Determines whether the string is an IP address.

Determines whether the string is an IP address.

Method 1:

# Include <sys/types. h>

# Include <sys/socket. h>

# Include <netinet/in. h>

# Include <ARPA/inet. h>

# Include <errno. h>

Int if_a_string_is_a_valid_1_4_address (const char * Str)

{

Struct in_addr ADDR;

Int ret;

Ret = inet_ton (af_inet, STR, & ADDR );

If (Ret> 0)

Fprintf (stderr, "\" % s \ "is a valid IPv4 address \ n", STR );

Else if (Ret <0)

Fprintf (stderr, "eafnosupport: % s \ n", strerror (errno ));

Else

Fprintf (stderr, "\" % s \ "is not a valid IPv4 address \ n", STR );

Return ret;

}

Int inet_ton (INT family, const char * strptr, void * addrptr );

Return Value: 1-success; 0-the input is not a valid expression format;-1-error.

Method 2:

# Include <stdio. h>

# Include <string. h>

Int A, B, C, D;

Char T;

Char s [100];

Void main (){

Strcpy (S, "123.1.2.3.1111 ");

If (4 = sscanf (S, "% d. % d. % d. % d % C ", & A, & B, & C, & D, & T )){

If (0 <= A & A <= 255

& 0 <= B & B <= 255

& Amp; 0 & amp; = C & amp; C <= 255

& 0 <= D & D <= 255 ){

Printf ("[% s] is valid IPv4 \ n", S );

} Else {

Printf ("[% s] is invalid IPv4 \ n", S );

}

} Else {

Printf ("[% s] is invalid IPv4 \ n", S );

}

}

Original

Http://bbs.chinaunix.net/thread-928835-1-1.html

Http://www.cnblogs.com/riky/archive/2006/11/24/570713.aspx

Http://bbs.csdn.net/topics/330230349