Bash merge two specific lines into one

Question

I have a file that consists of two repeatedly occurring lines.

line1
     line2
line1
     line2
line1
     line2

I want to merge them so that the output file would look like:

line1 line2
line1 line2
line1 line2

Unfortunately I didn't succeed. In notepad++ I could do something like:

search: (line1)(\r\n)
replace: \1

Here I wanted to do the same but this:

sed -E 's/(line1)(\n)/\1/' my_file

doesn't work

You'll need the `N` command in sed to do this: `sed '{N;s/line1\n/line1/;}` See https://stackoverflow.com/questions/7852132/sed-join-lines-together — joanis, Jul 22 '19 at 13:47
Probably `sed -Ez 's/(line1)\r?\n/\1/' my_file` will work for you (with GNU sed) — Wiktor Stribiżew, Jul 22 '19 at 13:54
Or `sed 'N;s/line1[[:space:]]*/line1 /' my_file` to remove extra leading spaces from line2 as well. — Léa Gris, Jul 22 '19 at 13:58

score 1 · Accepted Answer · answered Jul 22 '19 at 13:48

1

You can use paste and tr for this:

cat file | paste -d" " - - | tr -s ' '

line1 line2
line1 line2
line1 line2

answered Jul 22 '19 at 13:48

Paul Dawson

This one merged only first two lines. The rest remained unchanged. Nevertheless thank you. – Z.Szymon Jul 22 '19 at 13:53
1

How do you mean? It will go through the whole file and print alternate lines on one line. You could use `paste -d" " - - -` will print every 3 lines onto one and so forth. – Paul Dawson Jul 22 '19 at 13:56
Ok than it works. Is there any way to not specify dashes? Can't it go to the end of the file itself? – Z.Szymon Jul 22 '19 at 13:59
No, that's part of the command `- -` is 2 lines `- - -` is 3 lines `- - - -` is 4 lines etc. – Paul Dawson Jul 22 '19 at 14:01
1

Oh now I understand. It was working the whole time what I forgot to mention was that I had empty lines in between and hence I thought it was broken. Now I think that I like your answer the most. – Z.Szymon Jul 22 '19 at 14:04

anubhava · Answer 2 · 2019-07-22T14:08:41.503

1

sed doesn't match across the line. You may use perl in slurp mode:

perl -0777 -pe 's/(line1)\R+\h+/$1 /g' file

line1 line2
line1 line2
line1 line2
line1 line2

edited Jul 22 '19 at 14:08

answered Jul 22 '19 at 13:50

anubhava

Awesome this is exactly what I wanted. Doesn't sed really have any flag or something to match the whole line? – Z.Szymon Jul 22 '19 at 13:55
There are four spaces between line1 and line2 – Paul Dawson Jul 22 '19 at 13:57
@Z.Szymon: Using sed you can do: `sed -E 'N;s/(line1)\n/\1/;' file` – anubhava Jul 22 '19 at 13:58
@anubhava it has taken care of only the first two lines, the rest remained unchanged – Z.Szymon Jul 22 '19 at 14:01
Strangely on my sed or perl, it is changing full file. – anubhava Jul 22 '19 at 14:04
It was working the whole time what I forgot to mention was that I had empty lines in between and hence I thought it was broken. I'm sorry. – Z.Szymon Jul 22 '19 at 14:07
2

@AlfredE.Noobman: Thanks, I overlooked space removal requirement in question, It is fixed now. – anubhava Jul 22 '19 at 14:07
1

@Z.SzymonL Then you may need `perl -0777 -pe 's/(line1)R+\h+/$1 /g' file` – anubhava Jul 22 '19 at 14:08

2 Answers2