Install "zsh" on Ubuntu/Debian

install_zsh_ubuntu.sh

#!/bin/sh
# Build Zsh from sources on Ubuntu.
# From http://zsh.sourceforge.net/Arc/git.html and sources INSTALL file.
if ! which porg >/dev/null 2>&1; then
  echo 'A program manager "porg" is required.'
  echo 'Install it via the following command'
  echo ''
  echo '  curl -sL git.io/vXTo7 | bash'
  echo ''
  echo 'Ref: https://gist.github.com/lambdalisue/161aa84af9a9ff7d3bfe9decfabf656a'
  exit 1
fi
set -e

unset rep

atexit() {
  [[ -d "$rep" ]] && rm -rf $rep
}
trap atexit HUP INT QUIT TERM

rep=$(realpath $(mktemp -d zsh.XXXXXX))

# Some packages may be missing
sudo apt-get install -y git-core gcc make autoconf yodl libncursesw5-dev texinfo

git clone --depth 1 --single-branch http://git.code.sf.net/p/zsh/code $rep

cd $rep
./Util/preconfig
./configure --prefix=/usr/local \
            --enable-maildir-support \
            --enable-max-jobtable-size=256 \
            --enable-function-subdirs \
            --with-tcsetpgrp \
            --with-term-lib="ncursesw" \
            --enable-cap \
            --enable-pcre \
            --enable-readnullcmd=pager \
            --enable-custom-patchlevel=Debian \
            LDFLAGS="-Wl,--as-needed -g"

make -j $(grep -c '^processor' /proc/cpuinfo)
make check
sudo porg -lp 'zsh' 'make install'
sudo porg -lp 'zsh.info' 'make install.info'

atexit

https://git.io/vXLAa

curl -sL git.io/vXLAa | bash