说明:只写了C段D段例:172.16.0.0 172.16.255.255

编译:gcc ip.c -o ip

#include <stdio.h>
int main()
{
int i,ii,iii,i1,i2,ch;
int n=0;
char w3[36];
FILE *fp;
FILE *fp1;
//检测行数
fp=fopen("ip.txt","r");
 while((ch = fgetc(fp)) != EOF) 
{if(ch == '\n'){n++;}}  
fclose(fp);
//逐行读取
fp=fopen("ip.txt","r+");
for(i=1;i<=n;i++){
fgets(w3,100,fp);
int da0,da1,da2,da3,da4,da5,da6,da7;
sscanf(w3,"%d.%d.%d.%d %d.%d.%d.%d",&da0,&da1,&da2,&da3,&da4,&da5,&da6,&da7);
for(i2 = da0; i2 <= da4; i2++){
for(i1 = da1; i1 <= da5; i1++){
for(ii = da2; ii <= da6; ii++){
        if (ii==da2){
            for(iii = da3; iii <= 255; iii++)
            {
                printf("%d.%d.%d.%d\n",i2,i1,ii,iii);          
            }
            ii++;
        }
        if(ii<da6){
            //ii++; 
        for(iii = 0; iii <= 255; iii++)
            {
                printf("%d.%d.%d.%d\n",i2,i1,ii,iii);           
            } 
        }
        else {
            for(iii = 0; iii <= da7; iii++)
            {
                fp1=fopen("ips.txt","a+");
                fprintf(fp1,"%d.%d.%d.%d\n",i2,i1,ii,iii);
                fclose(fp1);     
            }   
        }
}}}
//for结束
}
 fclose(fp);  
    return 0;
}