会网站建设如何找工作,互联网营销行业,自己做网站怎么跳过备案,电子商务网站软件建设核心文章目录1. 查找第一个匹配的2. 查找所有结果3. 打印匹配结果的上下文4. 使用子表达式5. 查找并替换注意: .#xff08;点#xff09;在括号中没有特殊含义#xff0c;无需转义用\转义。 1. 查找第一个匹配的
#include iostream
#include regexusing names…
文章目录1. 查找第一个匹配的2. 查找所有结果3. 打印匹配结果的上下文4. 使用子表达式5. 查找并替换注意: .点在括号中没有特殊含义无需转义用\转义。 1. 查找第一个匹配的
#include iostream
#include regexusing namespace std;int main(void)
{string pattern [^c]ei;pattern [[:alpha:]]* pattern [[:alpha:]]*;regex policy(pattern); string text receipt freind theif receive;smatch results;if(regex_search(text, results, policy))cout results.str() endl;
}输出结果
freind2. 查找所有结果
#include iostream
#include regexusing namespace std;int main (void)
{string pattern [^c]ei;pattern [[:alpha:]]* pattern [[:alpha:]]*;// 忽略大小写regex policy (pattern, regex::icase);string text receipt freind theif receive;for (sregex_iterator it (text.begin(), text.end(), policy), end_it;it ! end_it; it)cout it-str() endl;
}其中比较难理解的是sregex_iterator it (text.begin(), text.end(), policy), end_it这行代码是定义了it迭代器来进行遍历查询end_it为空sregex_iterator起到尾后迭代器的作用。
输出结果
freind
theif3. 打印匹配结果的上下文
#include iostream
#include regexusing namespace std;string text Once there were two mice. They were friends. One mouse lived in the country; the other mouse lived in the city.After many years the Country mouse saw the City mouse;he said, \Do come and see me at my house in the country.\ So the City mouse went. The City mouse said, \This foodis not good, and your house is not good. Why do you live in a hole in the field? You should come and live in the city. You would live in a nice house made of stone. You would have nice food to eat. You must come and see me atmy house in the city.\The Country mouse went to the houseof the City mouse. It was a very good house. Nice food was set ready for them to eat. But just as they began toeat they heard a great noise. The City mouse cried, \ Run! Run! The cat is coming!\ They ran away quickly and hid.After some time they came out. When they came out, the Country mouse said, \I do not like living in the city.I like living in my hole in the field. For it is nicerto be poor and happy, than to be rich and afraid.;int main (void)
{string pattern you;pattern [[:alpha:]]* pattern [[:alpha:]]*;regex policy (pattern, regex::icase);for (sregex_iterator it (text.begin(), text.end(), policy), end_it;it ! end_it ; it) {auto pos it-prefix().length();pos pos 40 ? pos - 40 : 0;cout it-prefix().str().substr (pos) \n\t\t it-str() \n it-suffix().str().substr (0, 40) endl;}}输出结果 mouse said, This foodis not good, and your house is not good. Why do you live in ahouse is not good. Why do you live in a hole in the field? You shouldlive in a hole in the field? You should come and live in the city. You wshould come and live in the city. You would live in a nice house made of ston
uld live in a nice house made of stone. You would have nice food to eat. You must cwould have nice food to eat. You must come and see me atmy house in the 4. 使用子表达式
#include iostream
#include regexusing namespace std;string text Once there were two mice. They were friends. One mouse lived in the country; the other mouse lived in the city.After many years the Country mouse saw the City mouse;he said, \Do come and see me at my house in the country.\ So the City mouse went. The City mouse said, \This foodis not good, and your house is not good. Why do you live in a hole in the field? You should come and live in the city. You would live in a nice house made of stone. You would have nice food to eat. You must come and see me atmy house in the city.\The Country mouse went to the houseof the City mouse. It was a very good house. Nice food was set ready for them to eat. But just as they began toeat they heard a great noise. The City mouse cried, \ Run! Run! The cat is coming!\ They ran away quickly and hid.After some time they came out. When they came out, the Country mouse said, \I do not like living in the city.I like living in my hole in the field. For it is nicerto be poor and happy, than to be rich and afraid.;int main (void)
{string pattern ! The (.*?)(coming)[[:alnum:]]*;regex policy (pattern);for (sregex_iterator it (text.begin(), text.end(), policy), end_it; it ! end_it ; it) {cout 总表达式\n\t it-str() \n;if ( (*it) [1].matched)cout 第1个子表达式\n\t it-str (1) \n;if ( (*it) [2].matched)cout 第2个子表达式\n\t it-str (2);}}输出结果
总表达式! The cat is coming
第1个子表达式cat is
第2个子表达式coming5. 查找并替换
regex_replace()用于查找并替换
#include iostream
#include regex
#include sstreamusing namespace std;static const string text morgan (201) 555-2368 862-555-0123\ndrew (973)555.0130\nlee (609) 555-0132 2015550175 800.555-0000;
int main (void)
{string phone_pattern (\\()? //可选左括号(\\d{3}) //区号(\\))? //可选右括号([-. ])? //可选分隔符(\\d{3}) //前三位([-. ])? //可选分隔符(\\d{4}); //后四位regex policy (phone_pattern);string format $2.$5.$7;//格式为 xxx.xxx.xxxxistringstream input (text);string line;while (getline (input, line)) {cout regex_replace (line, policy, format) endl;}
}运行结果
morgan 201.555.2368 862.555.0123
drew 973.555.0130
lee 609.555.0132 201.555.0175 800.555.0000其中format中的$n表示第n个子表达式。
默认情况下regex_replace会输出整个输入序列。 未与正则表达式匹配的部分会原样输出匹配的部分按照格式字符来输出。 如果只想要匹配的部分我们可以通过添加format_no_copy标志
string fmt $2.$5.$7
cout regex_replace (line, policy, format, regex_constants::format_no_copy) endl;此时输出结果
201.555.2368 862.555.0123
973.555.0130
609.555.0132 201.555.0175 800.555.0000 标准库定义了用来在替换过程中控制匹配或格式的标志。这些标志可以传递给函数regex_search或regex_match或是类smatch的format成员例如format_no_copy是类型match_flag_type的值定义在命名空间std::regex_constants中。 匹配标志定义在regex_constants::mat_flag_type中
match_default等价于format_defaultmatch_not_bol不将首字符作为行首处理match_not_eol不将尾字符作为行尾处理match_not_bow不将首字符作为单词首处理match_not_eow不将尾字符作为单词尾处理match_any如果存在多于一个匹配则可返回任意一个匹配match_not_null不匹配任何空序列match_continuous匹配必须从输入的首字符开始match_prev_avail输入序列包含第一个匹配之前的内容format_default用ECMAScript规则替换字符串format_sed用POSIX sed规则替换字符串format_no_copy不输出输入序列中未匹配的部分format_first_only只替换子表达式的第一次出现
参考书籍 C Primer 5 中文版
