How to replace a string with old string+appended string in vim

Question

This is the text in my file, which I'm editing with vim:

I want to change it to the the following content:

I have tried using this regular expression :%s/^.*$/\g<0>,\g<0>/g, but it's not working..

Answer 1

You can achieve that with the following replacement:

:%s/^.*$/&,&/
         ^ ^ 

The ^.*$ pattern will match the whole line, and & is a backreference to the whole match. So, the replacement is inserting back the whole match, a comma, and again the whole match.

NOTE: The ^ and $ in this ^.*$ pattern can be omitted, but a lot of people prefer to keep them explicit in the pattern to facilitate pattern readability and further pattern testing.

An alternative in case you want to avoid matching empty lines:

:%s/.\+/&,&/
    ^^^

The .\+ will match 1 or more characters.

Answer 2

using :s

%s/.*/&,&/

Note

• you don't need the ^ and $ since the regex is greedy.
• you don't need the g flag either.
• if you want to golf a bit, you don't need the last /

Or use normal command:

%norm! yaWA,^R"

or

%norm! yg_A,^R"

the ^R, you press <c-v><c-r>

Answer 3

Another way to do this without using regular expressions is to record a macro as you change the first line, then play the macro to change the remaining lines.

ggqay$A,<ESC>p+q4@a

Explanation:
gg move cursor to beginning of first line
qa start recording into register a
y$ copy the line
A go to insert mode at the end of the line
,<ESC> insert a comma and go back to normal mode
p paste the copy
+ move the cursor to the start of the next line
q stop recording
4@a play the macro four times to change the next four lines.

Answer 4

Execute these one by one:

:%s/abc/abc,abc/g
:%s/123/123,123/g
:%s/this/this,this/g
:%s/them/them,them/g
:%s/my/my,my/g

Similarly, replace the string with desired string for manipulating any string.