IP地址与点分十进制串的相互转换

概述

最近在学习Unix/Linux上的网络编程,遇到了IP地址与点分十进制串之间相互转换的问题,
所以写了两个程序用以实现它们之间的相互转换,以备不时之需.

十六进制参数转换为点分十进制串

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// a file named hexTodd.c 

#include    <stdio.h>
#include    <stdlib.h>
#include    <ctype.h>
#include    <arpa/inet.h>

#define MAXBUF   8192  /* Max I/O buffer size */

int main(int argc, char *argv[])
{
    struct in_addr inaddr;
    uint32_t addr;
    long check;
    char buf[MAXBUF];
    int i = 0, m = 2;


    if(argc != 2){
        fprintf(stderr,"Usage: %s <hex number>   for example: %s 0xfa256fd\n",argv[0], argv[0]);
        exit(1);
    }
    if(argv[1][0] != '0' && (argv[1][1] != 'x' || argv[1][1] != 'X')){
        fprintf(stderr,"Usage: %s <hex number>   for example: %s 0xfa256fd\n",argv[0], argv[0]);
        exit(1);
    }
    sscanf(argv[1],"%lx",&check);
    if(check > 0xffffffff ){
        fprintf(stderr,"The input max hex number should be 0xffffffff\n");
        fprintf(stderr,"Usage: %s <hex number>   for example: %s 0xfa256fd\n",argv[0], argv[0]);
        exit(1);
    }
    while(argv[1][i] && argv[1][m]){
        if(argv[1][0] == '0' && (argv[1][1] == 'x' || argv[1][1] == 'X' )){
            if(isxdigit(argv[1][m])){
                ++m;
                ++i;
            }else{
                printf("In (0x)%s, %c is not a hex number!\n",argv[1],argv[1][m]);
                fprintf(stderr,"Usage: %s <hex number>   for example: %s 0xfa256fd\n",argv[0], argv[0]);
                exit(1);
            }
        }else{
            if(isxdigit(argv[1][i])){
               ++i;
            }else{
                printf("In (0x)%s, %c is not a hex number!\n",argv[1],argv[1][i]);
                fprintf(stderr,"Usage: %s <hex number>   for example: %s 0xfa256fd\n",argv[0], argv[0]);
                exit(1);
            }
        }
    }

    sscanf(argv[1],"%x",&addr);
    inaddr.s_addr = htonl(addr);

    if(!inet_ntop(AF_INET, &inaddr, buf, MAXBUF)){
        printf("inet_ntop\n");
    }
    else{
        printf("%s\n",buf);
    }

    return 0;
}

用下面的命令编译并运行:

cc -g -o hexTodd hexTodd.c
./hexTodd

使用样例:

haha@hello:~/.../test-code$ ./hexTodd
Usage: ./hexTodd <(0x)hex number>
haha@hello:~/.../test-code$ ./hexTodd 8002c2f2
128.2.194.242
haha@hello:~/.../test-code$ ./hexTodd 0x8002c2f2
128.2.194.242
haha@hello:~/.../test-code$ ./hexTodd 0X8002c2f2
128.2.194.242
haha@hello:~/.../test-code$ ./hexTodd 8002c2f2x
In (0x)8002c2f2x, x is not a hex number!
Usage: ./hexTodd <(0x)hex number>
haha@hello:~/.../test-code$ ./hexTodd 8ac7dlpds
In (0x)8ac7dlpds, l is not a hex number!
Usage: ./hexTodd <(0x)hex number>
haha@hello:~/.../test-code$

点分十进制参数转换为十六进制数

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// a file named ddTohex.c

#include <stdio.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
    struct in_addr inaddr;  /* Address in network byte order */
    int rc;

    if (argc != 2) {
	fprintf(stderr, "usage: %s <dotted-decimal>\n", argv[0]);
    return 0;
    }

    rc = inet_pton(AF_INET, argv[1], &inaddr);
    if (rc == 0)
	printf("inet_pton error: invalid dotted-decimal address");
    else if (rc < 0)
        printf("inet_pton error");

    printf("0x%x\n", ntohl(inaddr.s_addr));
    return 0;
}

用下面的命令编译并运行:

cc -g -o ddTohex ddTohex.c
./ddTohex

使用样例:

haha@hello:~/.../test-code$ ./ddTohex
usage: ./ddTohex <dotted-decimal>
haha@hello:~/.../test-code$ ./ddTohex 128.2.194.242
0x8002c2f2
haha@hello:~/.../test-code$ ./ddTohex 1452.2253.2555.123
inet_pton error: invalid dotted-decimal address0xafffff
haha@hello:~/.../test-code$ ./ddTohex 126.125.252.8956
inet_pton error: invalid dotted-decimal address0xafffff
haha@hello:~/.../test-code$