How to grep "--"

Shell Programming and Scripting
1

Just looking for

cat file | grep "--"
2

I'm not clear on the question. Are you looking to match records containing a double hyphen?

Try:-

grep "\-\-" file

The problem could be just that the hyphen is a special character, so you need to use the backslash to define you string to use it as just some text.

I hope that this helps

Robin
Liverpool/Blackburn
UK

3

It worked. I tried without the quotes but obviously didn't apply. To show lines containing two hyphens and not more I use:

cat file | grep "\-\-" | grep -v "\-\-\-"
4

Excellent. Pleased to be of assistance.

Robin

5

See also Useless Use of Cat.

grep "\-\-" file | grep -v "\-\-\-"

Or you can do it all in one awk:

awk '/--/ && !/---/' file
6

Loved that one

 <file awk '/--/ && !/---/'
7

-- itself is the solution. If you ever need to grep these kind of words/strings etc, use "--" to disable to treat them as a switch

$ cat f3
--
-i
-v
$ 


$ grep -- -i f3
-i
$ grep -- -v f3
-v
$ grep -- -- f3
--

This also applies to other commands.

e.g.

$ touch -t
touch: option requires an argument -- t
Try `touch --help' for more information.
$ 
$
$ touch -- -t
$
$ rm -t
rm: unknown option -- t
Try `rm ./-t' to remove the file `-t'.
Try `rm --help' for more information.
$
$
$ rm -- -t
$

Hope it helps.

8

or use grep with "-e"

grep -e "--"
9

You can also grep for characters grep would mistake for parameters by 'disguising' them inside [].

grep "[-][-]" file

You can use the same trick, changing how a regex looks without changing its meaning, to prevent grep from grepping itself inside a ps listing, by the way. Much cleaner than | grep -v grep.

ps | grep '[p]rocessname'
10

Or:

grep \\--

(only the first - needs escaping)