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user784637
Asked: 2012-01-09 19:32:57 +0800 CST

tar -cvfz command results in error message unless I omit the hyphen before 'cvfz' [duplicate]

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Possible Duplicate:
sudo tar cvpzf exiting with failure due to previous error

When I run the command

tar -cvfz backup.tar.gz somedirectory

I get the following sterr

tar: Exiting with failure status due to previous errors

However when I omit the preceding hyphen from -cvfz everything seems to work just fine. Is there a known reason for why the hyphen is preventing me from tar'ing my files?

bash

1 Answers

  1. Best Answer

    I'm not sure why tar cvfz works, when accourding to a quick scan of the man page and my experience, a hyphen is standard practice. Maybe it's a BSD compatibility thing (like ps).

    At any rate, your syntax is incorrect. -f takes the next argument as the filename to compress to. In this case, that filename is z, which isn't what you expected. Here's a sample of the output so you can see what I mean:

    $ tar -cvfz test.tar.gz scott
tar: test.tar.gz: Cannot stat: No such file or directory
scott/
scott/netx/
scott/netx/locks/
scott/netx/locks/netx_running
tar: Exiting with failure status due to previous errors

    An ls shows a file called z. The file command reveals that it's an uncompressed tar archive. It's uncompressed because the -z argument wasn't passed. And the error message came from trying to add the non-existant file test.tar.gz to the archive.

    Simply reorder the options and you'll be OK:

    tar -czvf test.tar.gz some/directory

    If you always make the -f the last argument, you'll be fine. By the way, remember that short options (one-letter options) that take arguments don't normally require a space between the option and the argument.

    EDIT: By the way, if the form without the hyphen is a BSD-compatibility thing or something like that, then it's likely that the way that tar is invoked in such an environment is different, and doesn't require the f flag to specify the input file, but works more like cp or something. But this is just speculation based on comparison with ps (q.v.).

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