The "android" command is deprecated.
For command-line tools, use tools/bin/sdkmanager and tools/bin/avdmanager
If you do not need Android Studio, you can download the basic Android command line tools from developer.android.com in section Command line tools only.
from CLI it should be somfing like:
curl --output sdk-tools-linux.zip https://dl.google.com/android/repository/sdk-tools-linux-4333796.zip
or
wget --output-document sdk-tools-linux.zip https://dl.google.com/android/repository/sdk-tools-linux-4333796.zip
After that just unpack the archive to the target folder
unzip sdk-tools-linux.zip
And now we can install everything you need...
./tools/bin/sdkmanager --install 'build-tools;29.0.2' 'platform-tools' 'platforms;android-29' 'tools'
You can get a complete list of packages using the command ./tools/bin/sdkmanager --list
Some packages require acceptance of the license agreement. you can accept it interactively or just pass "y" to the input stream, like this(two agreements in case):
echo -ne "y\ny" | ./tools/bin/sdkmanager --install 'system-images;android-29;default;x86_64'
And of course, for your convenience, you can export variables such as ANDROID_HOME or ANDROID_SDK_ROOT (including doing it in ~/.profile or ~/.bash_profile) or patch the PATH variable - all this is at your discretion.
Script example:
mkdir /opt/android-sdk
cd /opt/android-sdk
curl --output sdk-tools-linux.zip https://dl.google.com/android/repository/sdk-tools-linux-4333796.zip
unzip sdk-tools-linux.zip
echo -ne "y" | ./tools/bin/sdkmanager --install 'build-tools;29.0.2' 'platform-tools' 'platforms;android-29' 'tools'
Requirements:
curl(or wget) and unzip
Troubleshooting:
if you see Warning: Could not create settings, you need to have the tools directory inside the cmdline-tools directory inside the ANDROID_HOME (create it if needed with this exact name) see Android Command line tools sdkmanager always shows: Warning: Could not create settings