conan入门(三十一):在命令行(shell)中从profile中读取配置参数

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最近使用conan来执行本地或交叉编译时，我发现我需要知道当前profile定义的编译器的类型和版本以及平台，希望用profile中定义的os,arch,compier生成安装路径名如windows-msvc-x86_64，该怎么实现呢？

conan profile show

基本的思路就是用 conan profile show命令获取profile中的配置参数,（参见 https://docs.conan.io/2/reference/commands/profile.html，
执行 conan profile show --format=json可以以json 格式输出当前profile（host及build)中定义所有的参数
如下：

{"host": {"settings": {"arch": "x86_64","build_type": "Release","compiler": "gcc","compiler.cppstd": "gnu11","compiler.libcxx": "libstdc++11","compiler.version": "5.2","os": "Windows"},"package_settings": {},"options": {"boost/*:without_stacktrace": "True"},"tool_requires": {},"conf": {},"build_env": ""},"build": {"settings": {"arch": "x86_64","build_type": "Release","compiler": "gcc","compiler.cppstd": "gnu11","compiler.libcxx": "libstdc++11","compiler.version": "5.2","os": "Windows"},"package_settings": {},"options": {"boost/*:without_stacktrace": "True"},"tool_requires": {},"conf": {},"build_env": ""}
}

有了这个json,就可以用python的json工具来读取其中的内容了

示例一

如下命令读取host profile的编译类型字段(host.settings.compiler)

conan profile show --format=json | python -c "import sys, json; print(json.load(sys.stdin)['host']['settings']['compiler'])"

输出

gcc

示例二

如下读取compiler,arch,os字段拼写生成完整的类machine描述

conan profile show --format=json | python -c "import sys, json; j=json.load(sys.stdin)['host']['settings'];m=j['os']+'-'+j['compiler']+'-'+j['arch']; print(m.lower())"

输出