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What does “--” (double-dash) mean?

Can anybody explain me below things

i have file named "-xyz". if i try to remove or move that file using command line , it's unable to move. i tried below things :

[rahul@srv100 ~]# ls -lrt  -- "-xyz"
-rw-r--r-- 1 rahul rahul 0 Dec 19 08:06 -xyz
[rahul@srv100 ~]# mv "-xyz" xyz
mv: invalid option -- x
Try `mv --help' for more information.
[rahul@srv100 ~]# mv \-xyz xyz
mv: invalid option -- x
Try `mv --help' for more information.
[rahul@srv100 ~]# mv -\xyz xyz
mv: invalid option -- x
Try `mv --help' for more information.
[rahul@srv100 ~]# mv '-xyz' xyz
mv: invalid option -- x
Try `mv --help' for more information.

finally i rename that file using winscp, and after trying multiple ways i got one option and it's working.

mv -- '-xyz' xyz

Wish the help of "--", i created file/directory as below

mkdir -- --abc
touch -- -xyz

So my Question is what is this "--" in bash ? Please explain.

Community
  • 1
Rahul Patil
  • 24,711

3 Answers3

1

This is used to tell the command that after that point no more command options are accepted.

So

rm -- -abc

means that it will ignore the - from the abc.

for more information you can refer to: http://tldp.org/LDP/abs/html/special-chars.html

BitsOfNix
  • 5,117
  • 2
    Not really ignore the - from the -abc. Instead, it will not consider -abc to be an option, since after the --, no more options are interpreted, only arguments. – gniourf_gniourf Dec 21 '12 at 09:58
1

It's an indicator to the individual commands to stop interpreting further command line arguments as options.

Renan
  • 17,136
Anil Tallapragada
  • 11
1

As others have already mentioned -- is used to delimit options from arguments. If you execute a program and specify any arguments the program has no way of distinguishing if the specified arguments should be interpreted as a command line option or an argument. That is the reason why a prefix for options was introduced - / -- or / on windows, i.e. -rf,--help or /?

As you may have files beginning with a such an prefix or any other special name which could be interpreted -- was introduced to delimit command line options from normal arguments, i.e. every argument after -- will not be treated as a command line option but just as a argument. getopt (1), a standard solution to parse arguments, for example supports the -- delimiter which means any program using getopt automatically supports the -- delimiter.

If you want to work with files starting with special characters like - you can also just add ./ in front of them as they now don't start with - so they won't be interpreted as command line option, for your example it would be mkdir ./--abc

Ulrich Dangel
  • 25,369