xref: /freebsd/usr.bin/tail/tail.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
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("$FreeBSD$");
40 
41 #ifndef lint
42 static 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
48 static 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 
63 int Fflag, fflag, qflag, rflag, rval, no_files;
64 const char *fname;
65 
66 file_info_t *files;
67 
68 static void obsolete(char **);
69 static void usage(void);
70 
71 int
72 main(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 	off = 0;
118 	while ((ch = getopt(argc, argv, "Fb:c:fn:qr")) != -1)
119 		switch(ch) {
120 		case 'F':	/* -F is superset of (and implies) -f */
121 			Fflag = fflag = 1;
122 			break;
123 		case 'b':
124 			ARG(512, FBYTES, RBYTES);
125 			break;
126 		case 'c':
127 			ARG(1, FBYTES, RBYTES);
128 			break;
129 		case 'f':
130 			fflag = 1;
131 			break;
132 		case 'n':
133 			ARG(1, FLINES, RLINES);
134 			break;
135 		case 'q':
136 			qflag = 1;
137 			break;
138 		case 'r':
139 			rflag = 1;
140 			break;
141 		case '?':
142 		default:
143 			usage();
144 		}
145 	argc -= optind;
146 	argv += optind;
147 
148 	no_files = argc ? argc : 1;
149 
150 	/*
151 	 * If displaying in reverse, don't permit follow option, and convert
152 	 * style values.
153 	 */
154 	if (rflag) {
155 		if (fflag)
156 			usage();
157 		if (style == FBYTES)
158 			style = RBYTES;
159 		else if (style == FLINES)
160 			style = RLINES;
161 	}
162 
163 	/*
164 	 * If style not specified, the default is the whole file for -r, and
165 	 * the last 10 lines if not -r.
166 	 */
167 	if (style == NOTSET) {
168 		if (rflag) {
169 			off = 0;
170 			style = REVERSE;
171 		} else {
172 			off = 10;
173 			style = RLINES;
174 		}
175 	}
176 
177 	if (*argv && fflag) {
178 		files = (struct file_info *) malloc(no_files * sizeof(struct file_info));
179 		if (! files)
180 			err(1, "Couldn't malloc space for file descriptors.");
181 
182 		for (file = files; (fname = *argv++); file++) {
183 			file->file_name = malloc(strlen(fname)+1);
184 			if (! file->file_name)
185 				errx(1, "Couldn't malloc space for file name.");
186 			strncpy(file->file_name, fname, strlen(fname)+1);
187 			if ((file->fp = fopen(file->file_name, "r")) == NULL ||
188 			    fstat(fileno(file->fp), &file->st)) {
189 				file->fp = NULL;
190 				ierr();
191 				continue;
192 			}
193 		}
194 		follow(files, style, off);
195 		for (i = 0, file = files; i < no_files; i++, file++) {
196 		    free(file->file_name);
197 		}
198 		free(files);
199 	} else if (*argv) {
200 		for (first = 1; (fname = *argv++);) {
201 			if ((fp = fopen(fname, "r")) == NULL ||
202 			    fstat(fileno(fp), &sb)) {
203 				ierr();
204 				continue;
205 			}
206 			if (argc > 1 && !qflag) {
207 				(void)printf("%s==> %s <==\n",
208 				    first ? "" : "\n", fname);
209 				first = 0;
210 				(void)fflush(stdout);
211 			}
212 
213 			if (rflag)
214 				reverse(fp, style, off, &sb);
215 			else
216 				forward(fp, style, off, &sb);
217 		}
218 	} else {
219 		fname = "stdin";
220 
221 		if (fstat(fileno(stdin), &sb)) {
222 			ierr();
223 			exit(1);
224 		}
225 
226 		/*
227 		 * Determine if input is a pipe.  4.4BSD will set the SOCKET
228 		 * bit in the st_mode field for pipes.  Fix this then.
229 		 */
230 		if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
231 		    errno == ESPIPE) {
232 			errno = 0;
233 			fflag = 0;		/* POSIX.2 requires this. */
234 		}
235 
236 		if (rflag)
237 			reverse(stdin, style, off, &sb);
238 		else
239 			forward(stdin, style, off, &sb);
240 	}
241 	exit(rval);
242 }
243 
244 /*
245  * Convert the obsolete argument form into something that getopt can handle.
246  * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
247  * the option argument for a -b, -c or -n option gets converted.
248  */
249 static void
250 obsolete(char *argv[])
251 {
252 	char *ap, *p, *t;
253 	size_t len;
254 	char *start;
255 
256 	while ((ap = *++argv)) {
257 		/* Return if "--" or not an option of any form. */
258 		if (ap[0] != '-') {
259 			if (ap[0] != '+')
260 				return;
261 		} else if (ap[1] == '-')
262 			return;
263 
264 		switch(*++ap) {
265 		/* Old-style option. */
266 		case '0': case '1': case '2': case '3': case '4':
267 		case '5': case '6': case '7': case '8': case '9':
268 
269 			/* Malloc space for dash, new option and argument. */
270 			len = strlen(*argv);
271 			if ((start = p = malloc(len + 3)) == NULL)
272 				err(1, "malloc");
273 			*p++ = '-';
274 
275 			/*
276 			 * Go to the end of the option argument.  Save off any
277 			 * trailing options (-3lf) and translate any trailing
278 			 * output style characters.
279 			 */
280 			t = *argv + len - 1;
281 			if (*t == 'F' || *t == 'f' || *t == 'r') {
282 				*p++ = *t;
283 				*t-- = '\0';
284 			}
285 			switch(*t) {
286 			case 'b':
287 				*p++ = 'b';
288 				*t = '\0';
289 				break;
290 			case 'c':
291 				*p++ = 'c';
292 				*t = '\0';
293 				break;
294 			case 'l':
295 				*t = '\0';
296 				/* FALLTHROUGH */
297 			case '0': case '1': case '2': case '3': case '4':
298 			case '5': case '6': case '7': case '8': case '9':
299 				*p++ = 'n';
300 				break;
301 			default:
302 				errx(1, "illegal option -- %s", *argv);
303 			}
304 			*p++ = *argv[0];
305 			(void)strcpy(p, ap);
306 			*argv = start;
307 			continue;
308 
309 		/*
310 		 * Options w/ arguments, skip the argument and continue
311 		 * with the next option.
312 		 */
313 		case 'b':
314 		case 'c':
315 		case 'n':
316 			if (!ap[1])
317 				++argv;
318 			/* FALLTHROUGH */
319 		/* Options w/o arguments, continue with the next option. */
320 		case 'F':
321 		case 'f':
322 		case 'r':
323 			continue;
324 
325 		/* Illegal option, return and let getopt handle it. */
326 		default:
327 			return;
328 		}
329 	}
330 }
331 
332 static void
333 usage(void)
334 {
335 	(void)fprintf(stderr,
336 	    "usage: tail [-F | -f | -r] [-q] [-b # | -c # | -n #]"
337 	    " [file ...]\n");
338 	exit(1);
339 }
340