npm安装cnpm、ganache-cli、truffle等后，使用它们时提示Command not found。需添加环境变量

准备学习solidity，按照书本要求在linux上搭建环境，先后安装了nodejs、npm等
node -v

v15.8.0

npm -v

7.16.0

然后使用npm安装cnpm，执行
sudo npm install -g cnpm --registry=https://registry.npm.taobao.org
之后使用cnpm安装web3，执行
sudo cnpm install web3 -g
提示：

Command ‘cnpm’ not found

输入cnpm -v也是如此。
于是打算跳过，进行下一步用npm安装ganache-cli和truffle，执行
sudo npm install -g ganache-cli
安装后显示：

changed 6 packages in 1s

2 packages are looking for funding run ‘npm fund’ for details

执行
sudo npm install -g truffle
安装完成后提示了一些warning：

npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
npm WARN deprecated har-validator@5.1.5: this library is no longer supported
npm WARN deprecated fsevents@2.1.3: “Please update to latest v2.3 or v2.2”
npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
npm WARN deprecated debug@4.1.1: Debug versions >=3.2.0 < 3.2.7 || >=4 <4.3.1 have a low-severity ReDos regression when used in a Node.js environment. It is recommended you upgrade to 3.2.7 or 4.3.1. (https://github.com/visionmedia/debug/issues/797)
npm WARN deprecated remotedev-serialize@0.1.9: Package moved to @redux-devtools/serialize.
npm WARN deprecated redux-devtools-instrument@1.10.0: Package moved to @redux-devtools/instrument.
npm WARN deprecated redux-devtools-core@0.2.1: Package moved to @redux-devtools/app.
npm WARN deprecated mkdirp@0.5.1: Legacy versions of mkdirp are no longer supported. Please update to mkdirp 1.x. (Note that the API surface has changed to use Promises in 1.x.)
npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
npm WARN deprecated multicodec@0.5.7: stable api reached
npm WARN deprecated node-pre-gyp@0.11.0: Please upgrade to @mapbox/node-pre-gyp: the non-scoped node-pre-gyp package is deprecated and only the @mapbox scoped package will recieve updates in the future
npm WARN deprecated ethereumjs-common@1.5.2: New versions are published within new scoped package name format @ethereumjs/common. Please update.
npm WARN deprecated core-js@2.6.12: core-js@< 3.3 is no longer maintained and not recommended for usage due to the number of issues. Because of the V8 engine whims, feature detection in old core-js versions could cause a slowdown up to 100x even if nothing is polyfilled. Please, upgrade your dependencies to the actual version of core-js.

changed 886 packages in 2m

此时无法使用ganache和truffle，同样提示Command not found，怀疑是否安装成功
查看npm所有全局安装的模块，执行npm list -g：

/usr/local/node/node-v15.8.0-linux-x64/lib
├── cnpm@6.2.0
├── ethereumjs-testrpc@6.0.3
├── ganache-cli@6.12.2
├── npm@7.16.0
├── solc@0.8.4
├── truffle@5.3.9
├── web3@1.3.6
└── yarn@1.22.10

应该都已经安装成功

最终发现是未设置环境变量所致
解决方法：为当前用户永久添加环境变量

1、先要找到cnpm、truffle等的具体路径，可使用whereis命令查找，比如执行whereis truffle后显示：

truffle: /usr/local/node/node-v15.8.0-linux-x64/bin/truffle

2、编辑用户目录下的隐藏文件.bashrc（执行ls看不到，需要执行ls -a）
在用户目录下执行vim .bashrc进入编辑

在文件末尾添加export PATH="/usr/local/node/node-v15.8.0-linux-x64/bin/:$PATH"
注意：具体的path路径大家可能不同
3、保存退出后执行命令source ~/.bashrc使之生效
成功解决！