/*********************************************************************************
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* Copyright: (C) 2025 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: popen.c
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* Description: This file is popen() example program.
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*
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* Version: 1.0.0(10/28/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "10/28/2025 11:02:28 AM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <ctype.h>
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int get_ipaddr(char *interface, char *ipaddr, int ipaddr_size);
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int main(int argc, char **argv)
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{
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char ipaddr[16];
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char *interface="enp2s0";
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memset(ipaddr, 0, sizeof(ipaddr));
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if( get_ipaddr(interface, ipaddr, sizeof(ipaddr)) < 0 )
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{
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printf("ERROR: get IP address failure\n");
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return -1;
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}
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printf("get network interface %s IP address [%s]\n", interface, ipaddr);
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return 0;
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}
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int get_ipaddr(char *interface, char *ipaddr, int ipaddr_size)
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{
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char buf[1024];
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char *ptr;
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char *ip_start;
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char *ip_end;
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FILE *fp;
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int len;
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int rv;
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if( !interface || !ipaddr || ipaddr_size<16 )
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{
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printf("Invalid input arguments\n");
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return -1;
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}
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memset(buf, 0, sizeof(buf));
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snprintf(buf, sizeof(buf), "ifconfig %s", interface);
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if( NULL == (fp=popen(buf, "r")) )
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{
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printf("popen() to excute command \"%s\" failure: %s\n", buf, strerror(errno));
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return -2;
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}
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rv = -3; /* Set default return value to -3 means parser failure */
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while( fgets(buf, sizeof(buf), fp) )
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{
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if( strstr(buf, "netmask") )
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{
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ptr=strstr(buf, "inet");
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if( !ptr )
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{
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break;
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}
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ptr += strlen("inet");
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while( isblank(*ptr) )
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ptr++;
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ip_start = ptr;
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while( !isblank(*ptr) )
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ptr++;
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ip_end = ptr;
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memset(ipaddr, 0, sizeof(ipaddr));
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len = ip_end-ip_start;
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len = len>ipaddr_size ? ipaddr_size : len;
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memcpy(ipaddr, ip_start, len);
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rv = 0; /* Parser IP address OK and set rv to 0 */
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break;
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}
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}
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return rv;
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}
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