How to copy first four characters of every line to the end of that same line?

Question

Given a series of lines that look similar to this:

2001 "Some Kind of Title," Author's Name, Publication Name, 1 Mar.
2002 "Some Kind of Title," Author's Name, Publication Name, 12 Oct.
2003 "Some Kind of Title," Author's Name, Publication Name, 8 Apr.
2004 "Some Kind of Title," Author's Name, Publication Name, 3 Jun.

Is there a way that I could grab those first four characters (the year), and copy them to the end of the line, so that it looks like this:

2001 "Some Kind of Title," Author's Name, Publication Name, 1 Mar. 2001
2002 "Some Kind of Title," Author's Name, Publication Name, 12 Oct. 2002
2003 "Some Kind of Title," Author's Name, Publication Name, 8 Apr. 2003
2004 "Some Kind of Title," Author's Name, Publication Name, 3 Jun. 2004

Answer 1

:% s/\v^(\d{4})(.*)$/\1\2 \1/ 

is one way to do it

• \v magic option, to avoid having to escape grouping ()
• ^ start of line
• \d{4} match exactly four digits
• .* rest of line
• \1 \2 has the matched pattern within ()

edit: @Jair Lopez mentions in comments, the regular expression can be further improved:

:% s/\v^(\d{4}).*/& \1/ 

or the equivalent

:% s/\v^(\d{4}).*/\0 \1/ 

• & and \0 contains the whole matched pattern

For further reading, vimregex and regex FAQ

Answer 2

And a solution with a macro:

qqyiwA <Esc>pj0q

Which means:

qq   Record the macro in the register q
yiw  Yank the text described by the text object iw (inner word): The date
A <Esc>   Append a white space to the end of the line and go back to insert mode
p    Paste the date
j0   Place your cursor on the first column of the next line (to be able to repeat the macro)
q    Stop recording

You can then replay the macro as many time as you have line with 3@a.

Edit As @evilsoup mentioned it in the comments, a more effective way to execute the macro on all the lines of the buffer is to use:

:%normal @q

You can of course replace % by a range describing the lines to modify.

Answer 3

Here is the way that I would do it:

:%norm y4lA <C-o>p

Explanation:

:%norm                     "Apply the following keystrokes to every line:
       y4l                 "Yank 4 letters. You could also do 'yiw'
          A                "Add a space to the end
            <C-o>          "Do a single normal command
                 p         "Paste

Answer 4

If you have access to standard UNIX commands, you could use AWK:

:%!awk '{print $0" "$1}'

Answer 5

I think that the existing mechanisms to do this are better, but it is also possible to do this using visual block mode.

Copy the dates:

gg          # Go to the top of the file
<ctrl>y     # Enter visual block mode
G           # Go to the bottom of the file
w           # Select the first word
"jy         # Copy in to the j register

Pad the end of first line:

gg      # Top of file
A       # Append the line
        # Some spaces
<ESC>   # Return to command mode

Paste:

gg 
# Move right to the length of the longest line
"jp   # Paste the block

Answer 6

From a unix command line (or windows if you have unix command line tools installed)

sed -e "s/\(....\)\(.*\)/\1\2 \1" < inputFile > outputFile