Notes

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#define buffer_size 4096


int main(int argc, char* argv[]) {

int fd; //file descriptor
char buffer[buffer_size]; //buffer storing characters
char lines[buffer_size];
int num_lines=0;
int current_line=0; //num telling current line which is being read
int read_lines=0; //lines that have to be read as said by user
ssize_t input;

//assertion for entering text file name
if(argc != 3){
printf ("File name is compulsory to enter");
return 1;
}
read_lines=atoi(argv[1]);


//opening file using linux sytem call
fd = open (argv [2], O_RDONLY);
if (fd == -1) {
perror ("Error occured!");
return 2;
}


//reading file
while((input = read (fd, &buffer, 1)) > 0){
//strcmp compares.It returns zero when strings passed in its arguments are same
if (strcmp(buffer,".")==0) {
num_lines++;
}
}
//closing of file
close (fd);


fd = open (argv [2], O_RDONLY);
while((input = read (fd, &buffer, 1)) > 0){
strcat(lines,buffer);
if (strcmp(buffer,".")==0) {
current_line++;
if(current_line>(num_lines+read_lines)){
printf("%s",lines); //printing of lines

}
memset(lines, 0, buffer_size);

}}
return (EXIT_SUCCESS);
}