Command can do the reverse of what the paste command does

pastetext processing

The paste command can merge multiple lines into one. For example, if I have a file test.txt and it contains:

original text

a
aa
aaa
b
bb
bbb
c
cc
ccc

I can use the command paste -s -d '\t\t\n' test.txt to get:

processed result

a   aa  aaa
b   bb  bbb
c   cc  ccc

I want to know if there is a reverse command that can do the reverse of paste. For example, If I have "processed result", how can I get "original text"?

Best Answer

There's no standard command.

You must do it your self, and depends on your input.

In this case:

tr '\t' '\n' <pasted_file.txt

will give you the original one.

Note that it assumes \t doesn't appear in your original file.

Related Solutions

Lum – A better paste command

Assuming you don't have any tab characters in your files,

paste file1 file2 | expand -t 13

with the arg to -t suitably chosen to cover the desired max line width in file1.

OP has added a more flexible solution:

I did this so it works without the magic number 13:

paste file1 file2 | expand -t $(( $(wc -L <file1) + 2 ))

It's not easy to type but can be used in a script.

Bash – Trying to add a newline to the paste command

Try this solution with two extra temporary files:

paste tmp1 tmp2 > tmp12
paste tmp4 tmp5 tmp6 > tmp456
paste -d "\n" tmp12 tmp3 tmp456 > tmp7

This solution was based on the assumption that the -d option selects the delimiter globally for all input files so it either be a blank or a newline. In a way this is true since later occurences of -d overwrite previous ones. However, as @DigitalTrauma pointed out we can supply more than one delimiter which will be used sequentially. So @DigitalTrauma's solution is more elegant than mine since it completely avoids additional temporary files.

One niche application for my solution would be the case in which one or delimiters with more than one character each have to be used. This should not be possible with just using the -d option.