Remove text file newlines with sed

remove_newline.sh

#!/usr/bin/env sh

# How to remove all newlines (\n) from a text file by using sed ? (from stackoverflow)

replace=${1}
file=${2}

sed ':a;N;$!ba;s/\n/${replace}/g' ${file}

# This will read the whole file in a loop, then replaces the newline(s) with a space.

# Explanation:

#    Create a label via :a.
#    Append the current and next line to the pattern space via N.
#    If we are before the last line, branch to the created label $!ba ($! means not to do it on the last line as there should be one final newline).
#    Finally the substitution replaces every newline with a space on the pattern space (which is the whole file)