tail.c revision 137157 
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. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#include <sys/cdefs.h>
38
39__FBSDID("$FreeBSD: head/usr.bin/tail/tail.c 137157 2004-11-03 15:23:11Z paul $");
40
41#ifndef lint
42static const char copyright[] =
43"@(#) Copyright (c) 1991, 1993\n\
44	The Regents of the University of California.  All rights reserved.\n";
45#endif
46
47#ifndef lint
48static const char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
49#endif
50
51#include <sys/types.h>
52#include <sys/stat.h>
53
54#include <err.h>
55#include <errno.h>
56#include <stdio.h>
57#include <stdlib.h>
58#include <string.h>
59#include <unistd.h>
60
61#include "extern.h"
62
63int Fflag, fflag, rflag, rval;
64const char *fname;
65
66int no_files;
67
68static void obsolete(char **);
69static void usage(void);
70
71int
72main(int argc, char *argv[])
73{
74	struct stat sb;
75	FILE *fp;
76	off_t off;
77	enum STYLE style;
78	int ch, first;
79	char *p;
80
81	/*
82	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
83	 * -n+10.  Second, the number options are 1 based and not offsets,
84	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
85	 * number options for the -r option specify the number of things that
86	 * get displayed, not the starting point in the file.  The one major
87	 * incompatibility in this version as compared to historical versions
88	 * is that the 'r' option couldn't be modified by the -lbc options,
89	 * i.e. it was always done in lines.  This version treats -rc as a
90	 * number of characters in reverse order.  Finally, the default for
91	 * -r is the entire file, not 10 lines.
92	 */
93#define	ARG(units, forward, backward) {					\
94	if (style)							\
95		usage();						\
96	off = strtoll(optarg, &p, 10) * (units);                        \
97	if (*p)								\
98		errx(1, "illegal offset -- %s", optarg);		\
99	switch(optarg[0]) {						\
100	case '+':							\
101		if (off)						\
102			off -= (units);					\
103			style = (forward);				\
104		break;							\
105	case '-':							\
106		off = -off;						\
107		/* FALLTHROUGH */					\
108	default:							\
109		style = (backward);					\
110		break;							\
111	}								\
112}
113
114	obsolete(argv);
115	style = NOTSET;
116	while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -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 'r':
134			rflag = 1;
135			break;
136		case '?':
137		default:
138			usage();
139		}
140	argc -= optind;
141	argv += optind;
142
143	no_files = argc;
144
145	/*
146	 * If displaying in reverse, don't permit follow option, and convert
147	 * style values.
148	 */
149	if (rflag) {
150		if (fflag)
151			usage();
152		if (style == FBYTES)
153			style = RBYTES;
154		else if (style == FLINES)
155			style = RLINES;
156	}
157
158	/*
159	 * If style not specified, the default is the whole file for -r, and
160	 * the last 10 lines if not -r.
161	 */
162	if (style == NOTSET) {
163		if (rflag) {
164			off = 0;
165			style = REVERSE;
166		} else {
167			off = 10;
168			style = RLINES;
169		}
170	}
171
172	printf("No files: %d\n", no_files);
173	if (*argv)
174		for (first = 1; (fname = *argv++);) {
175			if ((fp = fopen(fname, "r")) == NULL ||
176			    fstat(fileno(fp), &sb)) {
177				ierr();
178				continue;
179			}
180			if (argc > 1) {
181				(void)printf("%s==> %s <==\n",
182				    first ? "" : "\n", fname);
183				first = 0;
184				(void)fflush(stdout);
185			}
186
187			if (rflag)
188				reverse(fp, style, off, &sb);
189			else
190				forward(fp, style, off, &sb);
191			(void)fclose(fp);
192		}
193	else {
194		fname = "stdin";
195
196		if (fstat(fileno(stdin), &sb)) {
197			ierr();
198			exit(1);
199		}
200
201		/*
202		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
203		 * bit in the st_mode field for pipes.  Fix this then.
204		 */
205		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
206		    errno == ESPIPE) {
207			errno = 0;
208			fflag = 0;		/* POSIX.2 requires this. */
209		}
210
211		if (rflag)
212			reverse(stdin, style, off, &sb);
213		else
214			forward(stdin, style, off, &sb);
215	}
216	exit(rval);
217}
218
219/*
220 * Convert the obsolete argument form into something that getopt can handle.
221 * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
222 * the option argument for a -b, -c or -n option gets converted.
223 */
224static void
225obsolete(char *argv[])
226{
227	char *ap, *p, *t;
228	size_t len;
229	char *start;
230
231	while ((ap = *++argv)) {
232		/* Return if "--" or not an option of any form. */
233		if (ap[0] != '-') {
234			if (ap[0] != '+')
235				return;
236		} else if (ap[1] == '-')
237			return;
238
239		switch(*++ap) {
240		/* Old-style option. */
241		case '0': case '1': case '2': case '3': case '4':
242		case '5': case '6': case '7': case '8': case '9':
243
244			/* Malloc space for dash, new option and argument. */
245			len = strlen(*argv);
246			if ((start = p = malloc(len + 3)) == NULL)
247				err(1, "malloc");
248			*p++ = '-';
249
250			/*
251			 * Go to the end of the option argument.  Save off any
252			 * trailing options (-3lf) and translate any trailing
253			 * output style characters.
254			 */
255			t = *argv + len - 1;
256			if (*t == 'F' || *t == 'f' || *t == 'r') {
257				*p++ = *t;
258				*t-- = '\0';
259			}
260			switch(*t) {
261			case 'b':
262				*p++ = 'b';
263				*t = '\0';
264				break;
265			case 'c':
266				*p++ = 'c';
267				*t = '\0';
268				break;
269			case 'l':
270				*t = '\0';
271				/* FALLTHROUGH */
272			case '0': case '1': case '2': case '3': case '4':
273			case '5': case '6': case '7': case '8': case '9':
274				*p++ = 'n';
275				break;
276			default:
277				errx(1, "illegal option -- %s", *argv);
278			}
279			*p++ = *argv[0];
280			(void)strcpy(p, ap);
281			*argv = start;
282			continue;
283
284		/*
285		 * Options w/ arguments, skip the argument and continue
286		 * with the next option.
287		 */
288		case 'b':
289		case 'c':
290		case 'n':
291			if (!ap[1])
292				++argv;
293			/* FALLTHROUGH */
294		/* Options w/o arguments, continue with the next option. */
295		case 'F':
296		case 'f':
297		case 'r':
298			continue;
299
300		/* Illegal option, return and let getopt handle it. */
301		default:
302			return;
303		}
304	}
305}
306
307static void
308usage(void)
309{
310	(void)fprintf(stderr,
311	    "usage: tail [-F | -f | -r] [-b # | -c # | -n #] [file ...]\n");
312	exit(1);
313}
314