Move Last Four Lines To Second Row In Text File

Question

I need to move the last 4 lines of a text file and move them to the second row in the text file.

I'm assuming that tail and sed are used but, I haven't much luck so far.

Answer 1

Here is a head and tail solution. Let us start with the same sample file as Glenn Jackman:

$ seq 10 >file

Apply these commands:

$ head -n1 file ; tail -n4 file; tail -n+2 file | head -n-4
1
7
8
9
10
2
3
4
5
6

Explanation:

• head -n1 file

  Print first line

• tail -n4 file

  Print last four lines

• tail -n+2 file | head -n-4

  Print the lines starting with line 2 and ending before the fourth-to-last line.

Answer 2

If I'm assuming correctly, ed can handle your task:

seq 10 > file

ed file <<'COMMANDS'
$-3,$m1
w
q
COMMANDS

cat file

1
7
8
9
10
2
3
4
5
6

lines 7,8,9,10 have been moved to the 2nd line

$-3,$m1 means, for the range of lines from "$-3" (3 lines before the last line) to "$" (the last line, move them ("m") below the first line ("1")

Note that the heredoc has been quoted so the shell does not try to interpret the strings $- and $m1 as variables

If you don't want to actually modify the file, but instead print to stdout:

ed -s file <<'COMMANDS'
$-3,$m1
%p
Q
COMMANDS

Answer 3

Here is an awk solution:

seq 10 > file
awk '{a[NR]=$0} END {for (i=1;i<=NR-4;i++) if (i==2) {for (j=NR-3;j<=NR;j++) print a[j];print a[i]} else print a[i]}' file
1
7
8
9
10
2
3
4
5
6