bash 是否可以仅在尚未安装 npm 包的情况下才安装它？
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Is it possible to install npm package only if it has not been already installed?
提问by kovpack
Is it possible to install npmpackage only if it has not been already installed?
是否可以npm仅在尚未安装的情况下安装软件包？
I need this to speed up test on CircleCI, but when I run npm install [email protected]etc. it always downloads things and installs them from scracth, however, node_modulesfolder with all modules is already present at the moment of running commands (cached from previous build) and protractor --versionetc. shows the needed version of the package.
我需要这个来加速 CircleCI 上的测试，但是当我运行npm install [email protected]等时，它总是从 scracth 下载东西并安装它们，但是，node_modules在运行命令（从以前的构建中缓存）protractor --version等时，所有模块的文件夹已经存在。显示所需的软件包版本。
Its perfect to have some one-line command like this:
有一些这样的单行命令是完美的：
protractor --version || npm install -g [email protected]
but the one that will also check version of the package.
但也将检查包的版本。
采纳答案by Jerome WAGNER
with bash you can do
使用 bash 你可以做到
[ $(node -p "require('protractor/package.json').version") != "2.1.0" ] && npm install [email protected]
回答by An Nguyen
You could try npm list protractor || npm install [email protected]
你可以试试 npm list protractor || npm install [email protected]
Where npm list protractoris used to find protractorpackage.
wherenpm list protractor用于查找protractor包。
If the package is not found, it will return npm ERR! code 1and do npm install [email protected]for installation
如果没有找到包，它将返回npm ERR! code 1并npm install [email protected]进行安装
回答by bishop
Function version of the excellent answer by @JeromeWAGNER:
@JeromeWAGNER的优秀答案的功能版本：
function install_package_if_needed() {
local p=${1:-Package required}
local v=${2:-Version required}
shift 2
local i=$(node -p "require('$p/package.json').version" 2>/dev/null)
[ "$i" == "$v" ] || npm "$@" install "$p@$v"
}
Use like:
像这样使用：
$ install_package_if_needed protractor 2.1.0
To pass additional options to npm, specify them after the version, like so:
要将其他选项传递给npm，请在版本之后指定它们，如下所示：
$ install_package_if_needed protractor 2.1.0 -g
回答by theJC
[ $(node -p "try{require('protractor/package.json').version}catch(e){}") != "2.1.0" ] && npm install grunt
回答by sthames42
I had this same issue together with wanting to install global dependencies from any "package.json" file requiring them.
我有同样的问题，希望从任何需要它们的“package.json”文件安装全局依赖项。
This is for a Windows development environment.
这是针对 Windows 开发环境的。
