build-bash.sh

#!/bin/bash
echored () {
	echo "${TEXTRED}$1${TEXTRESET}"
}
echogreen () {
	echo "${TEXTGREEN}$1${TEXTRESET}"
}
usage () {
  echo " "
  echored "USAGE:"
  echogreen "To check patches are correct: check"
  echogreen "VER argument below must be applied with check"
  echored "Otherwise, Valid arguments are:"
  echogreen "NDK=      (Default: r18b)"
  echogreen "VER=      (Default: 4.4)"
  echogreen "ARCH=     (Default: arm) (Valid Arch values: arm, arm64, aarch64, x86, i686, x86_64)"
  echogreen "API=      (Default: 21)"
  echored "Note that the minimum API for arch64 and x86_64 is 21 (Lollipop)!"
  echored "Note that case insensitive file systems such as NTFS will have files overwritten during NDK extraction!"
  echored "It's recommended to use a case senstivie file system such as ext4 instead although this has seemingly no impact in this case"
  echo " "
  exit 1
}
check_patches () {
  echogreen "Checking patches"
  [ -z $VER ] && { echored "Version not defined!"; exit 1; }
  [[ $(wget -S --spider http://mirrors.kernel.org/gnu/bash/bash-$VER.tar.gz 2>&1 | grep 'HTTP/1.1 200 OK') ]] || { echored "Invalid Bash VER! Check this: http://mirrors.kernel.org/gnu/bash/ for valid versions!"; usage; }
  setup_bash
  apply_patches
  echogreen "Patches are good!"
  exit 0
}
apply_patches() {
  cd $DIR/bash_android/bash-$VER
  echogreen "Applying patches"
  for i in {001..050}; do
    wget https://mirrors.kernel.org/gnu/bash/bash-$VER-patches/bash$PVER-$i 2>/dev/null
    if [ -f "bash$PVER-$i" ]; then
      patch -p0 -i bash$PVER-$i
      rm -f bash$PVER-$i
    else
      break
    fi
  done
  for i in $DIR/patches/*; do
    PFILE=$(basename $i)
    cp -f $i $PFILE
    sed -i "s/4.4/$VER/g" $PFILE    
    patch -p0 -i $PFILE
    [ $? -ne 0 ] && { echored "Patching failed! Did you verify line numbers? See README for more info"; exit 1; }
    rm -f $PFILE
  done
}
setup_bash() {
  mkdir $DIR/bash_android 2>/dev/null
  cd $DIR/bash_android
  echogreen "Fetching bash $VER"
  rm -rf bash-$VER Toolchains
  [ -f "bash-$VER.tar.gz" ] || wget http://mirrors.kernel.org/gnu/bash/bash-$VER.tar.gz
  tar -xf bash-$VER.tar.gz
}

TEXTRESET=$(tput sgr0)
TEXTGREEN=$(tput setaf 2)
TEXTRED=$(tput setaf 1)
DIR=`pwd`
CHECK=false
OIFS=$IFS; IFS=\|; 
while true; do
  case "$1" in
    -h|--help) usage;;
    "") shift; break;;
    NDK=*|VER=*|ARCH=*|API=*) eval $1; shift;;
    check) CHECK=true; shift;;
    *) echored "Invalid option: $1!"; usage;;
  esac
done
IFS=$OIFS

$CHECK && check_patches
[ -z $NDK ] && NDK=r18b
[[ $(wget -S --spider https://dl.google.com/android/repository/android-ndk-$NDK-linux-x86_64.zip 2>&1 | grep 'HTTP/1.1 200 OK') ]] || { echored "Invalid Android NDK! Check this:https://developer.android.com/ndk/downloads/ for latest versions!"; usage; }
[ -z $VER ] && VER=5.0
case $VER in
  5*) mv -f $DIR/patches_5 $DIR/patches;;
  *) mv -f $DIR/patches_4 $DIR/patches;;
esac
[[ $(wget -S --spider http://mirrors.kernel.org/gnu/bash/bash-$VER.tar.gz 2>&1 | grep 'HTTP/1.1 200 OK') ]] || { echored "Invalid Bash VER! Check this: http://mirrors.kernel.org/gnu/bash/ for valid versions!"; usage; }
PVER=$(echo $VER | sed 's/\.//')
[ -z $ARCH ] && ARCH=arm
case $ARCH in
  arm64|aarch64) target_host=aarch64-linux-android;;
  arm) target_host=arm-linux-androideabi;;
  x86_64) target_host=x86_64-linux-android;;
  x86|i686) target_host=i686-linux-android;;
  *) echored "Invalid ARCH entered!"; usage;;
esac
[ -z $API ] && API=21
[ $API -eq $API ] || { echored "Invalid API entered. Integers only!"; usage; }

setup_bash

# Set up Android NDK
echogreen "Fetching Android NDK $NDK"
[ -f "android-ndk-$NDK-linux-x86_64.zip" ] || wget https://dl.google.com/android/repository/android-ndk-$NDK-linux-x86_64.zip
[ -d "android-ndk-$NDK" ] || unzip -o android-ndk-$NDK-linux-x86_64.zip
echogreen "Setting Up Android NDK $NDK"
python android-ndk-$NDK/build/tools/make_standalone_toolchain.py --arch $ARCH --api $API --install-dir Toolchains --force
[ $? -ne 0 ] && { echored "Error in NDK Setup!"; exit 1; }

# Add the standalone toolchain to the search path.
export PATH=$PATH:$DIR/bash_android/Toolchains/bin

# Tell configure what tools to use.
export AR=$target_host-ar
export AS=$target_host-clang
export CC=$target_host-clang
export CXX=$target_host-clang++
export LD=$target_host-ld
export STRIP=$target_host-strip

# Tell configure what flags Android requires.
export LDFLAGS="-static -s"

# Apply bash patches - Android patches originally by Alexander Gromnitsky, ATechnoHazard, koro666, and Termux @Github
apply_patches

# Configure - valid arguments found from termux-packages and bash-on-android github repos 
echogreen "Configuring"
./configure --host=$target_host --disable-nls --enable-static-link --without-bash-malloc bash_cv_dev_fd=whacky bash_cv_getcwd_malloc=yes --enable-multibyte --prefix=/system
[ $? -eq 0 ] || { echored "Configure failed!"; exit 1; }

# Build bash
echogreen "Building"
make

[ $? -eq 0 ] && { mv -f bash $DIR/bash; echogreen "Bash binary built sucessfully and can be found at: $DIR"; }