I am trying to extract a string matching a pattern in a string. To make sense:
我正在尝试提取匹配字符串中的模式的字符串。有意义：
x <- "this.is.fairly//Whatit.is/path/IDbeginUntilhere7/seenit"
The objective is of the regex is to return: IDbeginUntilhere. I tried this:
正则表达式的目标是返回：IDbeginUntilhere。我试过这个：
str <- regmatches(x, gregexpr("^I.*7$", x))
which I understand it doesn't work since the I is located in the middle of the string. The question may be too simple, but I'd appreciate any help I can get.
我明白它不起作用，因为我位于字符串的中间。这个问题可能太简单了，但我很感激我能得到的任何帮助。
1 个解决方案
#1
2
It is clear the main issue is the anchors: start of string ^ and end of string $.
很明显，主要问题是锚点：字符串^的开头和字符串$的结尾。
The secondary issue is the greedy dot that will also match across / delimited subparts (i.e. will match the whole Id7/Not-to-match7 instead of Id7).
次要问题是贪婪的点也将匹配跨/分隔的子部分（即将匹配整个Id7 / Not-to-match7而不是Id7）。
You need to use something like
你需要使用类似的东西
str <- regmatches(x, gregexpr("I[^/]*7", x))
See regex demo
请参阅正则表达式演示
If you do not need the 7, you need to use a look-ahead, and a Perl-like regex:
如果你不需要7，你需要使用前瞻和类似Perl的正则表达式：
str <- regmatches(x, gregexpr("I[^/]*(?=7)", x, perl=TRUE))
See another demo
看另一个演示
#1
2
It is clear the main issue is the anchors: start of string ^ and end of string $.
很明显，主要问题是锚点：字符串^的开头和字符串$的结尾。
The secondary issue is the greedy dot that will also match across / delimited subparts (i.e. will match the whole Id7/Not-to-match7 instead of Id7).
次要问题是贪婪的点也将匹配跨/分隔的子部分（即将匹配整个Id7 / Not-to-match7而不是Id7）。
You need to use something like
你需要使用类似的东西
str <- regmatches(x, gregexpr("I[^/]*7", x))
See regex demo
请参阅正则表达式演示
If you do not need the 7, you need to use a look-ahead, and a Perl-like regex:
如果你不需要7，你需要使用前瞻和类似Perl的正则表达式：
str <- regmatches(x, gregexpr("I[^/]*(?=7)", x, perl=TRUE))
See another demo
看另一个演示