[vox]$ echo foo > zzz
[vox]$ chmod 000 zzz
[vox]$ tar cvf /dev/null zzz
zzz
[vox]$ echo $?
0
[vox]$ tar cvf zzz.tar zzz
tar: zzz: Cannot open: Permission denied
tar: Exiting with failure status due to previous errors
[vox]$ echo $?
2

[vox]$ tar cvf - zzz >/dev/null
zzz
[vox]$ echo $?
0
[vox]$ tar cvf - zzz |cat >/dev/null
tar: zzz: Cannot open: Permission denied
tar: Exiting with failure status due to previous errors
[vox]$