[TUHS] tar on v6 not creating directories on v6

Will Senn will.senn at gmail.com
Sun Dec 13 07:53:54 AEST 2015


I'm stuck trying to determine what is going on with v6tar on v6. It 
seems to work ok for files, but gets confused with subdirectories. I set 
up a test folder structure:


then I created a tarball
tar cvf t.tar t

then I tried to extract the tarball. It made a mess:
# tar xvf t.tar

Tar: blocksize = 17
y ?
tar: t/ken/prf.c - cannot create
y ?
y ?
tar: t/dmr/vs.c - cannot create
y ?
y ?
tar: t/dmr/vt.c - cannot create

That was ugly and all of it was output. What exactly did I wind up with?:
# ls -l
total 19
drwxrwxrwx  2 root       32 Oct 10 12:54 y
-rw-rw-rw-  1 root     8704 Oct 10 12:54 t.tar

Ugh. Probably don't need the y directory...
# rmdir y
y ?
# ls y
y not found

Wow! It appears that I am unable to delete the y directory or list it by 
name. That can't be good. Any ideas of how to remove this directory are 

Not to be deterred by one small failure, I copied the same tarball over 
to v7 on the off chance that maybe v6tar isn't really for v6, but more 
for moving files(and directories) over to v7 as Haley and Ritchie 
describe, and lo and behold tar on v7 is able to extract both files and 
directories from the same tarball without any trouble:

# tar xvf t.tar
Tar: blocksize = 17
x t/ken/prf.c, 2301 bytes, 5 tape blocks
x t/dmr/vs.c, 1543 bytes, 4 tape blocks
x t/dmr/vt.c, 834 bytes, 2 tape blocks

# ls -l
total 18
drwxrwxr-x 4 root       64 Dec 31 19:27 t
-rw-rw-r-- 1 root     8704 Dec 31 19:27 t.tar

# ls t

# ls t/dmr

# ls t/ken

Interesting. After looking at the tar source, the question marks in the 
output appear to be coming from somewhere outside of tar (perhaps mkdir 
or chown?). Also, the "cannot create" message comes from the following 
snippet of the tar source, which looks reasonable:
if ((ofile = creat(dblock.dbuf.name, stbuf.st_mode & 07777)) < 0) {
                         fprintf(stderr, "tar: %s - cannot create\n", 

I think this error is simply an effect related to the failure to create 
the necessary directories properly. The code to do that looks pretty 
register char *name;
         register char *cp;
         int i;
         for (cp = name; *cp; cp++) {
                 if (*cp == '/') {
                         *cp = '\0';
                         if (access(name, 01) < 0) {
                                 if (fork() == 0) {
                                         execl("/bin/mkdir", "mkdir", 
name, 0);
"mkdir", name, 0);
                                         fprintf(stderr, "tar: cannot 
find mkdir!\n");
                                 while (wait(&i) >= 0);
                                 chown(name, stbuf.st_uid, stbuf.st_gid);
                         *cp = '/';

I speculate that chown is causing the "?" to be displayed. Is it safe 
enough for me to add printf statements around this code to see what's 
going on, or is there a better approach?



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