#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char *str_replace(char *source, char *sub, char *rep)
{
                char *result;
                char *pc1, *pc2, *pc3;
                int isource, isub, irep;
                isub = strlen(sub);
                irep = strlen(rep);
                isource = strlen(source);
                if(NULL == *sub)
                                return strdup(source);

                result = (char *)malloc(((irep > isub) ? (float)strlen(source)/isub*irep+1:isource)*sizeof(char));
                pc1 = result;
                while(*source != NULL)
                {
                                pc2 = source;
                                pc3 = sub;

                                while(*pc2 == *pc3 && *pc3 != NULL && *pc2 != NULL)
                                                pc2++, pc3++;

                                if(NULL == *pc3)
                                {
                                                pc3 = rep;
                                                while(*pc3 != NULL)
                                                                *pc1++ = *pc3++;
                                                pc2--;
                                                source = pc2;
                                }
                                else
                                                *pc1++ = *source;
                                source++;
                }
                *pc1 = NULL;
                return result;
}

main()
{
                FILE *fp;
                char buf[128] = "";
                char s2[]="<";
                char s3[]="&lt";
                char s4[]=">";
                char s5[]="&gt";

                printf("Content-type:text/html\n\n");

                printf("<pre>\n");
                if(NULL !=(fp=popen("/sbin/ifconfig -a", "r")))
                {
                                while(!feof(fp) && fgets(buf,sizeof(buf),fp))
                                {
                                                printf("%s",str_replace(str_replace(buf,s2,s3),s4,s5));
                                }
                }
                printf("</pre>");

}