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#include <stdio.h>#include <string.h>#include <fcntl.h>#include <sys/stat.h>#include "hacking.h"#define FILENAME "/var/notes"int print_notes(int, int, char *);   // note printing functionint find_user_note(int, int);        // seek in file for a note for userint search_note(char *, char *);     // search for keyword functionvoid fatal(char *);                  // fatal error handlerint main(int argc, char *argv[]) {	int userid, printing=1, fd; // file descriptor	char searchstring[100];	if(argc > 1)                        // If there is an arg		strcpy(searchstring, argv[1]);   //   that is the search string	else                                // otherwise		searchstring[0] = 0;             //   search string is empty	userid = getuid();	fd = open(FILENAME, O_RDONLY);   // open the file for read-only access	if(fd == -1)		fatal("in main() while opening file for reading");	while(printing)		printing = print_notes(fd, userid, searchstring);	printf("-------[ end of note data ]-------\n");	close(fd);}// A function to print the notes for a given uid that match// an optional search string// returns 0 at end of file, 1 if there are still more notesint print_notes(int fd, int uid, char *searchstring) {	int note_length;	char byte=0, note_buffer[100];		note_length = find_user_note(fd, uid);	if(note_length == -1)  // if end of file reached		return 0;           //   return 0	read(fd, note_buffer, note_length); // read note data	note_buffer[note_length] = 0;       // terminate the string		if(search_note(note_buffer, searchstring)) // if searchstring found		printf(note_buffer);                    //   print the note	return 1;}// A function to find the next note for a given userID// returns -1 if the end of the file is reached// otherwise it returns the length of the found noteint find_user_note(int fd, int user_uid) {	int note_uid=-1;	unsigned char byte;	int length;	while(note_uid != user_uid) {  // loop until a note for user_uid is found		if(read(fd, &note_uid, 4) != 4) // read the uid data			return -1; // if 4 bytes aren't read, return end of file code		if(read(fd, &byte, 1) != 1) // read the newline separator         return -1;		byte = length = 0;		while(byte != '\n') {  // figure out how many bytes to the end of line			if(read(fd, &byte, 1) != 1) // read a single byte				return -1;     // if byte isn't read, return end of file code			length++;  		}	}	lseek(fd, length * -1, SEEK_CUR); // rewind file reading by length bytes	printf("[DEBUG] found a %d byte note for user id %d\n", length, note_uid);	return length;}// A function to search a note for a given keyword// returns 1 if a match is found, 0 if there is no matchint search_note(char *note, char *keyword) {	int i, keyword_length, match=0;	keyword_length = strlen(keyword);	if(keyword_length == 0)  // if there is no search string		return 1;              // always "match"		for(i=0; i < strlen(note); i++) { // iterate over bytes in note		if(note[i] == keyword[match])  // if byte matches keyword			match++;   // get ready to check the next byte		else {        //   otherwise			if(note[i] == keyword[0]) // if that byte matches first keyword byte				match = 1;  // start the match count at 1			else				match = 0;  // otherwise it is zero		}		if(match == keyword_length) // if there is a full match			return 1;   // return matched	}	return 0;  // return not matched}