add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/tail.c

@@ -0,0 +1,145 @@
+/* tail - print the end of a file */
+
+#include <stdio.h>
+
+#define TRUE 1
+#define FALSE 0
+#define BLANK ' '
+#define TAB '\t'
+#define NEWL '\n'
+
+int lines, chars;
+char buff[BUFSIZ];
+
+main(argc, argv)
+int argc;
+char *argv[];
+{
+  char *s;
+  FILE *input, *fopen();
+  int count;
+
+  setbuf(stdout, buff);
+  argc--;
+  argv++;
+  lines = TRUE;
+  chars = FALSE;
+  count = -10;
+
+  if (argc == 0) {
+	tail(stdin, count);
+	exit(0);
+  }
+  s = *argv;
+  if (*s == '-' || *s == '+') {
+	s++;
+	if (*s >= '0' && *s <= '9') {
+		count = stoi(*argv);
+		s++;
+		while (*s >= '0' && *s <= '9') s++;
+	}
+	if (*s == 'c') {
+		chars = TRUE;
+		lines = FALSE;
+	} else if (*s != 'l' && *s != '\0') {
+		fprintf(stderr, "tail: unknown option %c\n", *s);
+		argc = 0;
+	}
+	argc--;
+	argv++;
+  }
+  if (argc < 0) {
+	fprintf(stderr, "Usage: tail [+/-[number][lc]] [files]\n");
+	exit(1);
+  }
+  if (argc == 0) tail(stdin, count);
+
+  else if ((input = fopen(*argv, "r")) == NULL) {
+	fprintf(stderr, "tail: can't open %s\n", *argv);
+	exit(1);
+  } else {
+	tail(input, count);
+	fclose(input);
+  }
+
+  exit(0);
+}
+
+/* Stoi - convert string to integer */
+stoi(s)
+char *s;
+{
+  int n, sign;
+
+  while (*s == BLANK || *s == NEWL || *s == TAB) s++;
+
+  sign = 1;
+  if (*s == '+')
+	s++;
+  else if (*s == '-') {
+	sign = -1;
+	s++;
+  }
+  for (n = 0; *s >= '0' && *s <= '9'; s++) n = 10 * n + *s - '0';
+  return(sign * n);
+}
+
+/* Tail - print 'count' lines/chars */
+
+#define INCR(p)  if (p >= end) p=cbuf ; else p++
+#define BUF_SIZE 4098
+
+char cbuf[BUF_SIZE];
+
+tail(in, goal)
+FILE *in;
+int goal;
+{
+  int c, count;
+  char *start, *finish, *end;
+
+  count = 0;
+
+  if (goal > 0) {		/* skip */
+	count++;		/* start counting at 1 */
+	if (lines)		/* lines */
+		while ((c = getc(in)) != EOF) {
+			if (c == NEWL) count++;
+			if (count >= goal) break;
+		}
+	else			/* chars */
+		while (getc(in) != EOF) {
+			count++;
+			if (count >= goal) break;
+		}
+	if (count >= goal) while ((c = getc(in)) != EOF)
+			putc(c, stdout);
+  } else {			/* tail */
+
+	goal = -goal;
+	start = finish = cbuf;
+	end = &cbuf[BUF_SIZE - 1];
+
+	while ((c = getc(in)) != EOF) {
+		*finish = c;
+		INCR(finish);
+
+		if (start == finish) INCR(start);
+		if (!lines || c == NEWL) count++;
+
+		if (count > goal) {
+			count = goal;
+			if (lines) while (*start != NEWL)
+					INCR(start);
+			INCR(start);
+		}
+	}			/* end while */
+
+	while (start != finish) {
+		putc(*start, stdout);
+		INCR(start);
+	}
+
+  }				/* end else */
+
+}				/* end tail */