c语言 正则表达式 IP地址

#include <stdio.h>
#include <string.h>
#include <regex.h>

#define SUBSLEN 10              /* 匹配子串的数量 */
#define EBUFLEN 128             /* 错误消息buffer长度 */
#define BUFLEN 1024             /* 匹配到的字符串buffer长度 */

int main()
{
size_t          len;
regex_t         re;             /* 存储编译好的正则表达式，正则表达式在使用之前要经过编译 */
regmatch_t      subs [SUBSLEN];     /* 存储匹配到的字符串位置 */
char            matched   [BUFLEN];     /* 存储匹配到的字符串 */
char            errbuf    [EBUFLEN];    /* 存储错误消息 */
int             err, i;

char            src       [] = "sdafsdfsdf52.23.11.43sdafsdfsdfasdfa";    /* 源字符串 */
char            pattern   [] = "([0-9]{1,3}[.]){3}[0-9]{1,3}";    /* pattern字符串 */

printf("String : %s\n", src);
printf("Pattern: \"%s\"\n", pattern);

/* 编译正则表达式 */
err = regcomp(&re, pattern, REG_EXTENDED);

if (err) {
len = regerror(err, &re, errbuf, sizeof(errbuf));
printf("error: regcomp: %s\n", errbuf);
return 1;
}
printf("Total has subexpression: %d\n", re.re_nsub);
/* 执行模式匹配 */
err = regexec(&re, src, (size_t) SUBSLEN, subs, 0);

if (err == REG_NOMATCH) { /* 没有匹配成功 */
printf("Sorry, no match ...\n");
regfree(&re);
return 0;
} else if (err) {  /* 其它错误 */
len = regerror(err, &re, errbuf, sizeof(errbuf));
printf("error: regexec: %s\n", errbuf);
return 1;
}

/* 如果不是REG_NOMATCH并且没有其它错误，则模式匹配上 */
printf("\nOK, has matched ...\n\n");
for (i = 0; i <= re.re_nsub; i++) {
len = subs[i].rm_eo - subs[i].rm_so;
if (i == 0) {
printf ("begin: %d, len = %d  ", subs[i].rm_so, len); /* 注释1 */
} else {
printf("subexpression %d begin: %d, len = %d  ", i, subs[i].rm_so, len); 
}
memcpy (matched, src + subs[i].rm_so, len);
matched[len] = '\0';
printf("match: %s\n", matched);
}

regfree(&re);   /* 用完了别忘了释放 */
return (0);
}