This script can be used for building multiple react-native apps from a single git repo.

scriptAndroid.sh

#!/bin/bash
# MUSTAFA ILKER SARAC
# This script can be used for building multiple react-native apps from a single git repo.
# It needs master files for the default configurations.
# master files are generally the copy of the current config files of that git repo.
# If current state of the app changes i.e. adding new 3rd party components so package.json changes;
# then one should be responsible to reflect these changes to the master files to be synced with the current state of the repo.
# This script can be used to alter the current state, so that new apps could be generated with new names etc.
# scriptAndroid.sh
# "chmod +x ./scriptAndroid" to make script executable.
# ls -al
# -rwxr-xr-x    1 milkers  staff   6569 Jan 11 14:35 scriptAndroid.


if [ $# != 2 ]
then
    echo "**************************************"
    echo "This script works with 2 parameters."
    echo "./scriptAndroid environment app_name"
    echo "environment params: dev, test, prod."
    echo "app_name params   : APP1, APP2, APP3, APP4."
    echo "**************************************"
    echo "Ex-1:"
    echo "./scriptAndroid dev APP1"
    echo "./scriptAndroid dev APP2"
    echo "./scriptAndroid dev APP3"
    echo "./scriptAndroid dev APP4"
    echo "**************************************"
    echo "Ex-2:"
    echo "./scriptAndroid test APP1"
    echo "./scriptAndroid test APP2"
    echo "./scriptAndroid test APP3"
    echo "./scriptAndroid test APP4"
    echo "**************************************"
    echo "Ex-3:"
    echo "./scriptAndroid prod APP2"
    exit -1
elif [ $1 != "dev" ] && [ $1 != "test" ] && [ $1 != "prod" ]
then
    echo "First param (environment) could be either \"dev, test, prod\" "
    exit -1
elif [ $2 != "APP1" ] && [ $2 != "APP2" ] && [ $2 != "APP3" ] && [ $2 != "APP4" ]
then
    echo "Second param (app_name) could be either \"APP1, APP2, APP3, APP4\" "
    exit -1
fi

lcAppName="" # lower case app name
if [ $2 = "APP1" ]
then
	lcAppName="app1"
elif [ $2 = "APP2" ]
then
	lcAppName="app2"
elif [ $2 = "APP3" ]
then
	lcAppName="app3"
elif [ $2 = "APP4" ]
then
	lcAppName="app4"
fi


echo "1) Copy configuration files."
# copy gradle-wrapper.properties
rm -rf ./android/gradle/wrapper/gradle-wrapper.properties
cp -r ./_configFiles/androidMasterFiles/gradle-wrapper.properties ./android/gradle/wrapper/gradle-wrapper.properties

# copy android_build.gradle over android/build.gradle
rm -rf ./android/build.gradle
cp -r ./_configFiles/androidMasterFiles/android_build.gradle ./android/build.gradle

# copy app_build.gradle over android/app/build.gradle and update applicationId
rm -rf ./android/app/build.gradle
cp -r ./_configFiles/androidMasterFiles/app_build.gradle ./android/app/build.gradle
sed -i bckp -e "s/com.bbn.bbn_app1dev/com.bbn.$lcAppName$1/g" ./android/app/build.gradle
rm -rf ./android/app/build.gradlebckp

# create a correct path for MainApplication.java and MainActivity.java.
rm -rf ./android/app/src/main/java/com/*
mkdir -p ./android/app/src/main/java/com/bbn/$lcAppName$1/
cp -r ./_configFiles/androidMasterFiles/MainActivity.java ./android/app/src/main/java/com/bbn/$lcAppName$1/MainActivity.java
cp -r ./_configFiles/androidMasterFiles/MainApplication.java ./android/app/src/main/java/com/bbn/$lcAppName$1/MainApplication.java
sed -i bckp -e "s/com.bbn.bbn_app1dev/com.bbn.$lcAppName$1/g" ./android/app/src/main/java/com/bbn/$lcAppName$1/MainActivity.java
sed -i bckp -e "s/com.bbn.bbn_app1dev/com.bbn.$lcAppName$1/g" ./android/app/src/main/java/com/bbn/$lcAppName$1/MainApplication.java
rm -rf ./android/app/src/main/java/com/bbn/$lcAppName$1/MainActivity.javabckp
rm -rf ./android/app/src/main/java/com/bbn/$lcAppName$1/MainApplication.javabckp

# copy AndroidManifest.xml file and update its content.
rm -rf ./android/app/src/main/AndroidManifest.xml
cp -r ./_configFiles/androidMasterFiles/AndroidManifest.xml ./android/app/src/main/AndroidManifest.xml
sed -i bckp -e "s/com.bbn.bbn_app1dev/com.bbn.$lcAppName$1/g" ./android/app/src/main/AndroidManifest.xml
if [ $1 = "prod" ]
then
	sed -i bckp -e "s/bbn-APP1-dev/bbn-$2/g" ./android/app/src/main/AndroidManifest.xml
else
	sed -i bckp -e "s/bbn-APP1-dev/bbn-$2-$1/g" ./android/app/src/main/AndroidManifest.xml
fi
rm -rf ./android/app/src/main/AndroidManifest.xmlbckp

# update app name on strings.xml
rm -rf ./android/app/src/main/res/values/strings.xml
cp -r ./_configFiles/androidMasterFiles/strings.xml ./android/app/src/main/res/values/strings.xml
if [ $1 = "prod" ]
then
	sed -i bckp -e "s/APP1dev/$2/g" ./android/app/src/main/res/values/strings.xml
else
	sed -i bckp -e "s/APP1dev/$2$1/g" ./android/app/src/main/res/values/strings.xml
fi
rm -rf ./android/app/src/main/res/values/strings.xmlbckp

# copy proguard file in order to obfuscate on release mode.
rm -rf ./android/app/proguard-rules.pro
cp -r ./_configFiles/androidMasterFiles/proguard-rules.pro ./android/app/proguard-rules.pro

# copy Avenir font to assets.
cp -r ./images/fonts/Avenir.ttf ./android/app/src/main/assets/fonts/Avenir.ttf

# copy .cer file to assets for pinch module.
cp -r ./_configFiles/gd-class2-root.cer ./android/app/src/main/assets/gd-class2-root.cer

# copy launcher icons.
cp -r ./_configFiles/androidMasterFiles/androidLauncherIcon/$lcAppName-mdpi/ic_launcher_app.png ./android/app/src/main/res/mipmap-mdpi/ic_launcher_app.png
cp -r ./_configFiles/androidMasterFiles/androidLauncherIcon/$lcAppName-hdpi/ic_launcher_app.png ./android/app/src/main/res/mipmap-hdpi/ic_launcher_app.png
cp -r ./_configFiles/androidMasterFiles/androidLauncherIcon/$lcAppName-xhdpi/ic_launcher_app.png ./android/app/src/main/res/mipmap-xhdpi/ic_launcher_app.png
cp -r ./_configFiles/androidMasterFiles/androidLauncherIcon/$lcAppName-xxhdpi/ic_launcher_app.png ./android/app/src/main/res/mipmap-xxhdpi/ic_launcher_app.png


# Styles are arranged in a similar way but excluded because of not being generic enough,
# to solve problems of the most.


echo "2) Create Debug and Release .apk files."
# If you plan to release, delete the 'drawable' folders, they create problem while producing .apk for release.
rm -rf ./android/app/src/main/res/drawable-*
(cd android/ && ./gradlew assembleRelease) # be sure to put .keystore file under /app folder.
#(cd android/ && ./gradlew assembleDebug)


# copy images to the assests folder for 'debug' case => (cd android/ && ./gradlew assembleDebug)
# Use this if you want to call 'react-native run-android' instead of './gradlew installDebug'.
# Problems might occure. https://github.com/facebook/react-native/issues/5787
# This is important to save image files to assests during debug release.
react-native bundle --platform android --entry-file index.android.js --bundle-output android/app/src/main/assets/index.android.bundle --dev false --reset-cache --assets-dest android/app/src/main/res/



# If you have a device connected, you can install the release/debug version of the app using;
# (cd android/ && ./gradlew installRelease)
# (cd android/ && ./gradlew installDebug)


echo "3) Please check these configurated files;"
echo "AndroidManifest.xml"
echo "app/build.gradle"
echo "MainActivity.java"
echo "MainApplication.java"
echo "proguard-rules.pro"
echo "strings.xml"
echo ""
echo ".apk files are at android/app/build/outputs."
echo "BYE"

Thanks for sharing this!
Do you have one for iOS too?