Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "back up code"; final String string = "//9-digits phone number\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " int n;\n" + " string s;\n" + " cin >> n;\n" + " getline(cin,s);\n" + " while(n--){\n" + " regex phone10(\"09[0-9]{2}(\\\\.[0-9]{3}){2}\");\n" + " string st;\n" + " getline(cin, st);\n" + " if(regex_match(st, phone10))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n" + "//11 digits phone number\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex phone10(\"01[0-9]{9}\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, phone10))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n" + "//alphabet string\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex pattern(\"[a-zA-Z\\\\s]+\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, pattern))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n" + "//Alpha-numberic Strings With Limited Length\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex pattern(\"[a-z0-9]{6,20}\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, pattern))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n" + "//bound checking for a Product\n" + "#include <stdio.h>\n" + "#include <stdlib.h>\n" + "#include <limits.h>\n\n" + "int main()\n" + "{\n" + " unsigned int a,b;\n" + " scanf(\"%u%u\",&a,&b);\n" + " if(a!=0 && b!=0 && UINT_MAX/a<b)\n" + " printf(\"No\");\n" + " else\n" + " printf(\"Yes\");\n" + "}\n\n\n\n" + "//bound checking for a Signed Product\n" + "#include <stdio.h>\n" + "#include <stdlib.h>\n" + "#include <limits.h>\n\n" + "int main()\n" + "{\n" + " int a,b;\n" + " scanf(\"%d%d\",&a,&b);\n" + " if(a>0&&b>0){\n" + " if(INT_MAX/a<b)\n" + " printf(\"No\");\n" + " else\n" + " printf(\"Yes\");\n" + " }\n" + " else if(a<0&&b<0){\n" + " if(INT_MAX/b>a)\n" + " printf(\"No\");\n" + " else\n" + " printf(\"Yes\");\n" + " }\n" + " else if(a>0&&b<0){\n" + " if(INT_MIN/a>b)\n" + " printf(\"No\");\n" + " else\n" + " printf(\"Yes\");\n" + " }\n" + " else if(a<0&&b>0){\n" + " if(INT_MIN/b>a)\n" + " printf(\"No\");\n" + " else\n" + " printf(\"Yes\");\n" + " }\n" + " else\n" + " printf(\"Yes\");\n\n" + "}\n\n\n\n" + "//bound checking for a Signed sum\n" + "#include <stdio.h>\n" + "#include <stdlib.h>\n" + "#include <limits.h>\n\n" + "int main()\n" + "{\n" + " int a,b;\n" + " scanf(\"%d%d\",&a,&b);\n" + " if(a>0 && b>0 && b>INT_MAX-a)\n" + " printf(\"No\");\n" + " else if(a<0 && b<0 && b<INT_MIN-a)\n" + " printf(\"No\");\n" + " else\n" + " printf(\"Yes\");\n" + "}\n\n\n\n" + "//Bound checking for a Sum\n" + "#include <stdio.h>\n" + "#include <stdlib.h>\n" + "#include <limits.h>\n\n" + "int main()\n" + "{\n" + " unsigned int a,b;\n" + " scanf(\"%u%u\",&a,&b);\n" + " if(UINT_MAX-a>=b)\n" + " printf(\"Yes\");\n" + " else\n" + " printf(\"No\");\n" + "}\n\n\n" + "//bound checking for an Integer\n" + "#include <stdio.h>\n" + "#include <stdlib.h>\n" + "#include <string.h>\n\n" + "int main()\n" + "{\n" + " char *s1 = (char*)malloc(12*sizeof(char));\n" + " char *s2 = (char*)malloc(12*sizeof(char));\n" + " gets(s1);\n" + " int a = atoi(s1);\n" + " sprintf(s2,\"%d\",a);\n" + " if(strcmp(s1,s2)==0)\n" + " printf(\"Yes\");\n" + " else\n" + " printf(\"No\");\n\n" + "}\n\n" + "//bound checking for the LCM\n" + "#include <stdio.h>\n" + "#include <stdlib.h>\n" + "#include <limits.h>\n\n" + "unsigned long long gcd(unsigned long long a, unsigned long long b) {\n" + " unsigned long long temp = 0;\n" + " while (b != 0)\n" + " {\n" + " temp = a % b;\n" + " a = b;\n" + " b = temp;\n" + " }\n" + " return a;\n" + "}\n\n" + "int main(void) {\n" + " unsigned long long a, b;\n" + " scanf(\"%llu %llu\", &a, &b);\n\n" + " unsigned long long UCLN = gcd(a,b);\n" + " if(a==0||b==0)\n" + " printf(\"N/A\");\n" + " else if((a/UCLN) <= (ULLONG_MAX/b))\n" + " printf(\"%llu\",a/UCLN*b);\n" + " else{\n" + " printf(\"N/A\");\n" + " }\n\n" + " return 0;\n" + "}\n\n\n\n\n" + "//dual format telephone number\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex phone10(\"(\\\\+84|0)1[0-9]{9}\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, phone10))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n\n" + "//email address\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "int main(){\n" + " regex pattern(\"([\\\\w!#$%&'*+/=?^_`{|}~-]+\\\\.?[\\\\w!#$%&'*+/=?^_`{|}~-]+)+@(\\\\w+(\\\\-\\\\w+)?(\\\\.\\\\w+))+\");\n" + " int x;\n" + " cin >>x;\n" + " string line_;\n" + " getline(cin,line_);\n" + " while(x--){\n" + " getline(cin,line_);\n" + " if(regex_match(line_,pattern))\n" + " cout << \"Valid!\"<<endl;\n" + " else\n" + " cout <<\"Invalid!\"<<endl;\n" + " }\n" + " return 0;\n" + "}\n\n\n\n" + "//find IP attack\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "int main(){\n" + " regex pattern(\"\\\\d+\\\\ \\\\d+\\\\.\\\\d+(\\\\ ((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\\\\.){3}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])){2}\\\\ [A-Z]+\\\\ \\\\d+ [A-Z]+\\\\ [\\\\w-+/?=&.: ]+\");\n" + " int t;\n" + " string st;\n" + " cin >> t;\n" + " getline(cin, st);\n" + " int i = 1;\n" + " while(t--){\n" + " getline(cin, st);\n" + " cout << i++ << endl;\n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), pattern, 0);\n" + " sregex_token_iterator end;\n" + " for (; pos!=end; ++pos)\n" + " cout << \"Found \" << pos->str() << endl;\n" + " }\n" + " return 0;\n" + "}\n\n\n\n" + "//integer number\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex pattern(\"[\\\\+-]?[1-9][0-9]*\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, pattern))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n\n" + "//list email in raw data\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "int main(){\n" + " regex pattern(\"([\\\\w_-]+(\\\\.?[\\\\w_-]))+@[\\\\w]+([_\\\\w]+)?(\\\\.[\\\\w]+)+\");\n" + " int t;\n" + " string st;\n" + " cin >> t;\n" + " getline(cin, st);\n" + " int i = 1;\n" + " while(t--){\n" + " getline(cin, st);\n" + " cout << i++ << endl;\n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), pattern, 0);\n" + " sregex_token_iterator end;\n" + " for (; pos!=end; ++pos)\n" + " cout << \"Found \" << pos->str()<< endl;\n" + " }\n" + " return 0;\n" + "}\n\n\n\n\n" + "//list IP in log web\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "int main(){\n" + " regex pattern(\"((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\\\\.){3}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\");\n" + " int t;\n" + " string st;\n" + " cin >> t;\n" + " getline(cin, st);\n" + " int i = 1;\n" + " while(t--){\n" + " getline(cin, st);\n" + " cout << i++ << endl;\n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), pattern, 0);\n" + " sregex_token_iterator end;\n" + " for (; pos!=end; ++pos)\n" + " cout << \"Found \" << pos->str()<< endl;\n" + " }\n" + " return 0;\n" + "}\n\n\n\n\n" + "//list link in a tag HTML\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "int main(){\n" + " regex pattern(\"(http|https|ftp)://[\\\\w\\\\.]+([-\\\\w\\\\.]+)?(:\\\\d+)?([/\\\\w]+)?\");\n" + " int t;\n" + " string st;\n" + " cin >> t;\n" + " getline(cin, st);\n" + " int i = 1;\n" + " while(t--){\n" + " getline(cin, st);\n" + " cout << i++ << endl;\n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), pattern, 0);\n" + " sregex_token_iterator end;\n" + " for ( ; pos!=end ; ++pos )\n" + " cout << \"Found: \" << pos->str()<< endl;\n" + " }\n" + " return 0;\n" + "}\n\n\n\n" + "//list phone number\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex pattern(\"((\\\\+84)|0)[1-9][0-9]{8,9}\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin, st);\n" + " for(int i=1;i<=n;i++){\n" + " cout << i << endl;\n" + " getline(cin, st);\n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), pattern, 0);\n" + " sregex_token_iterator end;\n" + " for ( ; pos!=end ; ++pos ) {\n" + " cout << \"Found \" << pos->str() << \" at \" << pos->first-st.begin() << endl;\n" + " }\n" + " } \n" + " return 0;\n" + "}\n\n\n\n" + "//matching specific FileName\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "int main(){\n" + " regex images(\"[a-zA-Z0-9\\\\_\\\\.]+\\\\.?[a-zA-Z0-9\\\\_]+\\\\.(([jJ][pP][gG])|([pP][nN][gG])|([gG][iI][fF]))\");\n" + " regex docs(\"[a-zA-Z0-9\\\\_\\\\.]+\\\\.?[a-zA-Z0-9\\\\_]+\\\\.(([pP][dD][f|])|([dD][oO][cC])|([pP]{2}[tT][xX]))\");\n" + " regex media(\"[a-zA-Z0-9\\\\_\\\\.]+\\\\.?[a-zA-Z0-9\\\\_]+\\\\.(([m|M][p|P][3|4])|([a|A][v|V][i|I]))\");\n" + " int t;\n" + " string st;\n" + " cin >> t;\n" + " getline(cin, st);\n" + " int i = 1;\n" + " while(t--){\n" + " getline(cin, st);\n" + " cout << i++ << endl;\n" + " \n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), images, 0);\n" + " sregex_token_iterator end;\n" + " for ( ; pos!=end ; ++pos )\n" + " cout << pos->str() << \" : \" << \"hinh anh\" << endl;\n" + " \n" + " sregex_token_iterator pos1(st.cbegin(),st.cend(), media, 0);\n" + " sregex_token_iterator end1;\n" + " for ( ; pos1!=end1 ; ++pos1 )\n" + " cout << pos1->str() << \" : \" << \"media\" << endl;\n" + " \n" + " sregex_token_iterator pos2(st.cbegin(),st.cend(), docs, 0);\n" + " sregex_token_iterator end2;\n" + " for ( ; pos2!=end2 ; ++pos2 )\n" + " cout << pos2->str() << \" : \" << \"tai lieu\" << endl;\n" + " }\n" + " return 0;\n" + "}\n\n\n\n\n" + "//modify telephone number\n" + "#include <iostream>\n" + "#include <regex>\n" + "#include <string>\n" + "using namespace std;\n\n" + "string Convert(string str){\n" + " string temp = \"\";\n" + " string sub = str.substr(0,4);\n" + " if(sub.compare(\"0123\") ==0){\n" + " regex at_sign(\"0123\");\n" + " string replace_by(\"083\");\n" + " temp = regex_replace(str, at_sign, replace_by);\n" + " }else if(sub.compare(\"0124\") ==0){\n" + " regex at_sign(\"0124\");\n" + " string replace_by(\"084\");\n" + " temp = regex_replace(str, at_sign, replace_by);\n" + " }else if(sub.compare(\"0125\") ==0){\n" + " regex at_sign(\"0125\");\n" + " string replace_by(\"085\");\n" + " temp = regex_replace(str, at_sign, replace_by);\n" + " }\n" + " else if(sub.compare(\"0127\") ==0){\n" + " regex at_sign(\"0127\");\n" + " string replace_by(\"081\");\n" + " temp = regex_replace(str, at_sign, replace_by);\n" + " }\n" + " else if(sub.compare(\"0129\") ==0){\n" + " regex at_sign(\"0129\");\n" + " string replace_by(\"082\");\n" + " temp = regex_replace(str, at_sign, replace_by);\n" + " }\n" + " return temp;\n" + "}\n" + "int main(){\n" + " regex pattern(\"012[3-9^6]\\\\d{7}\");\n" + " int t;\n" + " string st;\n" + " cin >> t;\n" + " getline(cin, st);\n\n" + " for(int i = 1; i <= t ; i++){\n" + " getline(cin, st);\n" + " cout << i << endl;\n" + " sregex_token_iterator pos(st.cbegin(),st.cend(), pattern, 0);\n" + " sregex_token_iterator end;\n" + " for (; pos!=end; ++pos){\n" + " string str1 = pos->str();\n" + " cout << \"Thay doi: \" << Convert(str1) << endl;\n" + " }\n" + " }\n" + " return 0;\n" + "}\n\n\n\n" + "//numeric string leading without zero\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex pattern(\"[1-9][0-9]*\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, pattern))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n\n" + "//numeric string\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex pattern(\"[0-9]*\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, pattern))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n\n" + "//telephone number international format\n" + "#include<iostream>\n" + "#include<regex>\n" + "#include <string>\n" + "#include <stdexcept>\n" + "using namespace std;\n" + "int main()\n" + "{\n" + " regex phone10(\"\\\\+841(\\\\.[0-9]{3}){3}\");\n" + " string st;\n" + " int n;\n" + " cin >> n;\n" + " getline(cin,st);\n" + " while(n--){\n" + " getline(cin, st);\n" + " if(regex_match(st, phone10))\n" + " cout << \"Valid!\" << endl;\n" + " else\n" + " cout << \"Invalid!\" << endl;\n" + " }\n" + " \n" + " return 0;\n" + "}\n\n\n\n"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html