For anyone meaning to do this more reliably for different Minecraft versions, I have a Python script (adapted from parts of minecraft-launcher-lib) that does the job very nicely
Besides setting some basic variables near the top after the functions, it calls a get_classpath function that reads for example ~/.minecraft/versions/1.16.5/1.16.5.json, and loops over the property libraries array, checking to see if each object (within the array), is supposed to be added to the classpath (cp variable). whether this library is added to the java classpath is governed by the should_use_library function, deterministic based on the computer's architecture and operating system. finally, some jarfiles that are platform specific have extra things prepended to them (ex. natives-linux in org/lwjgl/lwjgl/3.2.1/lwjgl-3.2.1-natives-linux.jar). this extra prepended string is handled by get_natives_string and is empty if it doesn't apply to the current library
tested on Linux, distribution Arch Linux
#!/usr/bin/env python3
import json
import os
import platform
from pathlib import Path
import subprocess
"""
Debug output
"""
def debug(str):
if os.getenv('DEBUG') != None:
print(str)
"""
[Gets the natives_string toprepend to the jar if it exists. If there is nothing native specific, returns and empty string]
"""
def get_natives_string(lib):
arch = ""
if platform.architecture()[0] == "64bit":
arch = "64"
elif platform.architecture()[0] == "32bit":
arch = "32"
else:
raise Exception("Architecture not supported")
nativesFile=""
if not "natives" in lib:
return nativesFile
if "windows" in lib["natives"] and platform.system() == 'Windows':
nativesFile = lib["natives"]["windows"].replace("${arch}", arch)
elif "osx" in lib["natives"] and platform.system() == 'Darwin':
nativesFile = lib["natives"]["osx"].replace("${arch}", arch)
elif "linux" in lib["natives"] and platform.system() == "Linux":
nativesFile = lib["natives"]["linux"].replace("${arch}", arch)
else:
raise Exception("Platform not supported")
return nativesFile
"""
[Parses "rule" subpropery of library object, testing to see if should be included]
"""
def should_use_library(lib):
def rule_says_yes(rule):
useLib = None
if rule["action"] == "allow":
useLib = False
elif rule["action"] == "disallow":
useLib = True
if "os" in rule:
for key, value in rule["os"].items():
os = platform.system()
if key == "name":
if value == "windows" and os != 'Windows':
return useLib
elif value == "osx" and os != 'Darwin':
return useLib
elif value == "linux" and os != 'Linux':
return useLib
elif key == "arch":
if value == "x86" and platform.architecture()[0] != "32bit":
return useLib
return not useLib
if not "rules" in lib:
return True
shouldUseLibrary = False
for i in lib["rules"]:
if rule_says_yes(i):
return True
return shouldUseLibrary
"""
[Get string of all libraries to add to java classpath]
"""
def get_classpath(lib, mcDir):
cp = []
for i in lib["libraries"]:
if not should_use_library(i):
continue
libDomain, libName, libVersion = i["name"].split(":")
jarPath = os.path.join(mcDir, "libraries", *
libDomain.split('.'), libName, libVersion)
native = get_natives_string(i)
jarFile = libName + "-" + libVersion + ".jar"
if native != "":
jarFile = libName + "-" + libVersion + "-" + native + ".jar"
cp.append(os.path.join(jarPath, jarFile))
cp.append(os.path.join(mcDir, "versions", lib["id"], f'{lib["id"]}.jar'))
return os.pathsep.join(cp)
version = '1.16.5'
username = '{username}'
uuid = '{uuid}'
accessToken = '{token}'
mcDir = os.path.join(os.getenv('HOME'), '.minecraft')
nativesDir = os.path.join(os.getenv('HOME'), 'versions', version, 'natives')
clientJson = json.loads(
Path(os.path.join(mcDir, 'versions', version, f'{version}.json')).read_text())
classPath = get_classpath(clientJson, mcDir)
mainClass = clientJson['mainClass']
versionType = clientJson['type']
assetIndex = clientJson['assetIndex']['id']
debug(classPath)
debug(mainClass)
debug(versionType)
debug(assetIndex)
subprocess.call([
'/usr/bin/java',
f'-Djava.library.path={nativesDir}',
'-Dminecraft.launcher.brand=custom-launcher',
'-Dminecraft.launcher.version=2.1',
'-cp',
classPath,
'net.minecraft.client.main.Main',
'--username',
username,
'--version',
version,
'--gameDir',
mcDir,
'--assetsDir',
os.path.join(mcDir, 'assets'),
'--assetIndex',
assetIndex,
'--uuid',
uuid,
'--accessToken',
accessToken,
'--userType',
'mojang',
'--versionType',
'release'
])
