Like short options, old options are single letters. However, old options
must be written together as a single clumped set, without spaces separating
them or dashes preceding them1. This set
of letters must be the first to appear on the command line, after the
tar program name and some white space; old options cannot appear
anywhere else. The letter of an old option is exactly the same letter as
the corresponding short option. For example, the old option ‘t’ is
the same as the short option -t, and consequently, the same as the
mnemonic option --list. So for example, the command ‘tar cv’ specifies the option -v in addition to the operation -c.
When options that need arguments are given together with the command,
all the associated arguments follow, in the same order as the options.
Thus, the example given previously could also be written in the old
style as follows:
$ tar cvbf 20 /dev/rmt0
Here, ‘20’ is the argument of -b and ‘/dev/rmt0’ is
the argument of -f.
On the other hand, this old style syntax makes it difficult to match
option letters with their corresponding arguments, and is often
confusing. In the command ‘tar cvbf 20 /dev/rmt0’, for example,
‘20’ is the argument for -b, ‘/dev/rmt0’ is the
argument for -f, and -v does not have a corresponding
argument. Even using short options like in ‘tar -c -v -b 20 -f /dev/rmt0’ is clearer, putting all arguments next to the option they
If you want to reorder the letters in the old option argument, be
sure to reorder any corresponding argument appropriately.
This old way of writing tar options can surprise even experienced
users. For example, the two commands:
tar cfz archive.tar.gz filetar -cfz archive.tar.gz file
are quite different. The first example uses archive.tar.gz as
the value for option ‘f’ and recognizes the option ‘z’. The
second example, however, uses z as the value for option
‘f’ — probably not what was intended.
Old options are kept for compatibility with old versions of tar.
This second example could be corrected in many ways, among which the
following are equivalent:
As far as we know, all tar programs, GNU and
non-GNU, support old options. GNU tar
supports them not only for historical reasons, but also because many
people are used to them. For compatibility with Unix tar,
the first argument is always treated as containing command and option
letters even if it doesn't start with ‘-’. Thus, ‘tar c’ is
equivalent to ‘tar -c’: both of them specify the
--create (-c) command to create an archive.
 Beware that if you precede options
with a dash, you are announcing the short option style instead of the
old option style; short options are decoded differently.
Published under the terms of the GNU General Public License