1/*	$OpenBSD: tail.c,v 1.24 2022/12/04 23:50:49 cheloha Exp $	*/
2
3/*-
4 * Copyright (c) 1991, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Edward Sze-Tyan Wang.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/types.h>
36#include <sys/stat.h>
37
38#include <err.h>
39#include <errno.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <unistd.h>
44
45#include "extern.h"
46
47int fflag, rflag, rval;
48
49static void obsolete(char **);
50static void usage(void);
51
52int
53main(int argc, char *argv[])
54{
55	struct tailfile *tf;
56	off_t off = 0;
57	enum STYLE style;
58	int ch;
59	int i;
60	char *p;
61
62	if (pledge("stdio rpath", NULL) == -1)
63		err(1, "pledge");
64
65	/*
66	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
67	 * -n+10.  Second, the number options are 1 based and not offsets,
68	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
69	 * number options for the -r option specify the number of things that
70	 * get displayed, not the starting point in the file.  The one major
71	 * incompatibility in this version as compared to historical versions
72	 * is that the 'r' option couldn't be modified by the -lbc options,
73	 * i.e. it was always done in lines.  This version treats -rc as a
74	 * number of characters in reverse order.  Finally, the default for
75	 * -r is the entire file, not 10 lines.
76	 */
77#define	ARG(units, forward, backward) {					\
78	if (style)							\
79		usage();						\
80	off = strtoll(optarg, &p, 10) * (units);			\
81	if (*p)								\
82		errx(1, "illegal offset -- %s", optarg);		\
83	switch(optarg[0]) {						\
84	case '+':							\
85		if (off)						\
86			off -= (units);					\
87		style = (forward);					\
88		break;							\
89	case '-':							\
90		off = -off;						\
91		/* FALLTHROUGH */					\
92	default:							\
93		style = (backward);					\
94		break;							\
95	}								\
96}
97
98	obsolete(argv);
99	style = NOTSET;
100	while ((ch = getopt(argc, argv, "b:c:fn:r")) != -1)
101		switch(ch) {
102		case 'b':
103			ARG(512, FBYTES, RBYTES);
104			break;
105		case 'c':
106			ARG(1, FBYTES, RBYTES);
107			break;
108		case 'f':
109			fflag = 1;
110			break;
111		case 'n':
112			ARG(1, FLINES, RLINES);
113			break;
114		case 'r':
115			rflag = 1;
116			break;
117		default:
118			usage();
119		}
120	argc -= optind;
121	argv += optind;
122
123	/*
124	 * If displaying in reverse, don't permit follow option, and convert
125	 * style values.
126	 */
127	if (rflag) {
128		if (fflag)
129			usage();
130		if (style == FBYTES)
131			style = RBYTES;
132		else if (style == FLINES)
133			style = RLINES;
134	}
135
136	/*
137	 * If style not specified, the default is the whole file for -r, and
138	 * the last 10 lines if not -r.
139	 */
140	if (style == NOTSET) {
141		if (rflag) {
142			off = 0;
143			style = REVERSE;
144		} else {
145			off = 10;
146			style = RLINES;
147		}
148	}
149
150	if ((tf = reallocarray(NULL, argc ? argc : 1, sizeof(*tf))) == NULL)
151		err(1, "reallocarray");
152
153	if (argc) {
154		for (i = 0; *argv; i++) {
155			tf[i].fname = *argv++;
156			if ((tf[i].fp = fopen(tf[i].fname, "r")) == NULL ||
157			    fstat(fileno(tf[i].fp), &(tf[i].sb))) {
158				ierr(tf[i].fname);
159				i--;
160				continue;
161			}
162		}
163		if (rflag)
164			reverse(tf, i, style, off);
165		else
166			forward(tf, i, style, off);
167	}
168	else {
169		if (pledge("stdio", NULL) == -1)
170			err(1, "pledge");
171
172		tf[0].fname = "stdin";
173		tf[0].fp = stdin;
174
175		if (fstat(fileno(stdin), &(tf[0].sb))) {
176			ierr(tf[0].fname);
177			exit(1);
178		}
179
180		/*
181		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
182		 * bit in the st_mode field for pipes.  Fix this then.
183		 */
184		if (lseek(fileno(tf[0].fp), (off_t)0, SEEK_CUR) == -1 &&
185		    errno == ESPIPE) {
186			errno = 0;
187			fflag = 0;		/* POSIX.2 requires this. */
188		}
189
190		if (rflag)
191			reverse(tf, 1, style, off);
192		else
193			forward(tf, 1, style, off);
194	}
195	exit(rval);
196}
197
198/*
199 * Convert the obsolete argument form into something that getopt can handle.
200 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't
201 * the option argument for a -b, -c or -n option gets converted.
202 */
203static void
204obsolete(char *argv[])
205{
206	char *ap, *p, *t;
207	size_t len;
208	char *start;
209
210	while ((ap = *++argv)) {
211		/* Return if "--" or not an option of any form. */
212		if (ap[0] != '-') {
213			if (ap[0] != '+')
214				return;
215		} else if (ap[1] == '-')
216			return;
217
218		switch(*++ap) {
219		/* Old-style option. */
220		case '0': case '1': case '2': case '3': case '4':
221		case '5': case '6': case '7': case '8': case '9':
222
223			/* Malloc space for dash, new option and argument. */
224			len = strlen(*argv);
225			if ((start = p = malloc(len + 4)) == NULL)
226				err(1, NULL);
227			*p++ = '-';
228
229			/*
230			 * Go to the end of the option argument.  Save off any
231			 * trailing options (-3lf) and translate any trailing
232			 * output style characters.
233			 */
234			t = *argv + len - 1;
235			if (*t == 'f' || *t == 'r') {
236				*p++ = *t;
237				*t-- = '\0';
238			}
239			switch(*t) {
240			case 'b':
241				*p++ = 'b';
242				*t = '\0';
243				break;
244			case 'c':
245				*p++ = 'c';
246				*t = '\0';
247				break;
248			case 'l':
249				*t = '\0';
250				/* FALLTHROUGH */
251			case '0': case '1': case '2': case '3': case '4':
252			case '5': case '6': case '7': case '8': case '9':
253				*p++ = 'n';
254				break;
255			default:
256				errx(1, "illegal option -- %s", *argv);
257			}
258			*p++ = *argv[0];
259			(void)strlcpy(p, ap, start + len + 4 - p);
260			*argv = start;
261			continue;
262
263		/*
264		 * Options w/ arguments, skip the argument and continue
265		 * with the next option.
266		 */
267		case 'b':
268		case 'c':
269		case 'n':
270			if (!ap[1])
271				++argv;
272			/* FALLTHROUGH */
273		/* Options w/o arguments, continue with the next option. */
274		case 'f':
275		case 'r':
276			continue;
277
278		/* Illegal option, return and let getopt handle it. */
279		default:
280			return;
281		}
282	}
283}
284
285static void
286usage(void)
287{
288	(void)fprintf(stderr,
289	    "usage: tail [-f | -r] "
290	    "[-b number | -c number | -n number | -number] [file ...]\n");
291	exit(1);
292}
293