Hi

I have a list which looks like:

I want to get something like:

I tried:
to make }},\n} become }}}. But it only gave me the same result. I do not know what's wrong.

Any help would be greatly appreciated. Thanks!

Actually it is not a simple substitution. Your requirement can be summarized as:
1) leading { must be printed out without newline
2) the last line before the trailing } must have the last comma removed
3) the trailing } must be printed out at the end of the preceding line.
Moreover we cannot know when the trailing } will occur if we don't read the next line. Translated in awk:
This assumes the last line of input contains

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Thank you very much for your solution. I tried your code, but it also remove the comma between the }}} and the next {{{. It gave me the output:

However, what I need is:
But I would thank you all the same for your kind help. If you have bit more time and mood, welcome to improve the code. Thanks!

Hey cristal, if you fully understand the suggested code, you should be able to do a little modification. I still don't know what are your awk skills and knowledge, anyway the line of code
should read:

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Is this the idea:

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OK, Thanks colucix. I should apologize that it has nothing to do with my AWK knowledgeable. My real level should be approximately beginner+ level.

Frankly speaking, I just not read your code carefully. Sorry! I was lazy, but at least I am frank enough. OK, now I see, it is just simple problem, I should be able to figure it out. I will try to not so lazy in the future. Thanks for your help and kind reminding.

Thanks grail, would you mind explain a bit the meaning of the variable pre and the way to use it? I would thank for your future explanation.

No problem, I didn't mean to state you're lazy.. I just wanted to be sure about your level. I hope our suggestions will aid to improve your awk knowledge, since it's a very powerful tool and it can help you to spare a lot of time especially when dealing with complex tasks.

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As per colucix's example, pre simply hold the previous line of data.

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Thanks colucix! This time, I read your code carefully. I have several question about your code. Please allow me to analyze your code step by step and propose my questions for each part.

Part 1.
In this part the pattern NR == 1 means only for the first line then do the action set previous line to be the content of the file. Because now the content of the file is just "{", then pre equal to "{".

But I do not know why you do this?
You do not print out anything at this step, you just only set pre to "{".
When line number is bigger than 1 then pre can be "{" too (when NR == 2), or something else (when NR > 2). I mean, when liner number bigger than 1, the pre will be re-set, so what the point here you set pre to "{" and do not print anything?
Without this part, I got the output the first line empty then other lines are the same.
Is that related to "1) leading { must be printed out without newline"? How do you achieve it?

Part 2.
This is clear for me that it is doing job 2) the last line before the trailing } must have the last comma removed. For this part, no questions.

Part 3.
This for lines with number larger than 1, when the previous line match "{".
This is can be only one situation, when the line and the previous line are something like
For example the 2nd line, NR equal to 2 which is bigger then 1. now pre is the content of the first line "{". AWK will print "{" at line no.2.

My question is in fact the line no.2 in the new file should be {{1.50},{5.1,26}} which is the 3rd line of the old file. How do you achieve this?

Part 4.
This is for lines with number larger than 1, when the previous line do not match "},", then print the previous line. This can be two situations:
First situation, when the previous line is something like {{1.50},{3.5,26]}, it print out it.
So, for line no.3 for example, it print out line no.2. But what is the content of line no.2 now? Because I do not understand other part of the code, I do not sure if this is correct.

Second situation, when the previous line is {, then the code to same thing with Part.2.
Why has this redundant overlap? Is that necessary? Again, because I do not understand other parts of the code, I do not know what the meaning here.

Part 5.
Why you set at the end of the code that pre to $0?
Without this line I out the output
Could you explain why?

Sorry for so many questions. I tried really hard to understand the real meaning of the code and relate its logic with my awk knowledge and practice in this specific case. I think this is the best way to learn awk. So, if you could find a bit time to explain it, I would greatly appreciate! I know these 5 parts actually are related with each other. So, may be some questions can not be explained just for the specific part. Please explain in any way you wish.

I understand that you are new to awk, but most of your questions are answered by your own requirements.

The very first one being, if a line contains 'blah' and the next line is 'blah' then do something. The only way to achieve this result is to have at hand
both copies of information, hence the variable pre always contains the previous line. So instead of looking at each part of the code in isolation you need to remember
that at any point you will have the current line, $0, and the previous line, pre. The only exception to this rule is when the code first starts, hence the line:
The code requires that you will always have a value in pre, so this merely sets pre and no other code is executed as everything else requires NR to be not 1.
Incorrect, it will print this at the first line of the new output.
Are you saying this is not currently being output correctly? The code provided does output this as line 2 for me.
Incorrect. The ^ at the start of the regular expression means that the following pattern is at the start of the line which is not the case with your example.
Incorrect. No parts of the code refer to {,
As originally stated at the beginning of this post, pre is always set to the value of the previous line which will need to happen some where in the code.

OK, let me propose my question in a simple language:

How do you move "{" and "{{1.00},{3.4,23}}," from
into a same line, become:
?
Thanks!

I do not understand how this is anymore simple than the original question and consequently the solution is the same. The only difference is that the final line must still be '},' as
colucix pointed out in post # 2

Sorry, I do not understand why it is incorrect here. Because, the condition is:
That means when the line is not match }, which start from beginning of the line, it print pre.
No matter pre = "{" or pre = "{{1.00},{3.4,23}}," both fulfill the condition that the starting of the line of pre doeNOTs NOT match "},"(pre !~ /^},/). Is that true?

If so, when awk is reading the second line of the input file, the pre store the value in the first line that is "{" which is fulfill the condition:
and at the same time it fulfill the other condition:
Then, at the first line of the output file, it should print out "{{<end-line-character>", then set the pre to $0 which is the content of the second line of the input file ("{{1.50},{3.5,26}},").And then at the second line of the output file it will print out this new pre. So, the output file should look like:
I know this is a wrong understanding. But I do not know where I made the mistake. I know now I become too annoying and I am really sorry for taking so much time from you. But this step is really crucial for me to understand awk and do my own scripting more freely. I need do understand it!!! Of course, ignore it, if you do not have time. I would thank you all the same!

My bad ... at 3am I missed the not (!)

The full piece of code is:
As per normal if constructs, once the if has been matched the else will never be entered (and vice versa). So in answer to the statements:
This is incorrect as only the if will be entered should pre contain '^{$'

Let me know if this clears it up for you?

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