Programming

 /*my tiny tail, it prints the last 5 line of a file
*/
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#define MAXSIZE 5000
void flush(char* buff,int n);
int main(int argc,char*argv[]){
    int i,n,fd,count;
    char buff[MAXSIZE];
    if (argc<2){printf("no file name inserted\n"),exit(1);}
    else if(argc>2) printf("too many parameters\n"),exit(1);
    else{    
        if((fd=open(argv[1],O_RDONLY))<0) {perror("open error"),exit(1);}
        /*file opened in readonly mode*/
        lseek(fd,-1,SEEK_END);/*the offset points the char before the end of file*/
        count=0;
        i=MAXSIZE;
        flush(buff,MAXSIZE);/*clean the buffer*/
        while(count!=5){
            if((read(fd,&buff[i],sizeof(char)))<0) perror("read error"),exit(1);
            if(buff[i]=='\n') ++count;/*count increments when the program meet a new line */
            --i;
            lseek(fd,-2,SEEK_CUR);/*read puts the offset one char forward */
            }
        for(n=i;n<MAXSIZE-1;++n)
            printf("%c",buff[n]);
        printf("\n");
        close(fd);
        }
    return 0;    
}
void flush(char* buff,int n){
    int i;
    for(i=0;i<n;++i) buff[i]=0;
}