Решения
Задача 1 - Таблица поиска строк в текстовом файле
lookup1.c
  1 #include <sys/types.h>
  2 #include <fcntl.h>
  3 #include <unistd.h>
  4 #include <stdlib.h>
  5 #include <stdio.h>
  6 #include <string.h>
  7
  8 main(int argc, char *argv[])
  9 {
 10     long displ[500];
 11     int fd, i = 1, j = 0, line_no, line_ln[500];
 12     char c, buf[257];
 13     static char err_msg[32] = "Input file - ";
 14
 15     if(( fd =  open(argv[1], O_RDONLY)) == -1) {
 16         perror(strcat(err_msg, argv[1]));
 17         exit(1);
 18         }
 19
 20     displ[1] = 0L;
 21     while(read(fd, &c, 1))
 22         if( c == '\n' ) {
 23             j++;
 24             line_ln[i++] = j;
 25             displ[i] = lseek(fd, 0L, 1);
 26             j = 0;
 27             }
 28         else
 29             j++;
 30
 31     while( printf("Line number : ") && scanf("%d", &line_no)) {
 32         if(line_no <= 0)
 33             exit(0);
 34         lseek(fd, displ[line_no], 0);
 35         if(read(fd, buf, line_ln[line_no]))
 36             write(1, buf, line_ln[line_no]);
 37         else
 38             fprintf(stderr, "Bad Line Number\n");
 39         }
 40 }
Задача 2 - Таблица поиска строк в текстовом файле
lookup2.c

  1 #include <stdio.h>
  2 #include <unistd.h>
  3 #include <stdlib.h>
  4 #include <fcntl.h>
  5 #include <unistd.h>
  6 #include <string.h>
  7
  8 #define BUFSIZE 257
  9
 10 main(int argc, char *argv[])
 11 {
 12     long displ[500];
 13     int fd1, fd2, i = 1, j = 0, line_no, line_ln[500];
 14     char c, buf[BUFSIZE];
 15     static char err_msg[32] = "Input file - ";
 16
 17     if ((fd1 = open("/dev/tty", O_RDONLY | O_NDELAY)) == -1) {
 18         perror("/dev/tty");
 19         exit(1);
 20     }
 21
 22     if ((fd2 = open(argv[1], O_RDONLY)) == -1) {
 23         perror(strcat(err_msg, argv[1]));
 24         exit(1);
 25         }
 26
 27     displ[1] = 0L;
 28     while(read(fd2, &c, 1))
 29         if( c == '\n' ) {
 30             j++;
 31             line_ln[i++] = j;
 32             displ[i] = lseek(fd2, 0L, 1);
 33             j = 0;
 34             }
 35         else
 36             j++;
 37
 38     for (;;) {
 39         printf("you have 5 seconds to enter a line number\n");
 40         sleep(5);
 41         if ((i = read(fd1, buf, BUFSIZE)) == 0) {
 42             lseek(fd2, SEEK_SET, 0);
 43             while((i = read(fd2, buf, BUFSIZE)) > 0)
 44                 write(1, buf, i);
 45             exit(0);
 46         }
 47         else {
 48             buf[i] = '\0';
 49             line_no = atoi(buf);
 50             if(line_no <= 0)
 51                 exit(0);
 52             lseek(fd2, displ[line_no], 0);
 53             if(read(fd2, buf, line_ln[line_no]))
 54                 write(1, buf, line_ln[line_no]);
 55             else
 56                 fprintf(stderr, "Bad Line Number\n");
 57         }
 58     }
 59 }
Задача 3 - Таблица поиска строк в текстовом файле
lookup3.c

  1 #include <sys/types.h>
  2 #include <stdio.h>
  3 #include <fcntl.h>
  4 #include <unistd.h>
  5 #include <stdlib.h>
  6 #include <string.h>
  7 #include <sys/mman.h>
  8
  9 main(int argc, char *argv[])
 10 {
 11     static char *displ[501];
 12     char *p, buf[10];
 13     int fd1, fd2, count, i = 1, j = 1, line_no, line_ln[500];
 14     static char err_msg[32] = "Input file - ";
 15     off_t size;
 16
 17     if ((fd1 = open("/dev/tty", O_RDONLY | O_NDELAY)) == -1) {
 18         perror("/dev/tty");
 19         exit(1);
 20     }
 21
 22     if ((fd2 = open(argv[1], O_RDONLY)) == -1) {
 23         perror(strcat(err_msg, argv[1]));
 24         exit(1);
 25         }
 26
 27     size = lseek(fd2, 0, SEEK_END);
 28     p = mmap(0, size, PROT_READ, MAP_SHARED, fd2, 0);
 29
 30     displ[1] = p;
 31     for(count = 0; count < size; count++)
 32         if( *(p+count) == '\n' ) {
 33             line_ln[i++] = j;
 34             displ[i] = count+p+1;
 35             j = 1;
 36             }
 37         else
 38             j++;
 39
 40     displ[i] = 0;
 41     for (;;) {
 42         printf("you have 5 seconds to enter a line number\n");
 43         sleep(5);
 44         if ((i = read(fd1, buf, 10)) == 0) {
 45             write(1, p, size);
 46             exit(0);
 47         }
 48         else {
 49             buf[i] = '\0';
 50             line_no = atoi(buf);
 51             if(line_no <= 0)
 52                 exit(0);
 53             if(displ[line_no] != 0)
 54                 write(1, displ[line_no], line_ln[line_no]);
 55             else
 56                 fprintf(stderr, "Bad Line Number\n");
 57         }
 58     }
 59 }