#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include "hacking.h"
#define FILENAME "/var/note"
int print_notes(int, int, char *); // note printing function
int find_user_note(int, int); // seek in file for a note for user
int search_note(char *, char *); // search for keyword function
void fatal(char *); // fatal error handler
int 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 notes
int 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
int readResult = read(fd, note_buffer, note_length); // read note data
if (readResult != note_length)
fatal("in print_notes() while reading bytes");
note_buffer[note_length] = 0; // terminate the string
if(search_note(note_buffer, searchstring)) // if searchstring found
printf("%s", 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 note
int find_user_note(int fd, int user_uid) {
int note_uid=-1;
unsigned char byte;
int length;
long int initialPosition = 0;
while(note_uid != user_uid) { // loop until a note for user_uid is found
if(read(fd, ¬e_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;
initialPosition = lseek(fd, 0, SEEK_CUR);
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, initialPosition, SEEK_SET); // rewind file
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 match
int 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
}
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