近期在研究bitcoin比特币，想将所有地址的余额（UTXO）导出来。
网上找了一下，找到了这个开源库：btcposbal2csv
https://github.com/graymauser/btcposbal2csv
这个库是python写的，它依赖一个第三方组件plyvel。plyvel提供了操作leveldb的接口。按作者的说明，安装是很简单的，就是
代码语言：javascript复制> pip install plyvel安装完后，运行：
代码语言：javascript复制> python btcposbal2csv.py然后就抛错了：
代码语言：javascript复制Traceback (most recent call last):
File "btcposbal2csv.py", line 5, in <module>
from utils import parse_ldb
File "/Users/zhangsan/Desktop/bitcoin-research/btcposbal2csv/utils.py", line 3, in <module>
import plyvel
File "/Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/__init__.py", line 6, in <module>
from ._plyvel import ( # noqa
ImportError: dlopen(/Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/_plyvel.so, 2): Symbol not found: __ZTIN7leveldb10ComparatorE
Referenced from: /Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/_plyvel.so
Expected in: /usr/local/opt/leveldb/lib/libleveldb.1.dylib
in /Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/_plyvel.so错误是Symbol not found: __ZTIN7leveldb10ComparatorE
就是有个方法找不到了，反复折腾重装了pip、python、leveldb和plyvel后，并用nm命令查看了.dylib、.so里用的方法后，突然搞明白了原因，leveldb近期升级到了1.23版本，去掉了一些旧方法，而plyvel版本没更新仍依赖这些旧方法。
搞明白了原因，接下来就是要安装leveldb的旧版本了。
mac下安装leveldb的旧版本有两种方法，一种是直接下载对应版本的源码包，自己make。另一种是用brew来安装。
为了便于系统管理软件，我决定用brew来安装旧版的leveldb。
网上找到的一般方法是用brew info来查看包地址，然后在git里查找对应的历史记录，执行`brew install 记录地址`来安装：
代码语言：javascript复制> brew info leveldb
leveldb: stable 1.23 (bottled)
Key-value storage library with ordered mapping
https://github.com/google/leveldb/
/usr/local/Cellar/leveldb/1.23 (31 files, 879.8KB) *
Poured from bottle on 2021-04-20 at 19:17:56
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/leveldb.rb
License: BSD-3-Clause
==> Dependencies
Build: cmake ✔
Required: gperftools ✔, snappy ✔
==> Analytics
install: 1,657 (30 days), 5,164 (90 days), 14,479 (365 days)
install-on-request: 1,422 (30 days), 4,381 (90 days), 12,358 (365 days)
build-error: 0 (30 days)在浏览器打开 https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/leveldb.rb
点History，找到对应的版本，例如我的目标版本是1.21，点今后去选择View，最后点Raw，得到下面的url
https://raw.githubusercontent.com/Homebrew/homebrew-core/75277166a28d6a948b045d18e94e1832761d2974/Formula/leveldb.rb
最后执行下面命令来安装：
代码语言：javascript复制> brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/75277166a28d6a948b045d18e94e1832761d2974/Formula/leveldb.rb却再次抛错：
代码语言：javascript复制> brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/1478ac3410e452961f8a9c9640716542f6acd710/Formula/leveldb.rb
Traceback (most recent call last):
9: from /usr/local/Homebrew/Library/Homebrew/brew.rb:122:in `<main>'
8: from /usr/local/Homebrew/Library/Homebrew/cmd/install.rb:131:in `install'
7: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:303:in `parse'
6: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:634:in `formulae'
5: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:634:in `map'
4: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:638:in `block in formulae'
3: from /usr/local/Homebrew/Library/Homebrew/formulary.rb:374:in `factory'
2: from /usr/local/Homebrew/Library/Homebrew/formulary.rb:155:in `get_formula'
1: from /usr/local/Homebrew/Library/Homebrew/formulary.rb:159:in `klass'
/usr/local/Homebrew/Library/Homebrew/formulary.rb:250:in `load_file': Invalid usage: Installation of leveldb from a GitHub commit URL is unsupported! `brew extract leveldb` to a stable tap on GitHub instead. (UsageError)
12: from /usr/local/Homebrew/Library/Homebrew/brew.rb:155:in `<main>'
11: from /usr/local/Homebrew/Library/Homebrew/brew.rb:157:in `rescue in <main>'
10: from /usr/local/Homebrew/Library/Homebrew/help.rb:64:in `help'
9: from /usr/local/Homebrew/Library/Homebrew/help.rb:83:in `command_help'
8: from /usr/local/Homebrew/Library/Homebrew/help.rb:103:in `parser_help'
7: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:303:in `parse'
6: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:634:in `formulae'
5: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:634:in `map'
4: from /usr/local/Homebrew/Library/Homebrew/cli/parser.rb:638:in `block in formulae'
3: from /usr/local/Homebrew/Library/Homebrew/formulary.rb:374:in `factory'
2: from /usr/local/Homebrew/Library/Homebrew/formulary.rb:155:in `get_formula'
1: from /usr/local/Homebrew/Library/Homebrew/formulary.rb:159:in `klass'
/usr/local/Homebrew/Library/Homebrew/formulary.rb:250:in `load_file': Invalid usage: Installation of leveldb from a GitHub commit URL is unsupported! `brew extract leveldb` to a stable tap on GitHub instead. (UsageError)我在stackoverflow里找到了答案，MAC新版已经禁止直接通过url这种方式来安装指定版本软件了。现在必须通过brew extract命令来安装。
命令如下：
代码语言：javascript复制#下载指定版本的安装包，存到cask
> brew extract --version=1.21 leveldb homebrew/cask运行完毕后，会提示你文件会保存到了/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask/Formula/leveldb@1.21.rb
现在可以正式安装了：
代码语言：javascript复制> brew install /usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask/Formula/leveldb@1.21.rb现在终于安装好leveldb了，别忘了重装一下plyvel：
代码语言：javascript复制> pip uninstall plyvel
> pip install plyvel再来运行一下试试：
代码语言：javascript复制> python btcposbal2csv.py
Traceback (most recent call last):
File "btcposbal2csv.py", line 5, in <module>
from utils import parse_ldb
File "/Users/zhangsan/Desktop/bitcoin-research/btcposbal2csv/utils.py", line 3, in <module>
import plyvel
File "/Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/__init__.py", line 6, in <module>
from ._plyvel import ( # noqa
ImportError: dlopen(/Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/_plyvel.so, 2): Library not loaded: /usr/local/opt/leveldb/lib/libleveldb.1.dylib
Referenced from: /Users/zhangsan/Library/Python/2.7/lib/python/site-packages/plyvel/_plyvel.so
Reason: image not found为啥会Library not loaded:/usr/local/opt/leveldb/lib/libleveldb.1.dylib呢？
进目录看一下，发现原来指定版本安装的情况下，安装目录变成了 /usr/local/opt/leveldb@1.21
我们建个软链就行了：
代码语言：javascript复制> ln -s /usr/local/opt/leveldb@1.21 /usr/local/opt/leveldb最后运行命令来做我们最初的目标：
代码语言：javascript复制python btcposbal2csv.py --lowmem --keep_sqlite="./balance.db" /Users/zhangsan/Desktop/Bitcoin-data/chainstate /Users/zhangsan/Desktop/addresses_with_balance.csv这下终于没有报错了，终于可以愉快的将bitcoin的所有地址的余额导出来了！
【相关参考】
https://stackoverflow.com/questions/3987683/homebrew-install-specific-version-of-formula
https://www.cnblogs.com/nnylee/p/13379617.html
