tail.c revision 330897 
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 * 4. 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: stable/11/usr.bin/tail/tail.c 330897 2018-03-14 03:19:51Z eadler $");
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 <stdio.h>
55#include <stdlib.h>
56#include <string.h>
57#include <unistd.h>
58
59#include "extern.h"
60
61int Fflag, fflag, qflag, rflag, rval, no_files;
62
63static file_info_t *files;
64
65static void obsolete(char **);
66static void usage(void);
67
68int
69main(int argc, char *argv[])
70{
71	struct stat sb;
72	const char *fn;
73	FILE *fp;
74	off_t off;
75	enum STYLE style;
76	int i, ch, first;
77	file_info_t *file;
78	char *p;
79
80	/*
81	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
82	 * -n+10.  Second, the number options are 1 based and not offsets,
83	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
84	 * number options for the -r option specify the number of things that
85	 * get displayed, not the starting point in the file.  The one major
86	 * incompatibility in this version as compared to historical versions
87	 * is that the 'r' option couldn't be modified by the -lbc options,
88	 * i.e. it was always done in lines.  This version treats -rc as a
89	 * number of characters in reverse order.  Finally, the default for
90	 * -r is the entire file, not 10 lines.
91	 */
92#define	ARG(units, forward, backward) {					\
93	if (style)							\
94		usage();						\
95	off = strtoll(optarg, &p, 10) * (units);                        \
96	if (*p)								\
97		errx(1, "illegal offset -- %s", optarg);		\
98	switch(optarg[0]) {						\
99	case '+':							\
100		if (off)						\
101			off -= (units);					\
102			style = (forward);				\
103		break;							\
104	case '-':							\
105		off = -off;						\
106		/* FALLTHROUGH */					\
107	default:							\
108		style = (backward);					\
109		break;							\
110	}								\
111}
112
113	obsolete(argv);
114	style = NOTSET;
115	off = 0;
116	while ((ch = getopt(argc, argv, "Fb:c:fn:qr")) != -1)
117		switch(ch) {
118		case 'F':	/* -F is superset of (and implies) -f */
119			Fflag = fflag = 1;
120			break;
121		case 'b':
122			ARG(512, FBYTES, RBYTES);
123			break;
124		case 'c':
125			ARG(1, FBYTES, RBYTES);
126			break;
127		case 'f':
128			fflag = 1;
129			break;
130		case 'n':
131			ARG(1, FLINES, RLINES);
132			break;
133		case 'q':
134			qflag = 1;
135			break;
136		case 'r':
137			rflag = 1;
138			break;
139		case '?':
140		default:
141			usage();
142		}
143	argc -= optind;
144	argv += optind;
145
146	no_files = argc ? argc : 1;
147
148	/*
149	 * If displaying in reverse, don't permit follow option, and convert
150	 * style values.
151	 */
152	if (rflag) {
153		if (fflag)
154			usage();
155		if (style == FBYTES)
156			style = RBYTES;
157		else if (style == FLINES)
158			style = RLINES;
159	}
160
161	/*
162	 * If style not specified, the default is the whole file for -r, and
163	 * the last 10 lines if not -r.
164	 */
165	if (style == NOTSET) {
166		if (rflag) {
167			off = 0;
168			style = REVERSE;
169		} else {
170			off = 10;
171			style = RLINES;
172		}
173	}
174
175	if (*argv && fflag) {
176		files = (struct file_info *) malloc(no_files *
177		    sizeof(struct file_info));
178		if (!files)
179			err(1, "Couldn't malloc space for file descriptors.");
180
181		for (file = files; (fn = *argv++); file++) {
182			file->file_name = strdup(fn);
183			if (! file->file_name)
184				errx(1, "Couldn't malloc space for file name.");
185			if ((file->fp = fopen(file->file_name, "r")) == NULL ||
186			    fstat(fileno(file->fp), &file->st)) {
187				if (file->fp != NULL) {
188					fclose(file->fp);
189					file->fp = NULL;
190				}
191				if (!Fflag || errno != ENOENT)
192					ierr(file->file_name);
193			}
194		}
195		follow(files, style, off);
196		for (i = 0, file = files; i < no_files; i++, file++) {
197		    free(file->file_name);
198		}
199		free(files);
200	} else if (*argv) {
201		for (first = 1; (fn = *argv++);) {
202			if ((fp = fopen(fn, "r")) == NULL ||
203			    fstat(fileno(fp), &sb)) {
204				ierr(fn);
205				continue;
206			}
207			if (argc > 1 && !qflag) {
208				printfn(fn, !first);
209				first = 0;
210			}
211
212			if (rflag)
213				reverse(fp, fn, style, off, &sb);
214			else
215				forward(fp, fn, style, off, &sb);
216		}
217	} else {
218		fn = "stdin";
219
220		if (fstat(fileno(stdin), &sb)) {
221			ierr(fn);
222			exit(1);
223		}
224
225		/*
226		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
227		 * bit in the st_mode field for pipes.  Fix this then.
228		 */
229		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
230		    errno == ESPIPE) {
231			errno = 0;
232			fflag = 0;		/* POSIX.2 requires this. */
233		}
234
235		if (rflag)
236			reverse(stdin, fn, style, off, &sb);
237		else
238			forward(stdin, fn, style, off, &sb);
239	}
240	exit(rval);
241}
242
243/*
244 * Convert the obsolete argument form into something that getopt can handle.
245 * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
246 * the option argument for a -b, -c or -n option gets converted.
247 */
248static void
249obsolete(char *argv[])
250{
251	char *ap, *p, *t;
252	size_t len;
253	char *start;
254
255	while ((ap = *++argv)) {
256		/* Return if "--" or not an option of any form. */
257		if (ap[0] != '-') {
258			if (ap[0] != '+')
259				return;
260		} else if (ap[1] == '-')
261			return;
262
263		switch(*++ap) {
264		/* Old-style option. */
265		case '0': case '1': case '2': case '3': case '4':
266		case '5': case '6': case '7': case '8': case '9':
267
268			/* Malloc space for dash, new option and argument. */
269			len = strlen(*argv);
270			if ((start = p = malloc(len + 3)) == NULL)
271				err(1, "malloc");
272			*p++ = '-';
273
274			/*
275			 * Go to the end of the option argument.  Save off any
276			 * trailing options (-3lf) and translate any trailing
277			 * output style characters.
278			 */
279			t = *argv + len - 1;
280			if (*t == 'F' || *t == 'f' || *t == 'r') {
281				*p++ = *t;
282				*t-- = '\0';
283			}
284			switch(*t) {
285			case 'b':
286				*p++ = 'b';
287				*t = '\0';
288				break;
289			case 'c':
290				*p++ = 'c';
291				*t = '\0';
292				break;
293			case 'l':
294				*t = '\0';
295				/* FALLTHROUGH */
296			case '0': case '1': case '2': case '3': case '4':
297			case '5': case '6': case '7': case '8': case '9':
298				*p++ = 'n';
299				break;
300			default:
301				errx(1, "illegal option -- %s", *argv);
302			}
303			*p++ = *argv[0];
304			(void)strcpy(p, ap);
305			*argv = start;
306			continue;
307
308		/*
309		 * Options w/ arguments, skip the argument and continue
310		 * with the next option.
311		 */
312		case 'b':
313		case 'c':
314		case 'n':
315			if (!ap[1])
316				++argv;
317			/* FALLTHROUGH */
318		/* Options w/o arguments, continue with the next option. */
319		case 'F':
320		case 'f':
321		case 'r':
322			continue;
323
324		/* Illegal option, return and let getopt handle it. */
325		default:
326			return;
327		}
328	}
329}
330
331static void
332usage(void)
333{
334	(void)fprintf(stderr,
335	    "usage: tail [-F | -f | -r] [-q] [-b # | -c # | -n #]"
336	    " [file ...]\n");
337	exit(1);
338}
339