#!/bin/sh
# Run this shell script to sort this list of positional parameters:
set -- \
'Hello' \
' 0 1 ' \
'' \
'*' \
'\0150\0151' \
"$(printf '\a\b\e\f\n\r\t\v')" \
'\a\b\e\f\n\r\t\v%%\\' \
'qwerty
uiop' \
'
new
lines
'
printf '====== NOT YET SORTED ======\n'
for param; do
printf '%s' "$param" | od -ab
done
quicksort() {
for param; do
# * Escape newlines (newline -> "\n" [two characters]).
# Rationale:
# * To be able to use newline as AWK record separator.
# * To be able to use it as the shell's $IFS for separating records.
# * Escape backslashes (backslash -> "\\" [two characters]).
# Rationale:
# * To distinguish between escaped newlines and the two-character
# string "\n" (escaped version: "\\n" [three-character string]).
# * To avoid special interpretation of backslashes when passed to
# `printf '%b' ...`.
#
# `sed` solution adapted from:
# https://unix.stackexchange.com/questions/761885/how-to-convert-all-newlines-to-n-in-posix-sh-strings
printf '%s\n' "$param" | LC_ALL=C sed '
:1
$ ! {
N
b1
}
s/\\/\\\\/g
s/\n/\\n/g'
done | awk -f ./quicksort.awk
}
# Create temporary file.
tmpfile="$(printf 'mkstemp(template)' \
| m4 -D template="${TMPDIR:-/tmp}/XXXXXX")" || exit 1
exec 3>"$tmpfile" 4<"$tmpfile" # Open tmpfile for writing and reading.
rm -f -- "$tmpfile"
quicksort "$@" >&3 3>&-
set --
while IFS='
'IFS= read -r line; do
# Unescape backslashes and newlines.
# To preserve trailing newlines (if any), insert a trailing character 'x'
# and later remove it.
elem="$(printf '%bx' "$line")"
set -- "$@" "${elem%x}"
done <&4 4<&-
printf '\n====== SORTED RESULTS ======\n'
for param; do
printf '%s' "$param" | od -ab
done
