1/*-
2 * Copyright (c) 1991, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Edward Sze-Tyan Wang.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#include <sys/cdefs.h>
34#ifndef lint
35__COPYRIGHT("@(#) Copyright (c) 1991, 1993\
36 The Regents of the University of California.  All rights reserved.");
37#endif /* not lint */
38
39#ifndef lint
40#if 0
41static char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
42#endif
43__RCSID("$NetBSD: tail.c,v 1.21 2023/08/07 19:11:25 tnn Exp $");
44#endif /* not lint */
45
46#include <sys/types.h>
47#include <sys/stat.h>
48#include <errno.h>
49#include <unistd.h>
50#include <stdio.h>
51#include <stdlib.h>
52#include <string.h>
53#include "extern.h"
54
55int fflag, rflag, rval;
56const char *fname;
57
58static void obsolete(char **);
59static void usage(void) __dead;
60
61int
62main(int argc, char *argv[])
63{
64	struct stat sb;
65	FILE *fp;
66	off_t off;
67	enum STYLE style;
68	int ch, first;
69	char *p;
70	int qflag = 0;
71	int vflag = 0;
72
73	setprogname(argv[0]);
74	off = 0;
75	/*
76	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
77	 * -n+10.  Second, the number options are 1 based and not offsets,
78	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
79	 * number options for the -r option specify the number of things that
80	 * get displayed, not the starting point in the file.  The one major
81	 * incompatibility in this version as compared to historical versions
82	 * is that the 'r' option couldn't be modified by the -lbc options,
83	 * i.e., it was always done in lines.  This version treats -rc as a
84	 * number of characters in reverse order.  Finally, the default for
85	 * -r is the entire file, not 10 lines.
86	 */
87#define	ARG(units, forward, backward) {					\
88	if (style)							\
89		usage();						\
90	off = strtoll(optarg, &p, 10) * (units);			\
91	if (*p)								\
92		xerrx(1, "illegal offset -- %s", optarg);		\
93	switch(optarg[0]) {						\
94	case '+':							\
95		if (off)						\
96			off -= (units);					\
97		style = (forward);					\
98		break;							\
99	case '-':							\
100		off = -off;						\
101		/* FALLTHROUGH */					\
102	default:							\
103		style = (backward);					\
104		break;							\
105	}								\
106}
107
108	obsolete(argv);
109	style = NOTSET;
110	if (strcmp(getprogname(), "tac") == 0) {
111		qflag = 1;
112		vflag = 0;
113		rflag = 1;
114		argc -= 1;
115		argv += 1;
116	} else { /* tail */
117		while ((ch = getopt(argc, argv, "Fb:c:fn:rqv")) != -1)
118			switch(ch) {
119			case 'F':
120				fflag = 2;
121				break;
122			case 'b':
123				ARG(512, FBYTES, RBYTES);
124				break;
125			case 'c':
126				ARG(1, FBYTES, RBYTES);
127				break;
128			case 'f':
129				fflag = 1;
130				break;
131			case 'n':
132				ARG(1, FLINES, RLINES);
133				break;
134			case 'r':
135				rflag = 1;
136				break;
137			case 'q':
138				qflag = 1;
139				vflag = 0;
140				break;
141			case 'v':
142				qflag = 0;
143				vflag = 1;
144				break;
145			case '?':
146			default:
147				usage();
148			}
149		argc -= optind;
150		argv += optind;
151	}
152
153	if (fflag && argc > 1)
154		xerrx(1,
155		    "-f and -F options only appropriate for a single file");
156
157	/*
158	 * If displaying in reverse, don't permit follow option, and convert
159	 * style values.
160	 */
161	if (rflag) {
162		if (fflag)
163			usage();
164		if (style == FBYTES)
165			style = RBYTES;
166		else if (style == FLINES)
167			style = RLINES;
168	}
169
170	/*
171	 * If style not specified, the default is the whole file for -r, and
172	 * the last 10 lines if not -r.
173	 */
174	if (style == NOTSET) {
175		if (rflag) {
176			off = 0;
177			style = REVERSE;
178		} else {
179			off = 10;
180			style = RLINES;
181		}
182	}
183	if (*argv)
184		for (first = 1; (fname = *argv++) != NULL;) {
185			if ((fp = fopen(fname, "r")) == NULL ||
186			    fstat(fileno(fp), &sb)) {
187				ierr();
188				continue;
189			}
190			if (vflag || (qflag == 0 && argc > 1)) {
191				(void)printf("%s==> %s <==\n",
192				    first ? "" : "\n", fname);
193				first = 0;
194				(void)fflush(stdout);
195			}
196
197			if (rflag)
198				reverse(fp, style, off, &sb);
199			else
200				forward(fp, style, off, &sb);
201			(void)fclose(fp);
202		}
203	else {
204		fname = "stdin";
205
206		if (fstat(fileno(stdin), &sb)) {
207			ierr();
208			exit(1);
209		}
210
211		/*
212		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
213		 * bit in the st_mode field for pipes.  Fix this then.
214		 */
215		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
216		    errno == ESPIPE) {
217			errno = 0;
218			fflag = 0;		/* POSIX.2 requires this. */
219		}
220
221		if (rflag)
222			reverse(stdin, style, off, &sb);
223		else
224			forward(stdin, style, off, &sb);
225	}
226	exit(rval);
227}
228
229/*
230 * Convert the obsolete argument form into something that getopt can handle.
231 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't
232 * the option argument for a -b, -c or -n option gets converted.
233 */
234static void
235obsolete(char *argv[])
236{
237	char *ap, *p, *t;
238	size_t len;
239	char *start;
240
241	while ((ap = *++argv) != NULL) {
242		/* Return if "--" or not an option of any form. */
243		if (ap[0] != '-') {
244			if (ap[0] != '+')
245				return;
246		} else if (ap[1] == '-')
247			return;
248
249		switch (*++ap) {
250		/* Old-style option. */
251		case '0': case '1': case '2': case '3': case '4':
252		case '5': case '6': case '7': case '8': case '9':
253
254			/* Malloc space for dash, new option and argument. */
255			len = strlen(*argv);
256			if ((start = p = malloc(len + 3)) == NULL)
257				xerr(1, "malloc");
258			*p++ = '-';
259
260			/*
261			 * Go to the end of the option argument.  Save off any
262			 * trailing options (-3lf) and translate any trailing
263			 * output style characters.
264			 */
265			t = *argv + len - 1;
266			if (*t == 'f' || *t == 'r') {
267				*p++ = *t;
268				*t-- = '\0';
269			}
270			switch(*t) {
271			case 'b':
272				*p++ = 'b';
273				*t = '\0';
274				break;
275			case 'c':
276				*p++ = 'c';
277				*t = '\0';
278				break;
279			case 'l':
280				*t = '\0';
281				/* FALLTHROUGH */
282			case '0': case '1': case '2': case '3': case '4':
283			case '5': case '6': case '7': case '8': case '9':
284				*p++ = 'n';
285				break;
286			default:
287				xerrx(1, "illegal option -- %s", *argv);
288			}
289			*p++ = *argv[0];
290			(void)strcpy(p, ap);
291			*argv = start;
292			continue;
293
294		/*
295		 * Options w/ arguments, skip the argument and continue
296		 * with the next option.
297		 */
298		case 'b':
299		case 'c':
300		case 'n':
301			if (!ap[1])
302				++argv;
303			/* FALLTHROUGH */
304		/* Options w/o arguments, continue with the next option. */
305		case 'f':
306		case 'r':
307			continue;
308
309		/* Illegal option, return and let getopt handle it. */
310		default:
311			return;
312		}
313	}
314}
315
316static void
317usage(void)
318{
319	(void)fprintf(stderr,
320	    "Usage: %s [-qv] [-f | -F | -r] [-b # | -c # | -n #] [file ...]\n",
321	    getprogname());
322	exit(1);
323}
324