regex-negation

来源： https://stackoverflow.com/questions/50246702/how-to-mask-credit-card-number-mask-in-a-text

问题 I wrote this regex that matches any .ts or .tsx file names but shouldn't match spec.tsx or spec.ts. Below is the regex I wrote. (?!spec)\.(ts|tsx)$ But it fails to ignore.spec.tsx and spec.ts files. What am I doing wrong here? Please advice. 回答1: The negative lookahead syntax ( (?!...) ) looks ahead from wherever it is in the regex. So your (?!spec) is being compared to what follows that point, just before the \. . In other words, it's being compared to the file extension, .ts or .tsx . The

问题 This question already has answers here : What is a regex to match ONLY an empty string? (9 answers) Closed 11 days ago . This may be a simple question to some: how do you actually match nothing using regex in R? Suppose you have a vector of strings such as this: q <- c("a", "12", "0", "", "300") And suppose further you want to match the empty string "" , how to go about this? It seems one can reasonably well match "" using grep to match the metacharacter . meaning 'any character', either as

问题 This question already has answers here : What is a regex to match ONLY an empty string? (9 answers) Closed 11 days ago . This may be a simple question to some: how do you actually match nothing using regex in R? Suppose you have a vector of strings such as this: q <- c("a", "12", "0", "", "300") And suppose further you want to match the empty string "" , how to go about this? It seems one can reasonably well match "" using grep to match the metacharacter . meaning 'any character', either as

问题 I'm trying to write a very simple regular expression that matches any file name that doesn't end in .php. I came up with the following... (.*?)(?!\.php)$ ...however this matches all filenames. If someone could point me in the right direction I'd be very grateful. 回答1: Almost: .*(?!\.php)....$ The last four dots make sure that there is something to look ahead at , when the look-ahead is checked. The outer parentheses are unnecessary since you are interested in the entire match. The reluctant .

问题 I'm trying to write a very simple regular expression that matches any file name that doesn't end in .php. I came up with the following... (.*?)(?!\.php)$ ...however this matches all filenames. If someone could point me in the right direction I'd be very grateful. 回答1: Almost: .*(?!\.php)....$ The last four dots make sure that there is something to look ahead at , when the look-ahead is checked. The outer parentheses are unnecessary since you are interested in the entire match. The reluctant .

问题 I've a code in grok, which captures messages, and if they meet a given criteria, they get a tag. My problem is, that sometimes this filter works while testing, and sometimes does not. The regexp in question is the following: ^(?!(?:\d\d\d\d-\d\d-\d\d.\d\d:\d\d:\d\d)).*$ This line checks if the given message does not begin with a given time stamp format. In other words: if the given message does not begin with this time stamp, then it gets a tag. You can test it yourself with this online

问题 I've a code in grok, which captures messages, and if they meet a given criteria, they get a tag. My problem is, that sometimes this filter works while testing, and sometimes does not. The regexp in question is the following: ^(?!(?:\d\d\d\d-\d\d-\d\d.\d\d:\d\d:\d\d)).*$ This line checks if the given message does not begin with a given time stamp format. In other words: if the given message does not begin with this time stamp, then it gets a tag. You can test it yourself with this online

问题 I've a code in grok, which captures messages, and if they meet a given criteria, they get a tag. My problem is, that sometimes this filter works while testing, and sometimes does not. The regexp in question is the following: ^(?!(?:\d\d\d\d-\d\d-\d\d.\d\d:\d\d:\d\d)).*$ This line checks if the given message does not begin with a given time stamp format. In other words: if the given message does not begin with this time stamp, then it gets a tag. You can test it yourself with this online

问题 Is it possible to write a regex pattern to match abc where each letter is not literal but means that text like xyz (but not xxy ) would be matched? I am able to get as far as (.)(?!\1) to match a in ab but then I am stumped. After getting the answer below, I was able to write a routine to generate this pattern. Using raw re patterns is much faster than converting both the pattern and a text to canonical form and then comaring them. def pat2re(p, know=None, wild=None): """return a compiled re