调用系统命令并将变量作为参数传递给管道 [英] Invoke a system command and pipe a variable as an argument

问题描述

我正在尝试使用 system2 函数传递系统命令，但我想将变量作为参数传递给该函数.

I'm trying to pass a system command, using the system2 function, but I want to pass a variable as an argument to the function.

更具体地说，我有一个bash命令 xml-to-json ，我想从R上运行一个包含XML的对象.

More specifically I have a bash command, xml-to-json, that I want to run from R on an object containing XML.

我可以将此数据写入文件，然后第二次运行 system2 ，但是我想尽可能地简化.

I could write this data to file and then run system2 a second time, but I'd like to keep this as parsimonious as possible.

推荐答案

system2 的 input 自变量可以满足您的要求:

The input argument to system2 does what you want:

输入:如果提供了字符向量，则将其复制一个字符串每行到一个临时文件，以及标准输入命令"被重定向到文件.

input: if a character vector is supplied, this is copied one string per line to a temporary file, and the standard input of ‘command’ is redirected to the file.

示例:

foo = c("foo", "bar")
result = system2("cat", input = foo, stdout = TRUE)

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