确定字符串是否是C中的有效IPv4地址
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确定字符串是否包含IPv4地址的好方法是什么？我应该使用isdigit()吗？
答案
我问a similar question for C++。您应该能够使用我当时提出的稍微修改过的（对于C）版本。
bool isValidIpAddress(char *ipAddress)
{
struct sockaddr_in sa;
int result = inet_pton(AF_INET, ipAddress, &(sa.sin_addr));
return result != 0;
}
你需要使用#include <arpa/inet.h>来使用inet_pton()函数。
根据对问题的评论进行更新：如果您想知道C风格的字符串是否包含IP地址，那么您应该结合到目前为止给出的两个答案。使用正则表达式查找与IP地址大致匹配的模式，然后使用上面的函数检查匹配项以查看它是否真实。
另一答案
这是我一直在努力的功能的开始，虽然不完整，它可能会引发想法或评论。功能背后的思想是;
- 检查传递的char指针或字符串是否是一个没有端口的IPv4地址，使用其最小/最大大小，字符串中有多少个点，以及冒号：字符是否存在。
- 如果字符串不是带有或没有端口的IPv4，那么检查该字符串是否为IPv6，如果不是IPv6，则无法识别IP格式，因为它尚未实现。
我认为这取决于你想要深入研究这个问题的深度，你想要了解可能会出现什么样的问题。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <arpa/inet.h>
int isIP(char *ip)
{
char *data_ptr = ip; // Create a pointer to passed data
int orig_str_size = 0; // Create an int to hold passed data size
int str_index = 0; // Create an int to iterate individual ip characters
int dot_count = 0; // Create an int to check for the number of dots
// Count the number of characters in data_ptr
while (*data_ptr++ != ' '){ orig_str_size++; }
if(orig_str_size <= 0) // If nothing
{
printf("Get a grip, ip is empty
");
exit(0);
}
else // If within IPv4 size range
if(orig_str_size >= 7 && orig_str_size <= INET_ADDRSTRLEN)
{
char *data1_ptr = ip; // Create a pointer to passed data
printf("Within IPv4 range, %i characters in length
", orig_str_size);
// Count the number of dots in the string, 3 for IPv4
for(str_index; str_index < orig_str_size; str_index++)
{
if(data1_ptr[str_index] == '.'){ dot_count++; }
}
// If theres 3 dots, while ignoring dots, check each char is a digit
if(dot_count == 3)
{
printf("There's three dots in the string
");
data1_ptr = ip;
str_index = 0;
// Iterate the string char by char
for(str_index; str_index < orig_str_size; str_index++)
{
// Ignoring dots
if(data1_ptr[str_index] != '.')
{
// If isdigit() is happy its a digit and isalpha() happy not alphabetic
if(isdigit(data1_ptr[str_index]) && !isalpha(data1_ptr[str_index]))
{
printf("Digit found and is not alphabetic
");
continue;
}
else
if(!isdigit(data1_ptr[str_index]) && isalpha(data1_ptr[str_index]))
{
printf("Not a recognised IPv4 address, character detected in string
");
exit(0);
}
}
}
return 0;
}
}
else // If IPv6
if(orig_str_size > 0 && orig_str_size > INET_ADDRSTRLEN && orig_str_size <= INET6_ADDRSTRLEN)
{
printf("Within IPv6 range %i
", orig_str_size);
return 0;
}
else
{
printf("Unknown target format, the format you provided as a target is not implemented
");
exit(0);
}
}
TCP / IP网络互联
RFC791 - 互联网协议 - https://tools.ietf.org/html/rfc791
CISCO网络互联手册http://docwiki.cisco.com/wiki/Internetworking_Technology_Handbook
开放系统互连参考模型http://docwiki.cisco.com/wiki/Internetworking_Basics#Open_Systems_Interconnection_Reference_Model
CISCO故障排除TCP / IP网络https://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1907.pdf
What is the largest TCP/IP network port number allowable for IPv4?
另一答案
// you can even use the v value array to return the unsigned int
// version of the IP if desired in an unsigned int reference.
bool isvalidip(const char * s)
{
char t[8];
int p = 0;
int v[8];
int numnum = 0;
for (int i = 0; i < (int) strlen(s); i++) {
char c = s[i];
int cgood = 0;
if (c >= '0' && c <= '9' && p < 4) {
t[p++] = c;
t[p] = 0;
cgood++;
continue;
}
if (p == 4) return false;
if (c == '.') {
if (!p) return false;
v[numnum++] = atoi(t);
p = 0;
cgood++;
continue;
}
if (!cgood) return false; // not a valid character
if (numnum > 4) return false; // we have a lot of dots....
}
v[numnum++] = atoi(t); // we did not have a dot, we had a NULL.....
if (numnum != 4) return false; // we must have had 4 valid numbers....
for (int i = 0; i < 4; i++)
{
if (v[i] < 0 || v[i] > 255) return false; // octet values out-of-range
}
return true; //we good..
}
另一答案
我修改了其中一个答案，使其更加完整并附上所有代码（包括测试）
#include <stdio.h>
#include <assert.h>
#include <string.h>
int validateIP4Dotted(char *str, unsigned int pIPAddress[])
{
int segs = 0; /* Segment count. */
int chcnt = 0; /* Character count within segment. */
int accum = 0; /* Accumulator for segment. */
/* Catch NULL pointer. */
if (str == NULL)
return 0;
/* Process every character in string. */
while (*str != ' ')
{
/* Segment changeover. */
if (*str == '.')
{
pIPAddress[segs] = accum;
/* Must have some digits in segment. */
if (chcnt == 0 || chcnt > 3)
return 0;
/* Limit number of segments. */
if (++segs == 4)
return 0;
/* Reset segment values and restart loop. */
chcnt = accum = 0;
str++;
continue;
}
/* Check numeric. */
if ((*str < '0') || (*str > '9'))
return 0;
/* Accumulate and check segment. */
if ((accum = accum * 10 + *str - '0') > 255)
return 0;
/* Advance other segment specific stuff and continue loop. */
chcnt++;
str++;
}
/* Check enough segments and enough characters in last segment. */
pIPAddress[segs] = accum;
if (segs != 3)
return 0;
if (chcnt == 0 || chcnt > 3)
return 0;
if (pIPAddress[0] >=224)
return 0;
/* Address okay. */
return 1;
}
int main()
{
unsigned int IpAddress[4];
char str_ip[128];
strcpy(str_ip, "192.168.1.10");
assert(validateIP4Dotted(str_ip, IpAddress));
assert(
IpAddress[0] == 192 && IpAddress[1] == 168 && IpAddress[2] == 1
&& IpAddress[3] == 10);
strcpy(str_ip, "0.0.0.0");
assert(validateIP4Dotted(str_ip, IpAddress));
assert(
IpAddress[0] == 0 && IpAddress[1] == 0 && IpAddre以上是关于确定字符串是否是C中的有效IPv4地址的主要内容，如果未能解决你的问题，请参考以下文章