initial population

8 files changed, 1556 insertions, 0 deletions

diff --git a/usr.bin/tail/extern.h b/usr.bin/tail/extern.h
new file mode 100644
index 0000000..24507b7
--- /dev/null
+++ b/usr.bin/tail/extern.h
@@ -0,0 +1,52 @@
+/*	$NetBSD: extern.h,v 1.10 2011/09/03 09:02:20 christos Exp $	*/
+
+/*-
+ * Copyright (c) 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)extern.h	8.1 (Berkeley) 6/6/93
+ */
+
+#define	WR(p, size) \
+	if (write(STDOUT_FILENO, p, size) != size) \
+		oerr();
+
+enum STYLE { NOTSET = 0, FBYTES, FLINES, RBYTES, RLINES, REVERSE };
+
+void forward(FILE *, enum STYLE, off_t, struct stat *);
+void reverse(FILE *, enum STYLE, off_t, struct stat *);
+
+int displaybytes(FILE *, off_t);
+int displaylines(FILE *, off_t);
+
+void xerr(int fatal, const char *fmt, ...) __printflike(2, 3);
+void xerrx(int fatal, const char *fmt, ...) __printflike(2, 3);
+void ierr(void);
+void oerr(void);
+
+extern int fflag, rflag, rval;
+extern const char *fname;
diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c
new file mode 100644
index 0000000..e57e8b5
--- /dev/null
+++ b/usr.bin/tail/forward.c
@@ -0,0 +1,355 @@
+/*	$NetBSD: forward.c,v 1.33 2015/10/09 17:51:26 christos Exp $	*/
+
+/*-
+ * Copyright (c) 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Sze-Tyan Wang.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)forward.c	8.1 (Berkeley) 6/6/93";
+#endif
+__RCSID("$NetBSD: forward.c,v 1.33 2015/10/09 17:51:26 christos Exp $");
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/mman.h>
+#include <sys/event.h>
+
+#include <limits.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "extern.h"
+
+static int rlines(FILE *, off_t, struct stat *);
+
+/* defines for inner loop actions */
+#define	USE_SLEEP	0
+#define	USE_KQUEUE	1
+#define	ADD_EVENTS	2
+
+/*
+ * forward -- display the file, from an offset, forward.
+ *
+ * There are eight separate cases for this -- regular and non-regular
+ * files, by bytes or lines and from the beginning or end of the file.
+ *
+ * FBYTES	byte offset from the beginning of the file
+ *	REG	seek
+ *	NOREG	read, counting bytes
+ *
+ * FLINES	line offset from the beginning of the file
+ *	REG	read, counting lines
+ *	NOREG	read, counting lines
+ *
+ * RBYTES	byte offset from the end of the file
+ *	REG	seek
+ *	NOREG	cyclically read characters into a wrap-around buffer
+ *
+ * RLINES
+ *	REG	mmap the file and step back until reach the correct offset.
+ *	NOREG	cyclically read lines into a wrap-around array of buffers
+ */
+void
+forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
+{
+	int ch, n;
+	int kq=-1, action=USE_SLEEP;
+	struct stat statbuf;
+	struct kevent ev[2];
+
+	switch(style) {
+	case FBYTES:
+		if (off == 0)
+			break;
+		if (S_ISREG(sbp->st_mode)) {
+			if (sbp->st_size < off)
+				off = sbp->st_size;
+			if (fseeko(fp, off, SEEK_SET) == -1) {
+				ierr();
+				return;
+			}
+		} else while (off--)
+			if ((ch = getc(fp)) == EOF) {
+				if (ferror(fp)) {
+					ierr();
+					return;
+				}
+				break;
+			}
+		break;
+	case FLINES:
+		if (off == 0)
+			break;
+		for (;;) {
+			if ((ch = getc(fp)) == EOF) {
+				if (ferror(fp)) {
+					ierr();
+					return;
+				}
+				break;
+			}
+			if (ch == '\n' && !--off)
+				break;
+		}
+		break;
+	case RBYTES:
+		if (S_ISREG(sbp->st_mode)) {
+			if (sbp->st_size >= off &&
+			    fseeko(fp, -off, SEEK_END) == -1) {
+				ierr();
+				return;
+			}
+		} else if (off == 0) {
+			while (getc(fp) != EOF);
+			if (ferror(fp)) {
+				ierr();
+				return;
+			}
+		} else {
+			if (displaybytes(fp, off))
+				return;
+		}
+		break;
+	case RLINES:
+		if (S_ISREG(sbp->st_mode)) {
+			if (!off) {
+				if (fseek(fp, 0L, SEEK_END) == -1) {
+					ierr();
+					return;
+				}
+			} else {
+				if (rlines(fp, off, sbp))
+					return;
+			}
+		} else if (off == 0) {
+			while (getc(fp) != EOF);
+			if (ferror(fp)) {
+				ierr();
+				return;
+			}
+		} else {
+			if (displaylines(fp, off))
+				return;
+		}
+		break;
+	default:
+		break;
+	}
+
+	if (fflag) {
+		kq = kqueue();
+		if (kq < 0)
+			xerr(1, "kqueue");
+		action = ADD_EVENTS;
+	}
+
+	for (;;) {
+		while ((ch = getc(fp)) != EOF)  {
+			if (putchar(ch) == EOF)
+				oerr();
+		}
+		if (ferror(fp)) {
+			ierr();
+			return;
+		}
+		(void)fflush(stdout);
+		if (!fflag)
+			break;
+
+		clearerr(fp);
+
+		switch (action) {
+		case ADD_EVENTS:
+			n = 0;
+
+			memset(ev, 0, sizeof(ev));
+			if (fflag == 2 && fp != stdin) {
+				EV_SET(&ev[n], fileno(fp), EVFILT_VNODE,
+				    EV_ADD | EV_ENABLE | EV_CLEAR,
+				    NOTE_DELETE | NOTE_RENAME, 0, 0);
+				n++;
+			}
+			EV_SET(&ev[n], fileno(fp), EVFILT_READ,
+			    EV_ADD | EV_ENABLE, 0, 0, 0);
+			n++;
+
+			if (kevent(kq, ev, n, NULL, 0, NULL) == -1) {
+				close(kq);
+				kq = -1;
+				action = USE_SLEEP;
+			} else {
+				action = USE_KQUEUE;
+			}
+			break;
+
+		case USE_KQUEUE:
+			if (kevent(kq, NULL, 0, ev, 1, NULL) == -1)
+				xerr(1, "kevent");
+
+			if (ev[0].filter == EVFILT_VNODE) {
+				/* file was rotated, wait until it reappears */
+				action = USE_SLEEP;
+			} else if (ev[0].data < 0) {
+				/* file shrank, reposition to end */
+				if (fseek(fp, 0L, SEEK_END) == -1) {
+					ierr();
+					return;
+				}
+			}
+			break;
+
+		case USE_SLEEP:
+			/*
+			 * We pause for one second after displaying any data
+			 * that has accumulated since we read the file.
+			 */
+                	(void) sleep(1);
+
+			if (fflag == 2 && fp != stdin &&
+			    stat(fname, &statbuf) != -1) {
+				if (statbuf.st_ino != sbp->st_ino ||
+				    statbuf.st_dev != sbp->st_dev ||
+				    statbuf.st_rdev != sbp->st_rdev ||
+				    statbuf.st_nlink == 0) {
+					fp = freopen(fname, "r", fp);
+					if (fp == NULL) {
+						ierr();
+						goto out;
+					}
+					*sbp = statbuf;
+					if (kq != -1)
+						action = ADD_EVENTS;
+				} else if (kq != -1)
+					action = USE_KQUEUE;
+			}
+			break;
+		}
+	}
+out:
+	if (fflag && kq != -1)
+		close(kq);
+}
+
+/*
+ * rlines -- display the last offset lines of the file.
+ *
+ * Non-zero return means than a (non-fatal) error occurred.
+ */
+static int
+rlines(FILE *fp, off_t off, struct stat *sbp)
+{
+	off_t file_size;
+	off_t file_remaining;
+	char *p = NULL;
+	char *start = NULL;
+	off_t mmap_size;
+	off_t mmap_offset;
+	off_t mmap_remaining = 0;
+
+#define MMAP_MAXSIZE  (10 * 1024 * 1024)
+
+	if (!(file_size = sbp->st_size))
+		return 0;
+	file_remaining = file_size;
+
+	if (file_remaining > MMAP_MAXSIZE) {
+		mmap_size = MMAP_MAXSIZE;
+		mmap_offset = file_remaining - MMAP_MAXSIZE;
+	} else {
+		mmap_size = file_remaining;
+		mmap_offset = 0;
+	}
+
+	while (off) {
+		start = mmap(NULL, (size_t)mmap_size, PROT_READ,
+			     MAP_FILE|MAP_SHARED, fileno(fp), mmap_offset);
+		if (start == MAP_FAILED) {
+			xerr(0, "%s", fname);
+			return 1;
+		}
+
+		mmap_remaining = mmap_size;
+		/* Last char is special, ignore whether newline or not. */
+		for (p = start + mmap_remaining - 1 ; --mmap_remaining ; )
+			if (*--p == '\n' && !--off) {
+				++p;
+				break;
+			}
+
+		file_remaining -= mmap_size - mmap_remaining;
+
+		if (off == 0)
+			break;
+
+		if (file_remaining == 0)
+			break;
+
+		if (munmap(start, mmap_size)) {
+			xerr(0, "%s", fname);
+			return 1;
+		}
+
+		if (mmap_offset >= MMAP_MAXSIZE) {
+			mmap_offset -= MMAP_MAXSIZE;
+		} else {
+			mmap_offset = 0;
+			mmap_size = file_remaining;
+		}
+	}
+
+	/*
+	 * Output the (perhaps partial) data in this mmap'd block.
+	 */
+	WR(p, mmap_size - mmap_remaining);
+	file_remaining += mmap_size - mmap_remaining;
+	if (munmap(start, mmap_size)) {
+		xerr(0, "%s", fname);
+		return 1;
+	}
+
+	/*
+	 * Set the file pointer to reflect the length displayed.
+	 * This will cause the caller to redisplay the data if/when
+	 * needed.
+	 */
+	if (fseeko(fp, file_remaining, SEEK_SET) == -1) {
+		ierr();
+		return 1;
+	}
+	return 0;
+}
diff --git a/usr.bin/tail/misc.c b/usr.bin/tail/misc.c
new file mode 100644
index 0000000..0af8f68
--- /dev/null
+++ b/usr.bin/tail/misc.c
@@ -0,0 +1,89 @@
+/*-
+ * Copyright (c) 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Sze-Tyan Wang.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)misc.c	8.1 (Berkeley) 6/6/93";
+#endif
+__RCSID("$NetBSD: misc.c,v 1.7 2011/09/03 09:02:20 christos Exp $");
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <err.h>
+
+#include "extern.h"
+
+void
+ierr(void)
+{
+	xerr(0, "%s", fname);
+}
+
+void
+oerr(void)
+{
+	xerr(1, "stdout");
+}
+
+void
+xerr(int fatal, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vwarn(fmt, ap);
+	va_end(ap);
+	if (fatal)
+		exit(1);
+	rval = 1;
+}
+
+void
+xerrx(int fatal, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vwarnx(fmt, ap);
+	va_end(ap);
+	if (fatal)
+		exit(1);
+	rval = 1;
+}
diff --git a/usr.bin/tail/read.c b/usr.bin/tail/read.c
new file mode 100644
index 0000000..4e9374d
--- /dev/null
+++ b/usr.bin/tail/read.c
@@ -0,0 +1,210 @@
+/*	$NetBSD: read.c,v 1.17 2011/09/03 10:59:10 christos Exp $	*/
+
+/*-
+ * Copyright (c) 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Sze-Tyan Wang.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)read.c	8.1 (Berkeley) 6/6/93";
+#endif
+__RCSID("$NetBSD: read.c,v 1.17 2011/09/03 10:59:10 christos Exp $");
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "extern.h"
+
+/*
+ * displaybytes -- read bytes to an offset from the end and display.
+ *
+ * This is the function that reads to a byte offset from the end of the input,
+ * storing the data in a wrap-around buffer which is then displayed.  If the
+ * rflag is set, the data is displayed in lines in reverse order, and this
+ * routine has the usual nastiness of trying to find the newlines.  Otherwise,
+ * it is displayed from the character closest to the beginning of the input to
+ * the end.
+ *
+ * Non-zero return means than a (non-fatal) error occurred.
+ */
+int
+displaybytes(FILE *fp, off_t off)
+{
+	int ch, len, tlen;
+	char *ep, *p, *t;
+	int wrap;
+	char *sp;
+
+	if ((sp = p = malloc(off)) == NULL)
+		xerr(1, "malloc");
+
+	for (wrap = 0, ep = p + off; (ch = getc(fp)) != EOF;) {
+		*p = ch;
+		if (++p == ep) {
+			wrap = 1;
+			p = sp;
+		}
+	}
+	if (ferror(fp)) {
+		ierr();
+		return 1;
+	}
+
+	if (rflag) {
+		for (t = p - 1, len = 0; t >= sp; --t, ++len)
+			if (*t == '\n' && len) {
+				WR(t + 1, len);
+				len = 0;
+		}
+		if (wrap) {
+			tlen = len;
+			for (t = ep - 1, len = 0; t >= p; --t, ++len)
+				if (*t == '\n') {
+					if (len) {
+						WR(t + 1, len);
+						len = 0;
+					}
+					if (tlen) {
+						WR(sp, tlen);
+						tlen = 0;
+					}
+				}
+			if (len)
+				WR(t + 1, len);
+			if (tlen)
+				WR(sp, tlen);
+		}
+	} else {
+		if (wrap && (len = ep - p))
+			WR(p, len);
+		if ((len = p - sp) != 0)
+			WR(sp, len);
+	}
+	return 0;
+}
+
+/*
+ * displaylines -- read lines to an offset from the end and display.
+ *
+ * This is the function that reads to a line offset from the end of the input,
+ * storing the data in an array of buffers which is then displayed.  If the
+ * rflag is set, the data is displayed in lines in reverse order, and this
+ * routine has the usual nastiness of trying to find the newlines.  Otherwise,
+ * it is displayed from the line closest to the beginning of the input to
+ * the end.
+ *
+ * Non-zero return means than a (non-fatal) error occurred.
+ */
+int
+displaylines(FILE *fp, off_t off)
+{
+	struct {
+		int blen;
+		int len;
+		char *l;
+	} *lines;
+	int ch;
+	char *p;
+	int blen, cnt, recno, wrap;
+	char *sp, *n;
+
+	p = NULL;
+	if ((lines = malloc(off * sizeof(*lines))) == NULL)
+		xerr(1, "malloc");
+
+	memset(lines, 0, sizeof(*lines) * off);
+
+	sp = NULL;
+	blen = cnt = recno = wrap = 0;
+
+	while ((ch = getc(fp)) != EOF) {
+		if (++cnt > blen) {
+			if ((n = realloc(sp, blen + 1024)) == NULL)
+				xerr(1, "realloc");
+			sp = n;
+			blen += 1024;
+			p = sp + cnt - 1;
+		}
+		*p++ = ch;
+		if (ch == '\n') {
+			if (lines[recno].blen < cnt) {
+				if ((n = realloc(lines[recno].l,
+				    cnt + 256)) == NULL)
+					xerr(1, "realloc");
+				lines[recno].l = n;
+				lines[recno].blen = cnt + 256;
+			}
+			memmove(lines[recno].l, sp, lines[recno].len = cnt);
+			cnt = 0;
+			p = sp;
+			if (++recno == off) {
+				wrap = 1;
+				recno = 0;
+			}
+		}
+	}
+	if (ferror(fp)) {
+		free(lines);
+		ierr();
+		return 1;
+	}
+	if (cnt) {
+		lines[recno].l = sp;
+		lines[recno].len = cnt;
+		if (++recno == off) {
+			wrap = 1;
+			recno = 0;
+		}
+	}
+
+	if (rflag) {
+		for (cnt = recno - 1; cnt >= 0; --cnt)
+			WR(lines[cnt].l, lines[cnt].len);
+		if (wrap)
+			for (cnt = off - 1; cnt >= recno; --cnt)
+				WR(lines[cnt].l, lines[cnt].len);
+	} else {
+		if (wrap)
+			for (cnt = recno; cnt < off; ++cnt)
+				WR(lines[cnt].l, lines[cnt].len);
+		for (cnt = 0; cnt < recno; ++cnt)
+			WR(lines[cnt].l, lines[cnt].len);
+	}
+	free(lines);
+	return 0;
+}
diff --git a/usr.bin/tail/reverse.c b/usr.bin/tail/reverse.c
new file mode 100644
index 0000000..bb8bcd9
--- /dev/null
+++ b/usr.bin/tail/reverse.c
@@ -0,0 +1,269 @@
+/*	$NetBSD: reverse.c,v 1.23 2011/09/03 10:59:11 christos Exp $	*/
+
+/*-
+ * Copyright (c) 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Sze-Tyan Wang.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)reverse.c	8.1 (Berkeley) 6/6/93";
+#endif
+__RCSID("$NetBSD: reverse.c,v 1.23 2011/09/03 10:59:11 christos Exp $");
+#endif /* not lint */
+
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include <limits.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "extern.h"
+
+static void r_buf(FILE *);
+static void r_reg(FILE *, enum STYLE, off_t, struct stat *);
+
+/*
+ * reverse -- display input in reverse order by line.
+ *
+ * There are six separate cases for this -- regular and non-regular
+ * files by bytes, lines or the whole file.
+ *
+ * BYTES	display N bytes
+ *	REG	mmap the file and display the lines
+ *	NOREG	cyclically read characters into a wrap-around buffer
+ *
+ * LINES	display N lines
+ *	REG	mmap the file and display the lines
+ *	NOREG	cyclically read lines into a wrap-around array of buffers
+ *
+ * FILE		display the entire file
+ *	REG	mmap the file and display the lines
+ *	NOREG	cyclically read input into a linked list of buffers
+ */
+void
+reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
+{
+	if (style != REVERSE && off == 0)
+		return;
+
+	if (S_ISREG(sbp->st_mode))
+		r_reg(fp, style, off, sbp);
+	else
+		switch(style) {
+		case FBYTES:
+		case RBYTES:
+			(void)displaybytes(fp, off);
+			break;
+		case FLINES:
+		case RLINES:
+			(void)displaylines(fp, off);
+			break;
+		case REVERSE:
+			r_buf(fp);
+			break;
+		default:
+			break;
+		}
+}
+
+/*
+ * r_reg -- display a regular file in reverse order by line.
+ */
+static void
+r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
+{
+	off_t size;
+	int llen;
+	char *p;
+	char *start;
+
+	if (!(size = sbp->st_size))
+		return;
+
+	if ((uint64_t)size > SIZE_T_MAX) {
+			/* XXX: need a cleaner way to check this on amd64 */
+		errno = EFBIG;
+		xerr(0, "%s", fname);
+		return;
+	}
+
+	if ((start = mmap(NULL, (size_t)size, PROT_READ,
+	    MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == MAP_FAILED) {
+		xerr(0, "%s", fname);
+		return;
+	}
+	p = start + size - 1;
+
+	if (style == RBYTES && off < size)
+		size = off;
+
+	/* Last char is special, ignore whether newline or not. */
+	for (llen = 1; --size; ++llen)
+		if (*--p == '\n') {
+			WR(p + 1, llen);
+			llen = 0;
+			if (style == RLINES && !--off) {
+				++p;
+				break;
+			}
+		}
+	if (llen)
+		WR(p, llen);
+	if (munmap(start, (size_t)sbp->st_size))
+		xerr(0, "%s", fname);
+}
+
+typedef struct bf {
+	struct bf *next;
+	struct bf *prev;
+	int len;
+	char *l;
+} BF;
+
+/*
+ * r_buf -- display a non-regular file in reverse order by line.
+ *
+ * This is the function that saves the entire input, storing the data in a
+ * doubly linked list of buffers and then displays them in reverse order.
+ * It has the usual nastiness of trying to find the newlines, as there's no
+ * guarantee that a newline occurs anywhere in the file, let alone in any
+ * particular buffer.  If we run out of memory, input is discarded (and the
+ * user warned).
+ */
+static void
+r_buf(FILE *fp)
+{
+	BF *mark, *tl, *tr;
+	int ch, len, llen;
+	char *p;
+	off_t enomem;
+
+#define	BSZ	(128 * 1024)
+	tl =  NULL;
+	for (mark = NULL, enomem = 0;;) {
+		/*
+		 * Allocate a new block and link it into place in a doubly
+		 * linked list.  If out of memory, toss the LRU block and
+		 * keep going.
+		 */
+		if (enomem) {
+			if (!mark) {
+				errno = ENOMEM;
+				xerr(1, NULL);
+			}
+			tl = tl->next;
+			enomem += tl->len;
+		} else if ((tl = malloc(sizeof(*tl))) == NULL ||
+		    (tl->l = malloc(BSZ)) == NULL) {
+			if (tl)
+				free(tl);
+			if (!mark) {
+				errno = ENOMEM;
+				xerr(1, NULL);
+			}
+			tl = mark;
+			enomem += tl->len;
+		} else if (mark) {
+			tl->next = mark;
+			tl->prev = mark->prev;
+			mark->prev->next = tl;
+			mark->prev = tl;
+		} else {
+			mark = tl;
+			mark->next = mark->prev = mark;
+		}
+
+		/* Fill the block with input data. */
+		ch = 0;
+		for (p = tl->l, len = 0;
+		    len < BSZ && (ch = getc(fp)) != EOF; ++len)
+			*p++ = ch;
+
+		/*
+		 * If no input data for this block and we tossed some data,
+		 * recover it.
+		 */
+		if (!len) {
+			if (enomem)
+				enomem -= tl->len;
+			tl = tl->prev;
+			break;
+		}
+
+		tl->len = len;
+		if (ch == EOF)
+			break;
+	}
+
+	if (enomem) {
+		xerrx(0, "Warning: %lld bytes discarded", (long long)enomem);
+	}
+
+	/*
+	 * Step through the blocks in the reverse order read.  The last char
+	 * is special, ignore whether newline or not.
+	 */
+	for (mark = tl;;) {
+		for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
+		    --p, ++llen)
+			if (*p == '\n') {
+				if (llen) {
+					WR(p + 1, llen);
+					llen = 0;
+				}
+				if (tl == mark)
+					continue;
+				for (tr = tl->next; tr->len; tr = tr->next) {
+					WR(tr->l, tr->len);
+					tr->len = 0;
+					if (tr == mark)
+						break;
+				}
+			}
+		tl->len = llen;
+		if ((tl = tl->prev) == mark)
+			break;
+	}
+	tl = tl->next;
+	if (tl->len) {
+		WR(tl->l, tl->len);
+		tl->len = 0;
+	}
+	while ((tl = tl->next)->len) {
+		WR(tl->l, tl->len);
+		tl->len = 0;
+	}
+}
diff --git a/usr.bin/tail/tac.1 b/usr.bin/tail/tac.1
new file mode 100644
index 0000000..d0dd1e8
--- /dev/null
+++ b/usr.bin/tail/tac.1
@@ -0,0 +1,56 @@
+.\"	$NetBSD: tac.1,v 1.2 2017/10/01 22:35:23 kre Exp $
+.\"
+.\" Copyright (c) 2017 The NetBSD Foundation, Inc.
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to The NetBSD Foundation
+.\" by Maya Rashish.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\"
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in
+.\"    the documentation and/or other materials provided with the
+.\"    distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
+.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd October 1, 2017
+.Dt TAC 1
+.Os
+.Sh NAME
+.Nm tac
+.Nd display file in reverse
+.Sh SYNOPSIS
+.Nm
+.Op Ar file ...
+.Sh DESCRIPTION
+.Nm
+.Pq cat backwards
+outputs the contents of each of each of the specified files,
+or the standard input if no files are specified,
+in reverse line order to the standard output.
+.Sh EXIT STATUS
+.Ex -std tac
+.Sh COMPATIBILITY
+The
+.Nm
+utility doesn't support any of the options of GNU tac.
+.Sh SEE ALSO
+.Xr cat 1 ,
+.Xr tail 1
diff --git a/usr.bin/tail/tail.1 b/usr.bin/tail/tail.1
new file mode 100644
index 0000000..1a68f88
--- /dev/null
+++ b/usr.bin/tail/tail.1
@@ -0,0 +1,202 @@
+.\"	$NetBSD: tail.1,v 1.20 2017/10/15 03:57:47 pgoyette Exp $
+.\"
+.\" Copyright (c) 1980, 1990, 1991, 1993
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" the Institute of Electrical and Electronics Engineers, Inc.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"	@(#)tail.1	8.1 (Berkeley) 6/6/93
+.\"
+.Dd October 1, 2017
+.Dt TAIL 1
+.Os
+.Sh NAME
+.Nm tail
+.Nd display the last part of a file
+.Sh SYNOPSIS
+.Nm
+.Fl qv
+.Oo
+.Fl f |
+.Fl F |
+.Fl r
+.Oc
+.Oo
+.Fl b Ar number |
+.Fl c Ar number |
+.Fl n Ar number
+.Oc
+.Op Ar file ...
+.Sh DESCRIPTION
+The
+.Nm
+utility displays the contents of
+.Ar file
+or, by default, its standard input, to the standard output.
+.Pp
+The display begins at a byte, line or 512-byte block location in the
+input.
+Numbers having a leading plus (``+'') sign are relative to the beginning
+of the input, for example,
+.Dq -c +2
+starts the display at the second
+byte of the input.
+Numbers having a leading minus (``-'') sign or no explicit sign are
+relative to the end of the input, for example,
+.Dq -n 2
+displays the last two lines of the input.
+The default starting location is
+.Dq -n 10 ,
+or the last 10 lines of the input.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl b Ar number
+The location is
+.Ar number
+512-byte blocks.
+.It Fl c Ar number
+The location is
+.Ar number
+bytes.
+.It Fl f
+The
+.Fl f
+option causes
+.Nm
+not to stop when end of file is reached, but rather to wait for additional
+data to be appended to the input.
+The
+.Fl f
+option is ignored if there are no file arguments and the standard
+input is a pipe or a FIFO.
+.It Fl F
+The
+.Fl F
+option is the same as the
+.Fl f
+option, except that every five seconds
+.Nm
+will check to see if the file named on the command line has been
+shortened or moved (it is considered moved if the inode or device
+number changes) and, if so, it will close
+the current file, open the filename given, print out the entire
+contents, and continue to wait for more data to be appended.
+This option is used to follow log files though rotation by
+.Xr newsyslog 8
+or similar programs.
+.It Fl n Ar number
+The location is
+.Ar number
+lines.
+.It Fl q
+Do not prepend a header for each file, even if multiple files
+are specified.
+.It Fl r
+The
+.Fl r
+option causes the input to be displayed in reverse order, by line.
+Additionally, this option changes the meaning of the
+.Fl b ,
+.Fl c
+and
+.Fl n
+options.
+When the
+.Fl r
+option is specified, these options specify the number of bytes, lines
+or 512-byte blocks to display, instead of the bytes, lines or blocks
+from the beginning or end of the input from which to begin the display.
+The default for the
+.Fl r
+option is to display all of the input.
+.It Fl v
+Prepend each file with a header.
+.El
+.Pp
+If more than a single file is specified, or the
+.Fl v
+option is used, each file is preceded by a
+header consisting of the string
+.Dq ==> XXX \*[Le]=
+where
+.Dq XXX
+is the name of the file.
+The
+.Fl q
+flag disables the printing of the header in all cases.
+.Sh EXIT STATUS
+.Ex -std tail
+.Sh SEE ALSO
+.Xr cat 1 ,
+.Xr head 1 ,
+.Xr sed 1
+.Sh STANDARDS
+The
+.Nm
+utility is expected to be a superset of the
+.St -p1003.2-92
+specification.
+In particular, the
+.Fl b ,
+.Fl r
+and
+.Fl F
+options are extensions to that standard.
+.Pp
+The historic command line syntax of
+.Nm
+is supported by this implementation.
+The only difference between this implementation and historic versions
+of
+.Nm ,
+once the command line syntax translation has been done, is that the
+.Fl b ,
+.Fl c
+and
+.Fl n
+options modify the
+.Fl r
+option, i.e., ``-r -c 4'' displays the last 4 characters of the last line
+of the input, while the historic tail (using the historic syntax ``-4cr'')
+would ignore the
+.Fl c
+option and display the last 4 lines of the input.
+.Sh HISTORY
+A
+.Nm
+command appeared in
+.At v7 .
+.Sh BUGS
+When using the
+.Fl F
+option,
+.Nm
+will not detect a file truncation if, between the truncation
+and the next check of the file size, data written to the file make
+it larger than the last known file size.
diff --git a/usr.bin/tail/tail.c b/usr.bin/tail/tail.c
new file mode 100644
index 0000000..dff9559
--- /dev/null
+++ b/usr.bin/tail/tail.c
@@ -0,0 +1,323 @@
+/*-
+ * Copyright (c) 1991, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Sze-Tyan Wang.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+__COPYRIGHT("@(#) Copyright (c) 1991, 1993\
+ The Regents of the University of California.  All rights reserved.");
+#endif /* not lint */
+
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
+#endif
+__RCSID("$NetBSD: tail.c,v 1.20 2018/03/06 03:33:26 eadler Exp $");
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "extern.h"
+
+int fflag, rflag, rval;
+const char *fname;
+
+static void obsolete(char **);
+static void usage(void) __dead;
+
+int
+main(int argc, char *argv[])
+{
+	struct stat sb;
+	FILE *fp;
+	off_t off;
+	enum STYLE style;
+	int ch, first;
+	char *p;
+	int qflag = 0;
+	int vflag = 0;
+
+	setprogname(argv[0]);
+	off = 0;
+	/*
+	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
+	 * -n+10.  Second, the number options are 1 based and not offsets,
+	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
+	 * number options for the -r option specify the number of things that
+	 * get displayed, not the starting point in the file.  The one major
+	 * incompatibility in this version as compared to historical versions
+	 * is that the 'r' option couldn't be modified by the -lbc options,
+	 * i.e., it was always done in lines.  This version treats -rc as a
+	 * number of characters in reverse order.  Finally, the default for
+	 * -r is the entire file, not 10 lines.
+	 */
+#define	ARG(units, forward, backward) {					\
+	if (style)							\
+		usage();						\
+	off = strtoll(optarg, &p, 10) * (units);			\
+	if (*p)								\
+		xerrx(1, "illegal offset -- %s", optarg);		\
+	switch(optarg[0]) {						\
+	case '+':							\
+		if (off)						\
+			off -= (units);					\
+			style = (forward);				\
+		break;							\
+	case '-':							\
+		off = -off;						\
+		/* FALLTHROUGH */					\
+	default:							\
+		style = (backward);					\
+		break;							\
+	}								\
+}
+
+	obsolete(argv);
+	style = NOTSET;
+	if (strcmp(getprogname(), "tac") == 0) {
+		qflag = 1;
+		vflag = 0;
+		rflag = 1;
+		argc -= 1;
+		argv += 1;
+	} else { /* tail */
+		while ((ch = getopt(argc, argv, "Fb:c:fn:rqv")) != -1)
+			switch(ch) {
+			case 'F':
+				fflag = 2;
+				break;
+			case 'b':
+				ARG(512, FBYTES, RBYTES);
+				break;
+			case 'c':
+				ARG(1, FBYTES, RBYTES);
+				break;
+			case 'f':
+				fflag = 1;
+				break;
+			case 'n':
+				ARG(1, FLINES, RLINES);
+				break;
+			case 'r':
+				rflag = 1;
+				break;
+			case 'q':
+				qflag = 1;
+				vflag = 0;
+				break;
+			case 'v':
+				qflag = 0;
+				vflag = 1;
+				break;
+			case '?':
+			default:
+				usage();
+			}
+		argc -= optind;
+		argv += optind;
+	}
+
+	if (fflag && argc > 1)
+		xerrx(1,
+		    "-f and -F options only appropriate for a single file");
+
+	/*
+	 * If displaying in reverse, don't permit follow option, and convert
+	 * style values.
+	 */
+	if (rflag) {
+		if (fflag)
+			usage();
+		if (style == FBYTES)
+			style = RBYTES;
+		else if (style == FLINES)
+			style = RLINES;
+	}
+
+	/*
+	 * If style not specified, the default is the whole file for -r, and
+	 * the last 10 lines if not -r.
+	 */
+	if (style == NOTSET) {
+		if (rflag) {
+			off = 0;
+			style = REVERSE;
+		} else {
+			off = 10;
+			style = RLINES;
+		}
+	}
+	if (*argv)
+		for (first = 1; (fname = *argv++) != NULL;) {
+			if ((fp = fopen(fname, "r")) == NULL ||
+			    fstat(fileno(fp), &sb)) {
+				ierr();
+				continue;
+			}
+			if (vflag || (qflag == 0 && argc > 1)) {
+				(void)printf("%s==> %s <==\n",
+				    first ? "" : "\n", fname);
+				first = 0;
+				(void)fflush(stdout);
+			}
+
+			if (rflag)
+				reverse(fp, style, off, &sb);
+			else
+				forward(fp, style, off, &sb);
+			(void)fclose(fp);
+		}
+	else {
+		fname = "stdin";
+
+		if (fstat(fileno(stdin), &sb)) {
+			ierr();
+			exit(1);
+		}
+
+		/*
+		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
+		 * bit in the st_mode field for pipes.  Fix this then.
+		 */
+		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
+		    errno == ESPIPE) {
+			errno = 0;
+			fflag = 0;		/* POSIX.2 requires this. */
+		}
+
+		if (rflag)
+			reverse(stdin, style, off, &sb);
+		else
+			forward(stdin, style, off, &sb);
+	}
+	exit(rval);
+}
+
+/*
+ * Convert the obsolete argument form into something that getopt can handle.
+ * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't
+ * the option argument for a -b, -c or -n option gets converted.
+ */
+static void
+obsolete(char *argv[])
+{
+	char *ap, *p, *t;
+	size_t len;
+	char *start;
+
+	while ((ap = *++argv) != NULL) {
+		/* Return if "--" or not an option of any form. */
+		if (ap[0] != '-') {
+			if (ap[0] != '+')
+				return;
+		} else if (ap[1] == '-')
+			return;
+
+		switch (*++ap) {
+		/* Old-style option. */
+		case '0': case '1': case '2': case '3': case '4':
+		case '5': case '6': case '7': case '8': case '9':
+
+			/* Malloc space for dash, new option and argument. */
+			len = strlen(*argv);
+			if ((start = p = malloc(len + 3)) == NULL)
+				xerr(1, "malloc");
+			*p++ = '-';
+
+			/*
+			 * Go to the end of the option argument.  Save off any
+			 * trailing options (-3lf) and translate any trailing
+			 * output style characters.
+			 */
+			t = *argv + len - 1;
+			if (*t == 'f' || *t == 'r') {
+				*p++ = *t;
+				*t-- = '\0';
+			}
+			switch(*t) {
+			case 'b':
+				*p++ = 'b';
+				*t = '\0';
+				break;
+			case 'c':
+				*p++ = 'c';
+				*t = '\0';
+				break;
+			case 'l':
+				*t = '\0';
+				/* FALLTHROUGH */
+			case '0': case '1': case '2': case '3': case '4':
+			case '5': case '6': case '7': case '8': case '9':
+				*p++ = 'n';
+				break;
+			default:
+				xerrx(1, "illegal option -- %s", *argv);
+			}
+			*p++ = *argv[0];
+			(void)strcpy(p, ap);
+			*argv = start;
+			continue;
+
+		/*
+		 * Options w/ arguments, skip the argument and continue
+		 * with the next option.
+		 */
+		case 'b':
+		case 'c':
+		case 'n':
+			if (!ap[1])
+				++argv;
+			/* FALLTHROUGH */
+		/* Options w/o arguments, continue with the next option. */
+		case 'f':
+		case 'r':
+			continue;
+
+		/* Illegal option, return and let getopt handle it. */
+		default:
+			return;
+		}
+	}
+}
+
+static void
+usage(void)
+{
+	(void)fprintf(stderr,
+	    "Usage: %s [-qv] [-f | -F | -r] [-b # | -c # | -n #] [file ...]\n",
+	    getprogname());
+	exit(1);
+}