ex_5-13.c

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include <ctype.h>
   4 #include <stdlib.h>
   5
   6 #define  DEFLINES 10
   7 #define MAXLENGTH 1000
   8
   9 void error(const char *err)
  10 {
  11         fprintf(stderr, "ERROR: %s\n", err);
  12         exit(EXIT_FAILURE);
  13 }
  14
  15 int getline(char s[], int limit)
  16 {
  17         int i, c;
  18         for(i = 0; i < limit - 1 && (c = getchar()) != EOF && c != '\n'; i++)
  19         {
  20                 s[i] = c;
  21         }
  22                 if(c == '\n'){ s[i++] = c; }
  23         s[i] = '\0';
  24         return i;
  25 }
  26
  27 char *dupstr(const char *in)
  28 {
  29         char *str = malloc(strlen(in)+1);
  30         if(str)
  31         {
  32                 strcpy(str, in);
  33         }
  34         return str;
  35 }
  36
  37 int main(int argc, char *argv[])
  38 {
  39         int i, j, lines = DEFLINES;
  40         char **buff;
  41         char buffer[MAXLENGTH];
  42         if(argc > 1)
  43         {
  44                 lines = atoi(argv[1]);
  45                 lines = -lines; // input as negative - fixed that here
  46                 if(lines < 1) { error("Incorrect Input"); }
  47         }
  48         buff = malloc(sizeof *buff * lines);
  49         if(!buff) { error("Could not allocate enough memory"); }
  50         for(i = 0; i < lines; i++)
  51         {
  52                 buff[i] = NULL;
  53         }
  54
  55         int current_line = 0;
  56         do {
  57                 getline(buffer, sizeof buffer); // get line and store in buffer
  58                 if(!feof(stdin))
  59                 {
  60                         if(buff[current_line])
  61                                 free(buff[current_line]);
  62
  63                         buff[current_line] = dupstr(buffer);
  64                         if(!buff[current_line])
  65                         {
  66                                 error("Out of Memory.");
  67                         }
  68                         current_line = (current_line + 1) % lines;
  69                 }
  70         } while (!feof(stdin));
  71         for( i = 0; i < lines; i++)
  72         {
  73                 j = (current_line + i) % lines;
  74                 if(buff[j])
  75                 {
  76                         printf("%s", buff[j]);
  77                         free(buff[j]);
  78                 }
  79         }
  80         return EXIT_SUCCESS;
  81 }