command to duplicate lines

[TheDash]

Hello members, I have a text file and I am looking for a way to duplicate lines in it. Above every line, a duplicate line should be inserted with comment in the front as shown below. Any help will be appreciated. Can a sed or awk command do the trick. Thank you in advance.

x
y
z

--x
x
--y
y
--z
z

 

[p5wizard]

[tt]awk '{print "--" $0; print}'[/tt]

should do it.

HTH,

p5wizard

 

[feherke]

Hi

Can a sed or awk command do the trick.

Just to answer your question, [tt]sed[/tt] also can do it :

sed 's/.*/--&\n&/' /input/file

[gray]# or[/gray]

sed 'h;s/^/--/;G' /input/file

Tested with GNU [tt]sed[/tt].

Feherke.

http://free.rootshell.be/~feherke/