr.link_target && *TT.hdr.link_target) || !S_ISREG(TT.hdr.mode))
+      TT.hdr.size = 0;
+
+    // Files are seen even if excluded, so check them here.
+    // TT.seen points to first seen entry in TT.incl, or NULL if none yet.
+
+    if ((delete = filter(TT.incl, TT.hdr.name)) && TT.incl != TT.seen) {
+      if (!TT.seen) TT.seen = delete;
+
+      // Move seen entry to end of list.
+      if (TT.incl == delete) TT.incl = TT.incl->next;
+      else for (walk = TT.incl; walk != TT.seen; walk = walk->next) {
+        if (walk == delete) {
+          dlist_pop(&walk);
+          dlist_add_nomalloc(&TT.incl, delete);
+        }
+      }
+    }
+
+    // Skip excluded files
+    if (filter(TT.excl, TT.hdr.name) || (TT.incl && !delete))
+      skippy(TT.hdr.size);
+    else if (FLAG(t)) {
+      if (FLAG(v)) {
+        struct tm *lc = localtime(TT.mtime ? &TT.mtt : &TT.hdr.mtime);
+        char perm[12], gname[12];
+
+        mode_to_string(TT.hdr.mode, perm);
+        printf("%s", perm);
+        sprintf(perm, "%u", TT.hdr.uid);
+        sprintf(gname, "%u", TT.hdr.gid);
+        printf(" %s/%s ", *TT.hdr.uname ? TT.hdr.uname : perm,
+          *TT.hdr.gname ? TT.hdr.gname : gname);
+        if (tar.type=='3' || tar.type=='4') printf("%u,%u", maj, min);
+        else printf("%9lld", (long long)TT.hdr.size);
+        sprintf(perm, ":%02d", lc->tm_sec);
+        printf("  %d-%02d-%02d %02d:%02d%s ", 1900+lc->tm_year, 1+lc->tm_mon,
+          lc->tm_mday, lc->tm_hour, lc->tm_min, FLAG(full_time) ? perm : "");
+      }
+      printf("%s", TT.hdr.name);
+      if (TT.hdr.link_target) printf(" -> %s", TT.hdr.link_target);
+      xputc('\n');
+      skippy(TT.hdr.size);
+    } else {
+      if (FLAG(v)) printf("%s\n", TT.hdr.name);
+      if (FLAG(O)) xsendfile_len(TT.fd, 1, TT.hdr.size);
+      else if (FLAG(to_command)) {
+        if (S_ISREG(TT.hdr.mode)) {
+          int fd, pid;
+
+          xsetenv("TAR_FILETYPE", "f");
+          xsetenv(xmprintf("TAR_MODE=%o", TT.hdr.mode), 0);
+          xsetenv(xmprintf("TAR_SIZE=%lld", TT.hdr.size), 0);
+          xsetenv("TAR_FILENAME", TT.hdr.name);
+          xsetenv("TAR_UNAME", TT.hdr.uname);
+          xsetenv("TAR_GNAME", TT.hdr.gname);
+          xsetenv(xmprintf("TAR_MTIME=%llo", (long long)TT.hdr.mtime), 0);
+          xsetenv(xmprintf("TAR_UID=%o", TT.hdr.uid), 0);
+          xsetenv(xmprintf("TAR_GID=%o", TT.hdr.gid), 0);
+
+          pid = xpopen((char *[]){"sh", "-c", TT.to_command, NULL}, &fd, 0);
+          // todo: short write exits tar here, other skips data.
+          xsendfile_len(TT.fd, fd, TT.hdr.size);
+          fd = xpclose(pid, fd);
+          if (fd) error_msg("%d: Child returned %d", pid, fd);
+        }
+      } else extract_to_disk();
+    }
+
+    free(TT.hdr.name);
+    free(TT.hdr.link_target);
+    free(TT.hdr.uname);
+    free(TT.hdr.gname);
+    TT.hdr.name = TT.hdr.link_target = 0;
+  }
+}
+
+// Add copy of filename (minus trailing \n and /) to dlist **
+static void trim2list(void *list, char *pline)
+{
+  char *n = xstrdup(pline);
+  int i = strlen(n);
+
+  dlist_add(list, n);
+  if (i && n[i-1]=='\n') i--;
+  while (i && n[i-1] == '/') i--;
+  n[i] = 0;
+}
+
+// do_lines callback, selects TT.incl or TT.excl based on call order
+static void do_XT(char **pline, long len)
+{
+  if (pline) trim2list(TT.X ? &TT.excl : &TT.incl, *pline);
+}
+
+void tar_main(void)
+{
+  char *s, **args = toys.optargs;
+  int len = 0;
+
+  // Needed when extracting to command
+  signal(SIGPIPE, SIG_IGN);
+
+  // Get possible early errors out of the way
+  if (!geteuid()) toys.optflags |= FLAG_p;
+  if (TT.owner) TT.ouid = xgetuid(TT.owner);
+  if (TT.group) TT.ggid = xgetgid(TT.group);
+  if (TT.mtime) xparsedate(TT.mtime, &TT.mtt, (void *)&s, 1); 
+
+  // Collect file list.
+  for (; TT.exclude; TT.exclude = TT.exclude->next)
+    trim2list(&TT.excl, TT.exclude->arg);
+  for (;TT.X; TT.X = TT.X->next) do_lines(xopenro(TT.X->arg), '\n', do_XT);
+  for (args = toys.optargs; *args; args++) trim2list(&TT.incl, *args);
+  for (;TT.T; TT.T = TT.T->next) do_lines(xopenro(TT.T->arg), '\n', do_XT);
+
+  // If include file list empty, don't create empty archive
+  if (FLAG(c)) {
+    if (!TT.incl) error_exit("empty archive");
+    TT.fd = 1;
+  }
+
+  // nommu reentry for nonseekable input skips this, parent did it for us
+  if (toys.stacktop) {
+    if (TT.f && strcmp(TT.f, "-"))
+      TT.fd = xcreate(TT.f, TT.fd*(O_WRONLY|O_CREAT|O_TRUNC), 0666);
+    // Get destination directory
+    if (TT.C) xchdir(TT.C);
+  }
+
+  // Get destination directory
+  TT.cwd = xabspath(s = xgetcwd(), 1);
+  free(s);
+
+  // Remember archive inode
+  {
+    struct stat st;
+
+    if (!fstat(TT.fd, &st)) {
+      TT.aino = st.st_ino;
+      TT.adev = st.st_dev;
+    }
+  }
+
+  // Are we reading?
+  if (FLAG(x)||FLAG(t)) {
+    struct tar_hdr *hdr = 0;
+
+    // autodetect compression type when not specified
+    if (!(FLAG(j)||FLAG(z)||FLAG(J))) {
+      len = xread(TT.fd, hdr = (void *)(toybuf+sizeof(toybuf)-512), 512);
+      if (len!=512 || strncmp("ustar", hdr->magic, 5)) {
+        // detect gzip and bzip signatures
+        if (SWAP_BE16(*(short *)hdr)==0x1f8b) toys.optflags |= FLAG_z;
+        else if (!memcmp(hdr->name, "BZh", 3)) toys.optflags |= FLAG_j;
+        else if (peek_be(hdr->name, 7) == 0xfd377a585a0000)
+          toys.optflags |= FLAG_J;
+        else error_exit("Not tar");
+
+        // if we can seek back we don't need to loop and copy data
+        if (!lseek(TT.fd, -len, SEEK_CUR)) hdr = 0;
+      }
+    }
+
+    if (FLAG(j)||FLAG(z)||FLAG(J)) {
+      int pipefd[2] = {hdr ? -1 : TT.fd, -1}, i, pid;
+      char *cmd[] = {"bzcat", 0};
+
+      if (FLAG(J)) cmd[0] = "xzcat";
+      else if FLAG(z) cmd[0]++;
+      xpopen_both(cmd, pipefd);
+
+      if (!hdr) {
+        // If we could seek, child gzip inherited fd and we read its output
+        close(TT.fd);
+        TT.fd = pipefd[1];
+
+      } else {
+
+        // If we autodetected type but then couldn't lseek to put the data back
+        // we have to loop reading data from TT.fd and pass it to gzip ourselves
+        // (starting with the block of data we read to autodetect).
+
+        // dirty trick: move gzip input pipe to stdin so child closes spare copy
+        dup2(pipefd[0], 0);
+        if (pipefd[0]) close(pipefd[0]);
+
+        // Fork a copy of ourselves to handle extraction (reads from zip output
+        // pipe, writes to stdout).
+        pipefd[0] = pipefd[1];
+        pipefd[1] = 1;
+        pid = xpopen_both(0, pipefd);
+        close(pipefd[1]);
+
+        // loop writing collated data to zip proc
+        xwrite(0, hdr, len);
+        for (;;) {
+          if ((i = read(TT.fd, toybuf, sizeof(toybuf)))<1) {
+            close(0);
+            xwaitpid(pid);
+            return;
+          }
+          xwrite(0, toybuf, i);
+        }
+      }
+    }
+
+    unpack_tar(hdr);
+    dirflush(0);
+
+    // Each time a TT.incl entry is seen it's moved to the end of the list,
+    // with TT.seen pointing to first seen list entry. Anything between
+    // TT.incl and TT.seen wasn't encountered in archive..
+    if (TT.seen != TT.incl) {
+      if (!TT.seen) TT.seen = TT.incl;
+      while (TT.incl != TT.seen) {
+        error_msg("'%s' not in archive", TT.incl->data);
+        TT.incl = TT.incl->next;
+      }
+    }
+
+  // are we writing? (Don't have to test flag here, one of 3 must be set)
+  } else {
+    struct double_list *dl = TT.incl;
+
+    // autodetect compression type based on -f name. (Use > to avoid.)
+    if (TT.f && !FLAG(j) && !FLAG(z)) {
+      char *tbz[] = {".tbz", ".tbz2", ".tar.bz", ".tar.bz2"};
+      if (strend(TT.f, ".tgz") || strend(TT.f, ".tar.gz"))
+        toys.optflags |= FLAG_z;
+      if (strend(TT.f, ".txz") || strend(TT.f, ".tar.xz"))
+        toys.optflags |= FLAG_J;
+      else for (len = 0; len<ARRAY_LEN(tbz); len++)
+        if (strend(TT.f, tbz[len])) toys.optflags |= FLAG_j;
+    }
+
+    if (FLAG(j)||FLAG(z)||FLAG(J)) {
+      int pipefd[2] = {-1, TT.fd};
+
+      xpopen_both((char *[]){FLAG(z)?"gzip":FLAG(J)?"xz":"bzip2", "-f", NULL},
+        pipefd);
+      close(TT.fd);
+      TT.fd = pipefd[0];
+    }
+    do {
+      TT.warn = 1;
+      dirtree_flagread(dl->data, FLAG(h)?DIRTREE_SYMFOLLOW:0, add_to_tar);
+    } while (TT.incl != (dl = dl->next));
+
+    writeall(TT.fd, toybuf, 1024);
+  }
+
+  if (CFG_TOYBOX_FREE) {
+    llist_traverse(TT.excl, llist_free_double);
+    llist_traverse(TT.incl, llist_free_double);
+    while(TT.hlc) free(TT.hlx[--TT.hlc].arg);
+    free(TT.hlx);
+    free(TT.cwd);
+    close(TT.fd);
+  }
+}