From 9117b283255a6c1c6645c70b1ffd42f28d18c8c8 Mon Sep 17 00:00:00 2001
From: sinanmohd <pcmsinan@gmail.com>
Date: Fri, 24 Jun 2022 19:40:45 +0530
Subject: 5.13

---
 5.13.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 5.13.c

diff --git a/5.13.c b/5.13.c
new file mode 100644
index 0000000..f704f53
--- /dev/null
+++ b/5.13.c
@@ -0,0 +1,103 @@
+/*****************************************************************************
+
+tail
+
+DESCRIPTION: tail prints the last -n lines of a input, if n is not give it 
+prints 10 lines by default, no malloc or stcpy is used in this version and 
+stack storage is allocated in the most efficent way for each line
+
+*****************************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+#define DEFAULT_N 10
+#define MAXLEN 1000
+#define MAXLINE 5000
+#define BUFFSIZE MAXLEN * MAXLINE
+
+char buff[BUFFSIZE];
+char *lineptr[MAXLINE];
+int buff_now;
+int lineptr_now;
+int line_no;
+
+void get_tail(void);
+int sneed_getline(char str[], int max);
+void pr_tail(int nlines);
+
+int 
+main(int argc, char **argv)
+{
+  int nlines = 0;
+
+  if (--argc == 1 && **(++argv) == '-' && isdigit(*++*argv)) {
+    for (; isdigit(**argv) ; ++*argv)
+      nlines = nlines * 10 + **argv - '0';
+  } 
+  
+  else if (argc != 0)
+    argc = -1;
+
+    
+  if (!nlines)
+    nlines = DEFAULT_N;
+
+  if ( argc >= 0 && nlines > 0 && nlines < MAXLINE) {
+    get_tail();
+    pr_tail(nlines);
+  }
+
+  else 
+    printf("Usage: tail -n\n");
+}
+
+void 
+get_tail(void) {
+  int len;
+
+  while ((len = sneed_getline(buff + buff_now, MAXLEN)) > 0) {
+
+    lineptr[lineptr_now] = buff + buff_now ;
+    line_no++;
+    
+    buff_now = (buff_now + MAXLEN >= BUFFSIZE -1) ? 0 : buff_now + len + 1;
+    lineptr_now = (lineptr_now >= MAXLINE - 1) ? 0 : lineptr_now + 1;
+  }
+}
+
+void
+pr_tail(int nlines)
+{
+  if (line_no < nlines)
+    nlines = line_no;
+
+  lineptr_now = (lineptr_now - nlines < 0) ? MAXLINE - 1 + lineptr_now - nlines : lineptr_now - nlines;
+
+  while(nlines--) {
+    printf("%s", lineptr[lineptr_now]);
+    lineptr_now = (lineptr_now >= MAXLINE - 1) ? 0 : lineptr_now + 1;
+  }
+}
+
+int 
+sneed_getline(char str[], int max)
+{
+  char input;
+  char *str_og;
+
+  str_og = str;
+
+  --max;
+  while (--max && (input = getchar()) != EOF && input != '\n')
+    *str++ = input;
+
+  if (input == '\n' && max)
+    *str++ = input;
+
+  *str = '\0';
+
+  return str - str_og;
+}
+
-- 
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