Gfilui

I have a text file many thousands of lines long with ASCII and non-ACII characters. It is supposed to follow a pattern of

First line: only non-ASCII characters
Second line: only non-ASCII characters
Third line: only ASCII characters
Fourth line: mix of ASCII and non-ASCII characters

Unfortunately, the reality is that it looks something like the following example, where in the middle it is missing the line that mixes ASCII and non-ASCII characters:

日本語のみ
日本語のみ
English words only
English and 日本語
日本語のみ
日本語のみ
English words only
日本語のみ
日本語のみ
English words only
English and 日本語

Fortunately, as far as I can tell, it is only the line that mixes ASCII and non-ASCII characters that is sometimes absent. Meaning that what should be groups of 4 lines are sometimes groups of only 3.

To fix the file, I need to:

1. Search for every line with only ASCII characters.


2. Test the line following to see if it contains only non-ASCII.


3. If so, insert a placeholder line following the ASCII only line.

The result should be:

日本語のみ
日本語のみ
English words only
English and 日本語
日本語のみ
日本語のみ
English words only
+Aあ+
日本語のみ
日本語のみ
English words only
English and 日本語

(I chose to make the placeholder +Aあ+ so that it will conform to the mix of ASCII and non-ASCII as the lines it is standing in for.)

I've found I can use sed to insert new lines sed -e "/this is existing text/a'this is a new line'" < file.text. And I've learned I can search for ASCII characters with sed using LC_ALL=C and [d0-d127].

However, I'm unclear on how to make a conditional separate from the search. I mean, I could insert a line after every instance of ASCII only characters, but how do I make a search that inserts a line when an all ASCII line is found and the next line is only non-ASCII?

Please note that I am not particular about using sed. If an answer can be provided using Gedit, LibreOffice, or any command line operation, that would be great.

Based on your recent questions it sounds like you have an XY problem

Here's a sed solution based on @Zanna's answer to your previous question How do I search for lines in a file that only contain ASCII characters and then act on them?

$ LC_ALL=C sed -E '/^[d0-d127]+$/ $!N; s/n[^d0-d127]+$/n+Aあ+&/;' file
日本語のみ
日本語のみ
English words only
English and 日本語
日本語のみ
日本語のみ
English words only
+Aあ+
日本語のみ
日本語のみ
English words only
English and 日本語

Using awk:

awk '1; ! /^[x01-x7F]*$/ next getline !/[x01-x7F]/ print "+Aあ+" 1'

1. Print the input line unconditionally - 1 is a true condition, and the default action in that case is to print.


2. Then, if it isn't (!) entirely ASCII (/^[x01-x7F]*$/), skip processing more rules (proceeding to the next line, but processing rules from 1).


3. If it is entirely ASCII, we get the next line getline, and if that doesn't ! have any ASCII characters /[x01-x7F]/ in it, print your placeholder.


4. Finally print the line we read using getline.

I'm assuming that your 日本語のみ lines don't have half-width spaces or punctuation (. ! vs 。　！).