What good are the signs '-' (minus) in any Linux/UNIX commands?

Asked Nov 09 '11 at 23:54

Active Nov 09 '11 at 23:54

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Possible Duplicate:
What does “--” (double-dash) mean?
Single dashes - for single-character options, but double dashes -- for words?

I was reading the man zip page and I found this examples:

[...] using the command

unzip -p backup | tar xf -

When [...] For example,

tar cf - . | zip | dd of=/dev/nrst0 obs=16k

is equivalent to

tar cf - . | zip - - | dd of=/dev/nrst0 obs=16k

I' like know the minus utility of these cases. Why two minus signs are written in the third case?

edited Apr 13 '17 at 12:36

Community

asked Nov 09 '11 at 23:54

omar

See: http://unix.stackexchange.com/questions/21852/single-dashes-for-single-character-options-but-double-dashes-for-words – jasonwryan Nov 10 '11 at 00:00
1

@jasonwryan That one doesn't seem related. This looks like a combination of Usage of dash (-) in place of a filename and What does "--" (double-dash) mean? though; I think I'm going with the latter since that's the actual question at the end – Michael Mrozek Nov 10 '11 at 00:07
Thanks both @jasonwryan and Michael. I found Michael's answer helpful – omar Nov 10 '11 at 00:30
2

There's no -- in this question. Its- -`, meaning create the ZIP file on standard output, and read the data to compress from standard input. So I'm pretty sure it's http://unix.stackexchange.com/questions/16357/usage-of-dash-in-place-of-a-filename. – Mikel Jun 25 '12 at 17:14

0 Answers0