从R中的底层C函数中抑制消息

/* =========
 * Printing:
 * =========
 *
 * All printing in R is done via the functions Rprintf and REprintf
 * or their (v) versions Rvprintf and REvprintf.
 * These routines work exactly like (v)printf(3).  Rprintf writes to
 * ``standard output''.  It is redirected by the sink() function,* and is suitable for ordinary output.  REprintf writes to
 * ``standard error'' and is useful for error messages and warnings.
 * It is not redirected by sink().

但是,我们可以使用type =“message”来处理这个问题;来自help(“capture.output”)：

Messages sent to stderr() (including those from message,warning and
stop) are captured by type = “message”. Note that this can be “unsafe” and should only be used with care.

首先,我使用您正在处理的相同行为创建一个C函数：

#include <Rcpp.h>
using namespace Rcpp;

// [[Rcpp::export]]
NumericVector example_function(NumericVector x) {
    REprintf("CPLEX environment openedn");
    REprintf("Closed CPLEX environmentn");
    // As mentioned by Dirk Eddelbuettel in the comments,// Rcpp::Rcerr goes into the same REprintf() stream:
    Rcerr << "Some more stuffn";
    return x;
}

如果我通常从R调用它,我得到：

example_function(42)

CPLEX environment opened
Closed CPLEX environment
Some more stuff
[1] 42

但是,我可以这样做：

invisible(capture.output(example_function(42),type = "message"))

[1] 42

虽然输出打印到控制台,但消息却没有.

警告

如果我没有提到上面引用的帮助文件中的警告,我会失职：

Note that this can be “unsafe” and should only be used with care.

原因是这将消除实际错误的所有输出.考虑以下：

> log("A")
Error in log("A") : non-numeric argument to mathematical function
> invisible(capture.output(log("A"),type = "message"))
>

因此,您可能希望或不希望将捕获的输出发送到文本文件,以防您必须诊断出错的地方.例如：

invisible(capture.output(log("A"),type = "message",file = "example.txt"))

然后我不必在控制台中看到消息,但如果我之后需要检查example.txt,那么消息就在那里：

Error in log("A") : non-numeric argument to mathematical function