如何在 AWK 中填充 CSV 中的空单元格？

Question

I have a CSV file like this, with @ as the delimiter:

Chapter 1@This is some text.
        @This is some more text.
        @This is yet some more text.
Chapter 2@This is some text.
        @This is some more text.
        @This is yet some more text.

The first column contains the chapter number. The second column contains the text of the chapter.

I need to fill down all of the chapter number in column A, such that any empty cells below are filled with the chapter number. Eg, the output would be this:

Chapter 1@This is some text.
Chapter 1@This is some more text.
Chapter 1@This is yet some more text.
Chapter 2@This is some text.
Chapter 2@This is some more text.
Chapter 2@This is yet some more text.

How can I fill down all of the empty cells in column A of the table?

Answer 1

You can use awk like this:

awk  'BEGIN{FS=OFS="@"} {if ($1 ~ /^[ \t]*$/) $1=ch; else ch=$1} 1' file

Chapter 1@This is some text.
Chapter 1@This is some more text.
Chapter 1@This is yet some more text.
Chapter 2@This is some text.
Chapter 2@This is some more text.
Chapter 2@This is yet some more text.

Using a simple regex check we verify if $1 is not-empty then we set variable ch as name of the first chapter. Then in next subsequent lines we set chapter name to the value we've stored in variable as name of the first chapter. Then in next subsequent lines we set chapter name to the value we've stored in variable ch`.

Answer 2

Other way using awk

Input

$ cat file
Chapter 1@This is some text.
        @This is some more text.
        @This is yet some more text.
Chapter 2@This is some text.
        @This is some more text.
        @This is yet some more text.

Output

$ awk 'BEGIN{FS=OFS="@"}/^[ \t]+/{$1=c}{c=$1}1' file
Chapter 1@This is some text.
Chapter 1@This is some more text.
Chapter 1@This is yet some more text.
Chapter 2@This is some text.
Chapter 2@This is some more text.
Chapter 2@This is yet some more text.

$ awk 'BEGIN{FS=OFS="@"}/^[^\t ]+/{c=$1}{$1=c}1' file
Chapter 1@This is some text.
Chapter 1@This is some more text.
Chapter 1@This is yet some more text.
Chapter 2@This is some text.
Chapter 2@This is some more text.
Chapter 2@This is yet some more text.

Answer 3

Try this solution -

awk -F@  '$1!~/^[[:space:]]+/ {h=$1FS} {print ($1!~/^[[:space:]]+/? $0 : h$2)}' f
Chapter 1@This is some text.
Chapter 1@This is some more text.
Chapter 1@This is yet some more text.
Chapter 2@This is some text.
Chapter 2@This is some more text.
Chapter 2@This is yet some more text.