tail.c revision 99983 
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 99983 2002-07-14 18:21:07Z alfred $");
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
66static void obsolete(char **);
67static void usage(void);
68
69int
70main(int argc, char *argv[])
71{
72	struct stat sb;
73	FILE *fp;
74	off_t off;
75	enum STYLE style;
76	int ch, first;
77	char *p;
78
79	/*
80	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
81	 * -n+10.  Second, the number options are 1 based and not offsets,
82	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
83	 * number options for the -r option specify the number of things that
84	 * get displayed, not the starting point in the file.  The one major
85	 * incompatibility in this version as compared to historical versions
86	 * is that the 'r' option couldn't be modified by the -lbc options,
87	 * i.e. it was always done in lines.  This version treats -rc as a
88	 * number of characters in reverse order.  Finally, the default for
89	 * -r is the entire file, not 10 lines.
90	 */
91#define	ARG(units, forward, backward) {					\
92	if (style)							\
93		usage();						\
94	off = strtoll(optarg, &p, 10) * (units);                        \
95	if (*p)								\
96		errx(1, "illegal offset -- %s", optarg);		\
97	switch(optarg[0]) {						\
98	case '+':							\
99		if (off)						\
100			off -= (units);					\
101			style = (forward);				\
102		break;							\
103	case '-':							\
104		off = -off;						\
105		/* FALLTHROUGH */					\
106	default:							\
107		style = (backward);					\
108		break;							\
109	}								\
110}
111
112	obsolete(argv);
113	style = NOTSET;
114	while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1)
115		switch(ch) {
116		case 'F':	/* -F is superset of (and implies) -f */
117			Fflag = fflag = 1;
118			break;
119		case 'b':
120			ARG(512, FBYTES, RBYTES);
121			break;
122		case 'c':
123			ARG(1, FBYTES, RBYTES);
124			break;
125		case 'f':
126			fflag = 1;
127			break;
128		case 'n':
129			ARG(1, FLINES, RLINES);
130			break;
131		case 'r':
132			rflag = 1;
133			break;
134		case '?':
135		default:
136			usage();
137		}
138	argc -= optind;
139	argv += optind;
140
141	if (fflag && argc > 1)
142		errx(1, "-f option only appropriate for a single file");
143
144	/*
145	 * If displaying in reverse, don't permit follow option, and convert
146	 * style values.
147	 */
148	if (rflag) {
149		if (fflag)
150			usage();
151		if (style == FBYTES)
152			style = RBYTES;
153		else if (style == FLINES)
154			style = RLINES;
155	}
156
157	/*
158	 * If style not specified, the default is the whole file for -r, and
159	 * the last 10 lines if not -r.
160	 */
161	if (style == NOTSET) {
162		if (rflag) {
163			off = 0;
164			style = REVERSE;
165		} else {
166			off = 10;
167			style = RLINES;
168		}
169	}
170
171	if (*argv)
172		for (first = 1; (fname = *argv++);) {
173			if ((fp = fopen(fname, "r")) == NULL ||
174			    fstat(fileno(fp), &sb)) {
175				ierr();
176				continue;
177			}
178			if (argc > 1) {
179				(void)printf("%s==> %s <==\n",
180				    first ? "" : "\n", fname);
181				first = 0;
182				(void)fflush(stdout);
183			}
184
185			if (rflag)
186				reverse(fp, style, off, &sb);
187			else
188				forward(fp, style, off, &sb);
189			(void)fclose(fp);
190		}
191	else {
192		fname = "stdin";
193
194		if (fstat(fileno(stdin), &sb)) {
195			ierr();
196			exit(1);
197		}
198
199		/*
200		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
201		 * bit in the st_mode field for pipes.  Fix this then.
202		 */
203		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
204		    errno == ESPIPE) {
205			errno = 0;
206			fflag = 0;		/* POSIX.2 requires this. */
207		}
208
209		if (rflag)
210			reverse(stdin, style, off, &sb);
211		else
212			forward(stdin, style, off, &sb);
213	}
214	exit(rval);
215}
216
217/*
218 * Convert the obsolete argument form into something that getopt can handle.
219 * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
220 * the option argument for a -b, -c or -n option gets converted.
221 */
222static void
223obsolete(char *argv[])
224{
225	char *ap, *p, *t;
226	size_t len;
227	char *start;
228
229	while ((ap = *++argv)) {
230		/* Return if "--" or not an option of any form. */
231		if (ap[0] != '-') {
232			if (ap[0] != '+')
233				return;
234		} else if (ap[1] == '-')
235			return;
236
237		switch(*++ap) {
238		/* Old-style option. */
239		case '0': case '1': case '2': case '3': case '4':
240		case '5': case '6': case '7': case '8': case '9':
241
242			/* Malloc space for dash, new option and argument. */
243			len = strlen(*argv);
244			if ((start = p = malloc(len + 3)) == NULL)
245				err(1, "malloc");
246			*p++ = '-';
247
248			/*
249			 * Go to the end of the option argument.  Save off any
250			 * trailing options (-3lf) and translate any trailing
251			 * output style characters.
252			 */
253			t = *argv + len - 1;
254			if (*t == 'F' || *t == 'f' || *t == 'r') {
255				*p++ = *t;
256				*t-- = '\0';
257			}
258			switch(*t) {
259			case 'b':
260				*p++ = 'b';
261				*t = '\0';
262				break;
263			case 'c':
264				*p++ = 'c';
265				*t = '\0';
266				break;
267			case 'l':
268				*t = '\0';
269				/* FALLTHROUGH */
270			case '0': case '1': case '2': case '3': case '4':
271			case '5': case '6': case '7': case '8': case '9':
272				*p++ = 'n';
273				break;
274			default:
275				errx(1, "illegal option -- %s", *argv);
276			}
277			*p++ = *argv[0];
278			(void)strcpy(p, ap);
279			*argv = start;
280			continue;
281
282		/*
283		 * Options w/ arguments, skip the argument and continue
284		 * with the next option.
285		 */
286		case 'b':
287		case 'c':
288		case 'n':
289			if (!ap[1])
290				++argv;
291			/* FALLTHROUGH */
292		/* Options w/o arguments, continue with the next option. */
293		case 'F':
294		case 'f':
295		case 'r':
296			continue;
297
298		/* Illegal option, return and let getopt handle it. */
299		default:
300			return;
301		}
302	}
303}
304
305static void
306usage(void)
307{
308	(void)fprintf(stderr,
309	    "usage: tail [-F | -f | -r] [-b # | -c # | -n #] [file ...]\n");
310	exit(1);
311}
312