I have the following variable.
echo "|${VAR1}|"
which returns
|
ABC
XYZ|
How can I remove the empty lines, preserving line breaks and using parameter expansion? So that it would become
|ABC
XYZ|
p.s.: I know how to do it using pipe sed, but I would like to avoid the extra SED process:
VAR1=`echo "${VAR1}" | sed '/^\s*$/d'`
Remove the leading newlines, then replace any consecutive newlines with a single one.
#! /bin/bash
var='
ABC
XYZ'
expected='ABC
XYZ'
shopt -s extglob
var=${var##+($'\n')}
var=${var//+($'\n')/$'\n'}
[[ $var == $expected ]] && echo OK
read the lines of the variable into an array, and remove the empty elements
var1=$'\nABC\n\nXYZ'
mapfile -t arr <<<"$var1"
declare -p arr # => declare -a arr=([0]="" [1]="ABC" [2]="" [3]="XYZ")
for ((i = ${#arr[@]} - 1; i >= 0; i--)); do
[[ -z ${arr[i]} ]] && unset "arr[i]"
done
declare -p arr # => declare -a arr=([1]="ABC" [3]="XYZ")
(IFS=$'\n'; echo "|${arr[*]}|") # in a subshell for temporary IFS setting
|ABC
XYZ|
for i in "${!arr[@]}" would also work, as that dumps all the indices at once before the loop starts.