1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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/cdefs.h>
36
37__FBSDID("$FreeBSD$");
38
39#ifndef lint
40static const char copyright[] =
41"@(#) Copyright (c) 1991, 1993\n\
42	The Regents of the University of California.  All rights reserved.\n";
43#endif
44
45#ifndef lint
46static const char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
47#endif
48
49#include <sys/types.h>
50#include <sys/stat.h>
51
52#include <err.h>
53#include <errno.h>
54#include <getopt.h>
55#include <stdio.h>
56#include <stdlib.h>
57#include <string.h>
58#include <unistd.h>
59
60#include "extern.h"
61
62int Fflag, fflag, qflag, rflag, rval, no_files;
63
64static file_info_t *files;
65
66static void obsolete(char **);
67static void usage(void);
68
69static const struct option long_opts[] =
70{
71	{"blocks",	required_argument,	NULL, 'b'},
72	{"bytes",	required_argument,	NULL, 'c'},
73	{"lines",	required_argument,	NULL, 'n'},
74	{NULL,		no_argument,		NULL, 0}
75};
76
77int
78main(int argc, char *argv[])
79{
80	struct stat sb;
81	const char *fn;
82	FILE *fp;
83	off_t off;
84	enum STYLE style;
85	int i, ch, first;
86	file_info_t *file;
87	char *p;
88
89	/*
90	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
91	 * -n+10.  Second, the number options are 1 based and not offsets,
92	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
93	 * number options for the -r option specify the number of things that
94	 * get displayed, not the starting point in the file.  The one major
95	 * incompatibility in this version as compared to historical versions
96	 * is that the 'r' option couldn't be modified by the -lbc options,
97	 * i.e. it was always done in lines.  This version treats -rc as a
98	 * number of characters in reverse order.  Finally, the default for
99	 * -r is the entire file, not 10 lines.
100	 */
101#define	ARG(units, forward, backward) {					\
102	if (style)							\
103		usage();						\
104	off = strtoll(optarg, &p, 10) * (units);                        \
105	if (*p)								\
106		errx(1, "illegal offset -- %s", optarg);		\
107	switch(optarg[0]) {						\
108	case '+':							\
109		if (off)						\
110			off -= (units);					\
111			style = (forward);				\
112		break;							\
113	case '-':							\
114		off = -off;						\
115		/* FALLTHROUGH */					\
116	default:							\
117		style = (backward);					\
118		break;							\
119	}								\
120}
121
122	obsolete(argv);
123	style = NOTSET;
124	off = 0;
125	while ((ch = getopt_long(argc, argv, "+Fb:c:fn:qr", long_opts, NULL)) !=
126	    -1)
127		switch(ch) {
128		case 'F':	/* -F is superset of (and implies) -f */
129			Fflag = fflag = 1;
130			break;
131		case 'b':
132			ARG(512, FBYTES, RBYTES);
133			break;
134		case 'c':
135			ARG(1, FBYTES, RBYTES);
136			break;
137		case 'f':
138			fflag = 1;
139			break;
140		case 'n':
141			ARG(1, FLINES, RLINES);
142			break;
143		case 'q':
144			qflag = 1;
145			break;
146		case 'r':
147			rflag = 1;
148			break;
149		case '?':
150		default:
151			usage();
152		}
153	argc -= optind;
154	argv += optind;
155
156	no_files = argc ? argc : 1;
157
158	/*
159	 * If displaying in reverse, don't permit follow option, and convert
160	 * style values.
161	 */
162	if (rflag) {
163		if (fflag)
164			usage();
165		if (style == FBYTES)
166			style = RBYTES;
167		else if (style == FLINES)
168			style = RLINES;
169	}
170
171	/*
172	 * If style not specified, the default is the whole file for -r, and
173	 * the last 10 lines if not -r.
174	 */
175	if (style == NOTSET) {
176		if (rflag) {
177			off = 0;
178			style = REVERSE;
179		} else {
180			off = 10;
181			style = RLINES;
182		}
183	}
184
185	if (*argv && fflag) {
186		files = (struct file_info *) malloc(no_files *
187		    sizeof(struct file_info));
188		if (!files)
189			err(1, "Couldn't malloc space for file descriptors.");
190
191		for (file = files; (fn = *argv++); file++) {
192			file->file_name = strdup(fn);
193			if (! file->file_name)
194				errx(1, "Couldn't malloc space for file name.");
195			if ((file->fp = fopen(file->file_name, "r")) == NULL ||
196			    fstat(fileno(file->fp), &file->st)) {
197				if (file->fp != NULL) {
198					fclose(file->fp);
199					file->fp = NULL;
200				}
201				if (!Fflag || errno != ENOENT)
202					ierr(file->file_name);
203			}
204		}
205		follow(files, style, off);
206		for (i = 0, file = files; i < no_files; i++, file++) {
207		    free(file->file_name);
208		}
209		free(files);
210	} else if (*argv) {
211		for (first = 1; (fn = *argv++);) {
212			if ((fp = fopen(fn, "r")) == NULL ||
213			    fstat(fileno(fp), &sb)) {
214				ierr(fn);
215				continue;
216			}
217			if (argc > 1 && !qflag) {
218				printfn(fn, !first);
219				first = 0;
220			}
221
222			if (rflag)
223				reverse(fp, fn, style, off, &sb);
224			else
225				forward(fp, fn, style, off, &sb);
226		}
227	} else {
228		fn = "stdin";
229
230		if (fstat(fileno(stdin), &sb)) {
231			ierr(fn);
232			exit(1);
233		}
234
235		/*
236		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
237		 * bit in the st_mode field for pipes.  Fix this then.
238		 */
239		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
240		    errno == ESPIPE) {
241			errno = 0;
242			fflag = 0;		/* POSIX.2 requires this. */
243		}
244
245		if (rflag)
246			reverse(stdin, fn, style, off, &sb);
247		else
248			forward(stdin, fn, style, off, &sb);
249	}
250	exit(rval);
251}
252
253/*
254 * Convert the obsolete argument form into something that getopt can handle.
255 * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
256 * the option argument for a -b, -c or -n option gets converted.
257 */
258static void
259obsolete(char *argv[])
260{
261	char *ap, *p, *t;
262	size_t len;
263	char *start;
264
265	while ((ap = *++argv)) {
266		/* Return if "--" or not an option of any form. */
267		if (ap[0] != '-') {
268			if (ap[0] != '+')
269				return;
270		} else if (ap[1] == '-')
271			return;
272
273		switch(*++ap) {
274		/* Old-style option. */
275		case '0': case '1': case '2': case '3': case '4':
276		case '5': case '6': case '7': case '8': case '9':
277
278			/* Malloc space for dash, new option and argument. */
279			len = strlen(*argv);
280			if ((start = p = malloc(len + 3)) == NULL)
281				err(1, "malloc");
282			*p++ = '-';
283
284			/*
285			 * Go to the end of the option argument.  Save off any
286			 * trailing options (-3lf) and translate any trailing
287			 * output style characters.
288			 */
289			t = *argv + len - 1;
290			if (*t == 'F' || *t == 'f' || *t == 'r') {
291				*p++ = *t;
292				*t-- = '\0';
293			}
294			switch(*t) {
295			case 'b':
296				*p++ = 'b';
297				*t = '\0';
298				break;
299			case 'c':
300				*p++ = 'c';
301				*t = '\0';
302				break;
303			case 'l':
304				*t = '\0';
305				/* FALLTHROUGH */
306			case '0': case '1': case '2': case '3': case '4':
307			case '5': case '6': case '7': case '8': case '9':
308				*p++ = 'n';
309				break;
310			default:
311				errx(1, "illegal option -- %s", *argv);
312			}
313			*p++ = *argv[0];
314			(void)strcpy(p, ap);
315			*argv = start;
316			continue;
317
318		/*
319		 * Options w/ arguments, skip the argument and continue
320		 * with the next option.
321		 */
322		case 'b':
323		case 'c':
324		case 'n':
325			if (!ap[1])
326				++argv;
327			/* FALLTHROUGH */
328		/* Options w/o arguments, continue with the next option. */
329		case 'F':
330		case 'f':
331		case 'r':
332			continue;
333
334		/* Illegal option, return and let getopt handle it. */
335		default:
336			return;
337		}
338	}
339}
340
341static void
342usage(void)
343{
344	(void)fprintf(stderr,
345	    "usage: tail [-F | -f | -r] [-q] [-b # | -c # | -n #]"
346	    " [file ...]\n");
347	exit(1);
348}
349