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I've got a text file given, and the results and the counts vary (date, link and id can be anything). However, the count of dates, links and id's is always the same (so n - n - n for any positive integer n). Is n a positive integer, then the lines n, (n + k/3) and (n+2(k/3)), where k is the number of all lines, belong together.

As en example, I picked out n=3. So lines (1 | 4 | 7), (2 | 5 | 8) and (3 | 6 | 9) belong together:

Today, 17:09
Yesterday, 09:44
08.09.2020
07.09.2020
06.09.2020
/s-show/Link111...
/s-show/Link211...
/s-show/Link311...
/s-show/Link411...
/s-show/Link511...
id="1222222222"
id="2222222222"
id="3222222222"
id="4222222222"
id="5222222222"

I would like to sort the text file as the following:

id="1222222222"Today, 17:09/s-show/Link111...
id="2222222222"Yesterday, 09:44/s-show/Link211
id="3222222222"08.09.2020/s-show/Link311
id="4222222222"07.09.2020/s-show/Link411
id="5222222222"06.09.2020/s-show/Link511

In a former question, I only had two categories (date and link) and was adviced to do it like the following:

lc=$(wc -l <Textfile); paste -d '' <(head -n $((lc/2)) Textfile) <(tail -n  
$((lc/2)) Textfile)

However, here I have 3 categories and the head and tail command won't let me read only the lines in the middle. How could this be solved?

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  • You can combine head and tail to get content in the middle. (It's not what I would actually choose to do, but it's certainly something you can do). Commented Sep 8, 2020 at 22:58
  • 1
    ...in terms of what I'd actually do, I wouldn't choose to use bash for the job at hand at all. A programming language with access to seek() and tell() calls will allow a much more efficient implementation. Commented Sep 8, 2020 at 23:00
  • 1
    ...as for your immediate question, though -- do you consider How can I extract a predetermined range of lines from a text file on UNIX a duplicate? As I understand it, it's narrowly addressing the part of your problem you don't currently know how to do. Commented Sep 8, 2020 at 23:03
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    paste file1 file2 file3. Which is to say, if you have three separate files, the whole problem becomes completely trivial. Commented Sep 9, 2020 at 0:00
  • 1
    ...if you really don't want tabs added, add the -d argument to paste, as in, paste -d '' file1 file2 file3. Commented Sep 9, 2020 at 0:03

1 Answer 1

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Leveraging the techniques taught in How can I extract a predetermined range of lines from a text file on Unix? --

#!/usr/bin/env bash

input=$1
total_lines=$(wc -l <"$1")
sections=$2

lines_per_section=$(( total_lines / sections ))
if (( lines_per_section * sections != total_lines )); then
  echo "ERROR: ${total_lines} does not evenly divide into ${sections} sections" >&2
  exit 1
fi

start=0
ranges=( )
for (( i=0; i<sections; i++ )); do
  ranges+=( "$start:$(( start + lines_per_section ))" )
  (( start += lines_per_section ))
done

get_range() { sed -n "$(( $1 + 1 )),$(( $2 ))p;$(( $2 + 1 ))q" <"$input"; }
consolidate_input() {
  if (( $# )); then
    current=$1; shift
    paste <(get_range "${current%:*}" "${current#*:}") <(consolidate_input "$@")
  fi
}

consolidate_input "${ranges[@]}"

But don't do that. Just put your three sections in three separate files, so you can use paste file1 file2 file3.

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Okay the paste file1 file 2 file3 command with -d ' ' will do nicely.

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