Manipulation row order in file

Shell Programming and Scripting
1

Hello,
I am trying to replace the position of each row by the next row.
OS: Ubuntu 18.04, bionic
I'd appreciate your help.

input_file:

-O fileA
wget http://x.y.z./a
-O fileB
wget http://a.b.c./d
-O fileC
wget http://q.f.s/t
..
..
..
-O fileZZ
wget http://r.t.y/u

I expect:

wget http://x.y.z./a
-O fileA
wget http://a.b.c./d
-O fileB
wget http://q.f.s/t
-O fileC
..
..
..
wget http://r.t.y/u
-O fileZZ

or

wget http://x.y.z./a -O fileA
wget http://a.b.c./d -O fileB
wget http://q.f.s/t -O fileC
..
..
..
wget http://r.t.y/u -O FileZZ

I tried different combinations of below command but not as expected.

sed -n '{p;n;};h;p;n;p' input_file

many thanks
Boris

------ Post updated at 06:13 AM ------

Weird method but okay for me:

awk 'NR % 2 == 1' input_file > odd_lines
awk 'NR % 2 == 0' input_file > even_lines
paste -d'\n' even_lines odd_lines > expected_output

many thanks
Boris

2

Would this come close?

sed -n 'h;n;G;p' file
wget http://x.y.z./a
-O fileA
wget http://a.b.c./d
-O fileB
wget http://q.f.s/t
-O fileC
wget http://r.t.y/u
-O fileZZ
1 Like
3

Dear Rudic,
Could you please teach me how to catch the fish.
I looked up sed -help before opening this thread, but there was no info regarding n and p and other letters.
I'd appreciate if you would let us know how to find more info regarding functions of this notations

many thanks
Boris

4

My wisdom comes from the man pages: man sed , plus, infrequently, info sed .
And, DON'T forget, regular consumption of these forums! Many a trick I learned in here. Above little one copies a line into the hold buffer (h), reads the next line (n), appends from the hold buffer (G), and prints (p). It depends on the lines always coming in pairs.

1 Like
5

Dear Rudic,
It gives expected output. learnt that --help and man have not the same concept.

Many thanks
Boris

6

If, instead of switching every pair of lines in a file, you wanted to switch every line containing the string wget with the line preceding it, you could try:

ed -s input_file <<-EOF
	g/wget/ .-1m.
	,p
	Q
EOF

And, if after switching the order of those pairs of lines you also want to join them, you could try:

ed -s input_file <<-EOF
	g/wget/ .-1m.\\
		s/^/ /\\
		.-1,.j
	,p
	Q
EOF

or, if as in this example, you don't need to perform any parameter expansions in the here-document:

ed -s input_file <<-"EOF"
	g/wget/ .-1m.\
		s/^/ /\
		.-1,.j
	,p
	Q
EOF
1 Like
7

one awk:

awk 'FNR%2{f=$0;next}{print $0, f}' myFile
1 Like