tail.c revision 137225 
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 137225 2004-11-04 19:18:19Z 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, no_files;
64const char *fname;
65
66file_info_t *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 i, ch, first;
79	file_info_t *file;
80	char *p;
81
82	/*
83	 * Tail's options are weird.  First, -n10 is the same as -n-10, not
84	 * -n+10.  Second, the number options are 1 based and not offsets,
85	 * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
86	 * number options for the -r option specify the number of things that
87	 * get displayed, not the starting point in the file.  The one major
88	 * incompatibility in this version as compared to historical versions
89	 * is that the 'r' option couldn't be modified by the -lbc options,
90	 * i.e. it was always done in lines.  This version treats -rc as a
91	 * number of characters in reverse order.  Finally, the default for
92	 * -r is the entire file, not 10 lines.
93	 */
94#define	ARG(units, forward, backward) {					\
95	if (style)							\
96		usage();						\
97	off = strtoll(optarg, &p, 10) * (units);                        \
98	if (*p)								\
99		errx(1, "illegal offset -- %s", optarg);		\
100	switch(optarg[0]) {						\
101	case '+':							\
102		if (off)						\
103			off -= (units);					\
104			style = (forward);				\
105		break;							\
106	case '-':							\
107		off = -off;						\
108		/* FALLTHROUGH */					\
109	default:							\
110		style = (backward);					\
111		break;							\
112	}								\
113}
114
115	obsolete(argv);
116	style = NOTSET;
117	while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1)
118		switch(ch) {
119		case 'F':	/* -F is superset of (and implies) -f */
120			Fflag = fflag = 1;
121			break;
122		case 'b':
123			ARG(512, FBYTES, RBYTES);
124			break;
125		case 'c':
126			ARG(1, FBYTES, RBYTES);
127			break;
128		case 'f':
129			fflag = 1;
130			break;
131		case 'n':
132			ARG(1, FLINES, RLINES);
133			break;
134		case 'r':
135			rflag = 1;
136			break;
137		case '?':
138		default:
139			usage();
140		}
141	argc -= optind;
142	argv += optind;
143
144	no_files = argc ? argc : 1;
145
146	/*
147	 * If displaying in reverse, don't permit follow option, and convert
148	 * style values.
149	 */
150	if (rflag) {
151		if (fflag)
152			usage();
153		if (style == FBYTES)
154			style = RBYTES;
155		else if (style == FLINES)
156			style = RLINES;
157	}
158
159	/*
160	 * If style not specified, the default is the whole file for -r, and
161	 * the last 10 lines if not -r.
162	 */
163	if (style == NOTSET) {
164		if (rflag) {
165			off = 0;
166			style = REVERSE;
167		} else {
168			off = 10;
169			style = RLINES;
170		}
171	}
172
173	if (*argv && fflag) {
174		files = (struct file_info *) malloc(no_files * sizeof(struct file_info));
175		if (! files)
176			err(1, "Couldn't malloc space for file descriptors.");
177
178		for (file = files; (fname = *argv++); file++) {
179			file->file_name = malloc(strlen(fname)+1);
180			if (! file->file_name)
181				errx(1, "Couldn't malloc space for file name.");
182			strncpy(file->file_name, fname, strlen(fname)+1);
183			if ((file->fp = fopen(file->file_name, "r")) == NULL ||
184			    fstat(fileno(file->fp), &file->st)) {
185				file->fp = NULL;
186				ierr();
187				continue;
188			}
189		}
190		follow(files, style, off);
191		for (i = 0, file = files; i < no_files; i++, file++) {
192		    free(file->file_name);
193		}
194		free(files);
195	} else if (*argv) {
196		for (first = 1; (fname = *argv++);) {
197			if ((fp = fopen(fname, "r")) == NULL ||
198			    fstat(fileno(fp), &sb)) {
199				ierr();
200				continue;
201			}
202			if (argc > 1) {
203				(void)printf("%s==> %s <==\n",
204				    first ? "" : "\n", fname);
205				first = 0;
206				(void)fflush(stdout);
207			}
208
209			if (rflag)
210				reverse(fp, style, off, &sb);
211			else
212				forward(fp, style, off, &sb);
213		}
214	} else {
215		fname = "stdin";
216
217		if (fstat(fileno(stdin), &sb)) {
218			ierr();
219			exit(1);
220		}
221
222		/*
223		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
224		 * bit in the st_mode field for pipes.  Fix this then.
225		 */
226		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
227		    errno == ESPIPE) {
228			errno = 0;
229			fflag = 0;		/* POSIX.2 requires this. */
230		}
231
232		if (rflag)
233			reverse(stdin, style, off, &sb);
234		else
235			forward(stdin, style, off, &sb);
236	}
237	exit(rval);
238}
239
240/*
241 * Convert the obsolete argument form into something that getopt can handle.
242 * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
243 * the option argument for a -b, -c or -n option gets converted.
244 */
245static void
246obsolete(char *argv[])
247{
248	char *ap, *p, *t;
249	size_t len;
250	char *start;
251
252	while ((ap = *++argv)) {
253		/* Return if "--" or not an option of any form. */
254		if (ap[0] != '-') {
255			if (ap[0] != '+')
256				return;
257		} else if (ap[1] == '-')
258			return;
259
260		switch(*++ap) {
261		/* Old-style option. */
262		case '0': case '1': case '2': case '3': case '4':
263		case '5': case '6': case '7': case '8': case '9':
264
265			/* Malloc space for dash, new option and argument. */
266			len = strlen(*argv);
267			if ((start = p = malloc(len + 3)) == NULL)
268				err(1, "malloc");
269			*p++ = '-';
270
271			/*
272			 * Go to the end of the option argument.  Save off any
273			 * trailing options (-3lf) and translate any trailing
274			 * output style characters.
275			 */
276			t = *argv + len - 1;
277			if (*t == 'F' || *t == 'f' || *t == 'r') {
278				*p++ = *t;
279				*t-- = '\0';
280			}
281			switch(*t) {
282			case 'b':
283				*p++ = 'b';
284				*t = '\0';
285				break;
286			case 'c':
287				*p++ = 'c';
288				*t = '\0';
289				break;
290			case 'l':
291				*t = '\0';
292				/* FALLTHROUGH */
293			case '0': case '1': case '2': case '3': case '4':
294			case '5': case '6': case '7': case '8': case '9':
295				*p++ = 'n';
296				break;
297			default:
298				errx(1, "illegal option -- %s", *argv);
299			}
300			*p++ = *argv[0];
301			(void)strcpy(p, ap);
302			*argv = start;
303			continue;
304
305		/*
306		 * Options w/ arguments, skip the argument and continue
307		 * with the next option.
308		 */
309		case 'b':
310		case 'c':
311		case 'n':
312			if (!ap[1])
313				++argv;
314			/* FALLTHROUGH */
315		/* Options w/o arguments, continue with the next option. */
316		case 'F':
317		case 'f':
318		case 'r':
319			continue;
320
321		/* Illegal option, return and let getopt handle it. */
322		default:
323			return;
324		}
325	}
326}
327
328static void
329usage(void)
330{
331	(void)fprintf(stderr,
332	    "usage: tail [-F | -f | -r] [-b # | -c # | -n #] [file ...]\n");
333	exit(1);
334}
335