1 /* $OpenBSD: tail.c,v 1.24 2022/12/04 23:50:49 cheloha Exp $ */
2
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 * 3. 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/types.h>
36 #include <sys/stat.h>
37
38 #include <err.h>
39 #include <errno.h>
40 #include <stdio.h>
41 #include <stdlib.h>
42 #include <string.h>
43 #include <unistd.h>
44
45 #include "extern.h"
46
47 int fflag, rflag, rval;
48
49 static void obsolete(char **);
50 static void usage(void);
51
52 int
main(int argc,char * argv[])53 main(int argc, char *argv[])
54 {
55 struct tailfile *tf;
56 off_t off = 0;
57 enum STYLE style;
58 int ch;
59 int i;
60 char *p;
61
62 if (pledge("stdio rpath", NULL) == -1)
63 err(1, "pledge");
64
65 /*
66 * Tail's options are weird. First, -n10 is the same as -n-10, not
67 * -n+10. Second, the number options are 1 based and not offsets,
68 * so -n+1 is the first line, and -c-1 is the last byte. Third, the
69 * number options for the -r option specify the number of things that
70 * get displayed, not the starting point in the file. The one major
71 * incompatibility in this version as compared to historical versions
72 * is that the 'r' option couldn't be modified by the -lbc options,
73 * i.e. it was always done in lines. This version treats -rc as a
74 * number of characters in reverse order. Finally, the default for
75 * -r is the entire file, not 10 lines.
76 */
77 #define ARG(units, forward, backward) { \
78 if (style) \
79 usage(); \
80 off = strtoll(optarg, &p, 10) * (units); \
81 if (*p) \
82 errx(1, "illegal offset -- %s", optarg); \
83 switch(optarg[0]) { \
84 case '+': \
85 if (off) \
86 off -= (units); \
87 style = (forward); \
88 break; \
89 case '-': \
90 off = -off; \
91 /* FALLTHROUGH */ \
92 default: \
93 style = (backward); \
94 break; \
95 } \
96 }
97
98 obsolete(argv);
99 style = NOTSET;
100 while ((ch = getopt(argc, argv, "b:c:fn:r")) != -1)
101 switch(ch) {
102 case 'b':
103 ARG(512, FBYTES, RBYTES);
104 break;
105 case 'c':
106 ARG(1, FBYTES, RBYTES);
107 break;
108 case 'f':
109 fflag = 1;
110 break;
111 case 'n':
112 ARG(1, FLINES, RLINES);
113 break;
114 case 'r':
115 rflag = 1;
116 break;
117 default:
118 usage();
119 }
120 argc -= optind;
121 argv += optind;
122
123 /*
124 * If displaying in reverse, don't permit follow option, and convert
125 * style values.
126 */
127 if (rflag) {
128 if (fflag)
129 usage();
130 if (style == FBYTES)
131 style = RBYTES;
132 else if (style == FLINES)
133 style = RLINES;
134 }
135
136 /*
137 * If style not specified, the default is the whole file for -r, and
138 * the last 10 lines if not -r.
139 */
140 if (style == NOTSET) {
141 if (rflag) {
142 off = 0;
143 style = REVERSE;
144 } else {
145 off = 10;
146 style = RLINES;
147 }
148 }
149
150 if ((tf = reallocarray(NULL, argc ? argc : 1, sizeof(*tf))) == NULL)
151 err(1, "reallocarray");
152
153 if (argc) {
154 for (i = 0; *argv; i++) {
155 tf[i].fname = *argv++;
156 if ((tf[i].fp = fopen(tf[i].fname, "r")) == NULL ||
157 fstat(fileno(tf[i].fp), &(tf[i].sb))) {
158 ierr(tf[i].fname);
159 i--;
160 continue;
161 }
162 }
163 if (rflag)
164 reverse(tf, i, style, off);
165 else
166 forward(tf, i, style, off);
167 }
168 else {
169 if (pledge("stdio", NULL) == -1)
170 err(1, "pledge");
171
172 tf[0].fname = "stdin";
173 tf[0].fp = stdin;
174
175 if (fstat(fileno(stdin), &(tf[0].sb))) {
176 ierr(tf[0].fname);
177 exit(1);
178 }
179
180 /*
181 * Determine if input is a pipe. 4.4BSD will set the SOCKET
182 * bit in the st_mode field for pipes. Fix this then.
183 */
184 if (lseek(fileno(tf[0].fp), (off_t)0, SEEK_CUR) == -1 &&
185 errno == ESPIPE) {
186 errno = 0;
187 fflag = 0; /* POSIX.2 requires this. */
188 }
189
190 if (rflag)
191 reverse(tf, 1, style, off);
192 else
193 forward(tf, 1, style, off);
194 }
195 exit(rval);
196 }
197
198 /*
199 * Convert the obsolete argument form into something that getopt can handle.
200 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't
201 * the option argument for a -b, -c or -n option gets converted.
202 */
203 static void
obsolete(char * argv[])204 obsolete(char *argv[])
205 {
206 char *ap, *p, *t;
207 size_t len;
208 char *start;
209
210 while ((ap = *++argv)) {
211 /* Return if "--" or not an option of any form. */
212 if (ap[0] != '-') {
213 if (ap[0] != '+')
214 return;
215 } else if (ap[1] == '-')
216 return;
217
218 switch(*++ap) {
219 /* Old-style option. */
220 case '0': case '1': case '2': case '3': case '4':
221 case '5': case '6': case '7': case '8': case '9':
222
223 /* Malloc space for dash, new option and argument. */
224 len = strlen(*argv);
225 if ((start = p = malloc(len + 4)) == NULL)
226 err(1, NULL);
227 *p++ = '-';
228
229 /*
230 * Go to the end of the option argument. Save off any
231 * trailing options (-3lf) and translate any trailing
232 * output style characters.
233 */
234 t = *argv + len - 1;
235 if (*t == 'f' || *t == 'r') {
236 *p++ = *t;
237 *t-- = '\0';
238 }
239 switch(*t) {
240 case 'b':
241 *p++ = 'b';
242 *t = '\0';
243 break;
244 case 'c':
245 *p++ = 'c';
246 *t = '\0';
247 break;
248 case 'l':
249 *t = '\0';
250 /* FALLTHROUGH */
251 case '0': case '1': case '2': case '3': case '4':
252 case '5': case '6': case '7': case '8': case '9':
253 *p++ = 'n';
254 break;
255 default:
256 errx(1, "illegal option -- %s", *argv);
257 }
258 *p++ = *argv[0];
259 (void)strlcpy(p, ap, start + len + 4 - p);
260 *argv = start;
261 continue;
262
263 /*
264 * Options w/ arguments, skip the argument and continue
265 * with the next option.
266 */
267 case 'b':
268 case 'c':
269 case 'n':
270 if (!ap[1])
271 ++argv;
272 /* FALLTHROUGH */
273 /* Options w/o arguments, continue with the next option. */
274 case 'f':
275 case 'r':
276 continue;
277
278 /* Illegal option, return and let getopt handle it. */
279 default:
280 return;
281 }
282 }
283 }
284
285 static void
usage(void)286 usage(void)
287 {
288 (void)fprintf(stderr,
289 "usage: tail [-f | -r] "
290 "[-b number | -c number | -n number | -number] [file ...]\n");
291 exit(1);
292 }
293