Re: [Help-bash] what's the best way to join two parts

[Greg Wooledge]

On Thu, Dec 29, 2011 at 11:26:12PM +0800, lina wrote:
> $ cat a_3.txt
> aaa
> bbb
> 
> 123
> 321
> 
> what if I want to join two parts together, the output wish to be
> 
> aaa 123
> bbb 321

Read the first part into an array (or a temp file)....

> and then
> paste b_1.txt b_2.txt

So you already know about the temp file answer, but you don't want to
do that.  OK.  Then let's use an array:

#!/usr/bin/env bash
# Load the first part of the file into array "arr", and stop reading when
# we find a blank line.
unset arr i
while read -r; do
  if [[ $REPLY = "" ]]; then
    break
  fi
  arr[i++]=$REPLY
done

# Now continue reading the second part of the file.
i=0
while read -r; do
  echo "${arr[i++]} $REPLY"
done