http://www.endmemo.com/program/R/grep.php
我在图表中查看了与空白行相对应的正则表达式，但似乎找不到它。我已经尝试过了，\\n但这意味着换行，而不一定是空白。
例如：
string = c("Precedence: bulk",
"List-Unsubscribe: <mailto:[email protected]>",
"Content-Transfer-Encoding: 7bit",
"",
"Martin A posted:",
"Tassos Papadopoulos, the Greek sculptor behind the plan, judged that the",
" Mount Athos monastic community, was ideal for the patriotic sculpture. ",
" ",
" As well as Alexander's granite features, 240 ft high and 170 ft wide, a",
"planned",
"---------------------",
"So is this mountain limestone or granite?")
因此，第4行和第8行为空，我想grep返回这些索引。
在R中，您需要转义反斜杠，所以应该这样^\\s*$。您也可以使用^[[:space:]]*$。
grepl("^[[:space:]]*$", c("", " ", "\t"))
# [1] TRUE TRUE TRUE
grep("^[[:space:]]*$", string)
# [1] 4 8
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