Recently I got to know of -- that is double-hyphen which is used to tell a command that the option list has ended and what follows should not be considered as a option. So,

grep --  'search_word' *

would search for the given search_word. But you could see a unexpected behavior if you remove -- and if there is a single file that start with -, which would switch on the option that match with the chars in filename.

What is this -- called ? Is there any technical term to this ?

  • 3
    See the debate on Why do unix-heads say “minus”? then double it. – manatwork Nov 22 '12 at 14:25
  • @manatwork No, square it! Should we say “minus dash” or “dash minus”? – Gilles 'SO- stop being evil' Nov 22 '12 at 23:12
  • I just pronounce it "--". – dubiousjim Jan 11 '13 at 13:40
  • I encounter regularity the cd -- and cd - phenomena. while cd -- means essentially just cd and thus change into your $HOME, cd - means put your self into previous directory. This becomes handy when you wanted to cd .. but as with german keyboard layout I mix it often up with cd --. cd - will then put you back. :D – math Sep 24 '13 at 7:33

The -- is working for tools which use getopt(3) to process command line arguments and many API that parse POSIX style options.

From the manual page of getopt(3):

The interpretation of options in the argument list may be cancelled by the option `--' (double dash) which causes getopt() to signal the end of argument processing and return -1.

I would then say it is called double dash

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  • But I'd bet there's some linguistic term for that. – Rob Nov 22 '12 at 14:12
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    getopt is not the only API that supports "--". Most APIs that parse POSIX style options in most languages support it. All POSIX utilities but echo and [ support it – Stéphane Chazelas Nov 22 '12 at 14:30
  • @StephaneChazelas Thanks I edited the answer – Matteo Nov 22 '12 at 14:50

The only two names which I've head in practise are "double dash" for referring to it aesthetically, and "end of options" for referring to it functionally.

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  • i've seen it refered to as 'last-option' as well. – Tim Kennedy Jan 11 '13 at 14:38

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