c语言正则表达式编程 检测ip字符串合法性

写个程序，需要处理ip字符串，在做合法性校验的时候感觉太麻烦，于是想到了正则。看了一下手册，试用一下。

1 源码   检测ipv4字符串的合法性

#include <sys/types.h>
#include <regex.h>

#include <stdio.h>
#include <stdlib.h>

#define IP_PATTERN "^([0-9]|[1-9][0-9]|1[0-9]{1,2}|2[0-4][0-9]|25[0-5]).([0-9]|[1-9][0-9]|1[0-9]{1,2}|2[0-4][0-9]|25[0-5]).([0-9]|[1-9][0-9]|1[0-9]{1,2}|2[0-4][0-9]|25[0-5]).([0-9]|[1-9][0-9]|1[0-9]{1,2}|2[0-4][0-9]|25[0-5])$"


static void regex_emsg(int errorcode, regex_t *preg);

int main(int argc, char *argv[])
{
    regex_t reg;
    regmatch_t match[5];
    int retval;

    if (argc != 2) {
        fprintf(stderr, "usage: %s \n"
                "example: %s 1.2.3.4\n",
                argv[0], argv[0]);
        exit(EXIT_FAILURE);
    }

    retval = regcomp(&reg, IP_PATTERN, REG_EXTENDED | REG_NEWLINE);
    if (retval != 0)
        regex_emsg(retval, &reg);

    retval = regexec(&reg, argv[1], sizeof match / sizeof match[0], match, 0);
    printf("%s is %s\n", argv[1], retval == 0 ? "legal" : "illegal");
    regfree(&reg);

    /*
     * 如果是正确的ip， 输出详细的匹配过程
     */
    if (retval == 0) {
        int i;
        for (i = 1; i < sizeof match / sizeof match[0]; i++) {
            printf("ip part[%d]: %.*s\n", i, match[i].rm_eo - match[i].rm_so,
                    argv[1] + match[i].rm_so);
        }
    }

    exit(EXIT_SUCCESS);

}


/*
 * 输出regexXXX调用出错消息
 */
static void regex_emsg(int errorcode, regex_t *preg)
{
    char msg[512] = {'\0'};

    regerror(errorcode, preg, msg, sizeof msg - 1);
    fputs(msg, stderr);
    fputc('\n', stderr);
    return;
}

    /* filename: regex_checkip.c */

1. 将上面代码编译gcc -Wall regex_checkip.c -o checkip
2. 运行下面的测试基本test.sh ./checkip

2 测试脚本

#!/bin/sh
# filename: test.sh



$1 0.0.0.0
echo ""

$1 1.1.1.1
echo ""
$1 255.255.255.255
echo ""
$1 a1.1.1.1
echo ""
$1 1.1.1.1b
echo ""
$1 256.255.255.255
echo ""
$1 1.23.234.0
echo ""
$1 a.b.sd.d
echo ""
$1 192.168.54.48
echo ""

3 测试结果

0.0.0.0 is legal
ip part[1]: 0
ip part[2]: 0
ip part[3]: 0
ip part[4]: 0

1.1.1.1 is legal
ip part[1]: 1
ip part[2]: 1
ip part[3]: 1
ip part[4]: 1

255.255.255.255 is legal
ip part[1]: 255
ip part[2]: 255
ip part[3]: 255
ip part[4]: 255

a1.1.1.1 is illegal

1.1.1.1b is illegal

256.255.255.255 is illegal

1.23.234.0 is legal
ip part[1]: 1
ip part[2]: 23
ip part[3]: 234
ip part[4]: 0

a.b.sd.d is illegal

192.168.54.48 is legal
ip part[1]: 192
ip part[2]: 168
ip part[3]: 54
ip part[4]: 48

感觉用着还可以。:-)