/* * regex.c - 用正則表達式驗證電子郵件地址 * *  POSIX正則表達式 * * * 編譯命令： *  gcc regex.c -o regex -Wall * * *  Copyright 葉劍飛 2012 * */#include <stdio.h>#include <stdlib.h>#include <string.h>#include <regex.h> /* regular expression 正則表達式 */#define MAX_LENGTH 1000int main (void){ size_t char_num; char email_address[MAX_LENGTH]; char user_name[MAX_LENGTH]; char domain_name[MAX_LENGTH]; regmatch_t pmatch[4]; regex_t match_regex; regcomp( &match_regex,  "([0-9A-Za-z//-_//.]+)@([0-9a-z]+//.[a-z]{2,3}(//.[a-z]{2})?)",  REG_EXTENDED ); while ( scanf( "%s", email_address ) != EOF ) { if ( regexec( &match_regex, email_address, 4, pmatch, 0 ) == 0 ) {  char_num = pmatch[1].rm_eo - pmatch[1].rm_so;  strncpy( user_name, &(email_address[pmatch[1].rm_so]), char_num );  user_name[char_num] = '/0';  char_num = pmatch[2].rm_eo - pmatch[2].rm_so;  strncpy( domain_name, &(email_address[pmatch[2].rm_so]), char_num );  domain_name[char_num] = '/0';  puts( "您輸入的電子郵件地址合法" );  printf ( "用戶名：%s/n", user_name );  printf ( "域名：%s/n/n", domain_name ); } else  puts( "您輸入的電子郵件地址不合法/n/n" ); } regfree( &match_regex ); return EXIT_SUCCESS;}