1/* vi: set sw=4 ts=4: */
2/*
3 * Mini tail implementation for busybox
4 *
5 * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
8 */
9
10/* BB_AUDIT SUSv3 compliant (need fancy for -c) */
11/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
12/* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
13
14/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
15 *
16 * Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
17 * Bugs fixed (although I may have forgotten one or two... it was pretty bad)
18 * 1) mixing printf/write without fflush()ing stdout
19 * 2) no check that any open files are present
20 * 3) optstring had -q taking an arg
21 * 4) no error checking on write in some cases, and a warning even then
22 * 5) q and s interaction bug
23 * 6) no check for lseek error
24 * 7) lseek attempted when count==0 even if arg was +0 (from top)
25 */
26
27#include "libbb.h"
28
29static const struct suffix_mult tail_suffixes[] = {
30	{ "b", 512 },
31	{ "k", 1024 },
32	{ "m", 1024*1024 },
33	{ }
34};
35
36struct globals {
37	bool status;
38};
39#define G (*(struct globals*)&bb_common_bufsiz1)
40
41static void tail_xprint_header(const char *fmt, const char *filename)
42{
43	if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
44		bb_perror_nomsg_and_die();
45}
46
47static ssize_t tail_read(int fd, char *buf, size_t count)
48{
49	ssize_t r;
50	off_t current, end;
51	struct stat sbuf;
52
53	end = current = lseek(fd, 0, SEEK_CUR);
54	if (!fstat(fd, &sbuf))
55		end = sbuf.st_size;
56	lseek(fd, end < current ? 0 : current, SEEK_SET);
57	r = safe_read(fd, buf, count);
58	if (r < 0) {
59		bb_perror_msg(bb_msg_read_error);
60		G.status = EXIT_FAILURE;
61	}
62
63	return r;
64}
65
66static const char header_fmt[] ALIGN1 = "\n==> %s <==\n";
67
68static unsigned eat_num(const char *p)
69{
70	if (*p == '-') p++;
71	else if (*p == '+') { p++; G.status = EXIT_FAILURE; }
72	return xatou_sfx(p, tail_suffixes);
73}
74
75int tail_main(int argc, char **argv);
76int tail_main(int argc, char **argv)
77{
78	unsigned count = 10;
79	unsigned sleep_period = 1;
80	bool from_top;
81	int header_threshhold = 1;
82	const char *str_c, *str_n;
83	USE_FEATURE_FANCY_TAIL(const char *str_s;)
84
85	char *tailbuf;
86	size_t tailbufsize;
87	int taillen = 0;
88	int newline = 0;
89	int nfiles, nread, nwrite, seen, i, opt;
90
91	int *fds;
92	char *s, *buf;
93	const char *fmt;
94
95#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
96	/* Allow legacy syntax of an initial numeric option without -n. */
97	if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
98	 && isdigit(argv[1][1])
99	) {
100		/* replacing arg[0] with "-n" can segfault, so... */
101		argv[1] = xasprintf("-n%s", argv[1]);
102	}
103#endif
104
105	opt = getopt32(argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"),
106			&str_c, &str_n USE_FEATURE_FANCY_TAIL(,&str_s));
107#define FOLLOW (opt & 0x1)
108#define COUNT_BYTES (opt & 0x2)
109	//if (opt & 0x1) // -f
110	if (opt & 0x2) count = eat_num(str_c); // -c
111	if (opt & 0x4) count = eat_num(str_n); // -n
112#if ENABLE_FEATURE_FANCY_TAIL
113	if (opt & 0x8) header_threshhold = INT_MAX; // -q
114	if (opt & 0x10) sleep_period = xatou(str_s); // -s
115	if (opt & 0x20) header_threshhold = 0; // -v
116#endif
117	argc -= optind;
118	argv += optind;
119	from_top = G.status;
120
121	/* open all the files */
122	fds = xmalloc(sizeof(int) * (argc + 1));
123	nfiles = i = 0;
124	G.status = EXIT_SUCCESS;
125	if (argc == 0) {
126		struct stat statbuf;
127
128		if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
129			opt &= ~1; /* clear FOLLOW */
130		}
131		*argv = (char *) bb_msg_standard_input;
132	}
133	do {
134		FILE* fil = fopen_or_warn_stdin(argv[i]);
135		if (!fil) {
136			G.status = EXIT_FAILURE;
137			continue;
138		}
139		fds[nfiles] = fileno(fil);
140		argv[nfiles++] = argv[i];
141	} while (++i < argc);
142
143	if (!nfiles)
144		bb_error_msg_and_die("no files");
145
146	tailbufsize = BUFSIZ;
147
148	/* tail the files */
149	if (!from_top && COUNT_BYTES) {
150		if (tailbufsize < count) {
151			tailbufsize = count + BUFSIZ;
152		}
153	}
154
155	buf = tailbuf = xmalloc(tailbufsize);
156
157	fmt = header_fmt + 1;	/* Skip header leading newline on first output. */
158	i = 0;
159	do {
160		/* Be careful.  It would be possible to optimize the count-bytes
161		 * case if the file is seekable.  If you do though, remember that
162		 * starting file position may not be the beginning of the file.
163		 * Beware of backing up too far.  See example in wc.c.
164		 */
165		if (!(count | from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
166			continue;
167		}
168
169		if (nfiles > header_threshhold) {
170			tail_xprint_header(fmt, argv[i]);
171			fmt = header_fmt;
172		}
173
174		buf = tailbuf;
175		taillen = 0;
176		seen = 1;
177		newline = 0;
178
179		while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
180			if (from_top) {
181				nwrite = nread;
182				if (seen < count) {
183					if (COUNT_BYTES) {
184						nwrite -= (count - seen);
185						seen = count;
186					} else {
187						s = buf;
188						do {
189							--nwrite;
190							if (*s++ == '\n' && ++seen == count) {
191								break;
192							}
193						} while (nwrite);
194					}
195				}
196				xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
197			} else if (count) {
198				if (COUNT_BYTES) {
199					taillen += nread;
200					if (taillen > count) {
201						memmove(tailbuf, tailbuf + taillen - count, count);
202						taillen = count;
203					}
204				} else {
205					int k = nread;
206					int nbuf = 0;
207
208					while (k) {
209						--k;
210						if (buf[k] == '\n') {
211							++nbuf;
212						}
213					}
214
215					if (newline + nbuf < count) {
216						newline += nbuf;
217						taillen += nread;
218					} else {
219						int extra = 0;
220
221						if (buf[nread-1] != '\n')
222							extra = 1;
223						k = newline + nbuf + extra - count;
224						s = tailbuf;
225						while (k) {
226							if (*s == '\n') {
227								--k;
228							}
229							++s;
230						}
231						taillen += nread - (s - tailbuf);
232						memmove(tailbuf, s, taillen);
233						newline = count - extra;
234					}
235					if (tailbufsize < taillen + BUFSIZ) {
236						tailbufsize = taillen + BUFSIZ;
237						tailbuf = xrealloc(tailbuf, tailbufsize);
238					}
239				}
240				buf = tailbuf + taillen;
241			}
242		}
243
244		if (!from_top) {
245			xwrite(STDOUT_FILENO, tailbuf, taillen);
246		}
247
248		taillen = 0;
249	} while (++i < nfiles);
250
251	buf = xrealloc(tailbuf, BUFSIZ);
252
253	fmt = NULL;
254
255	if (FOLLOW) while (1) {
256		sleep(sleep_period);
257		i = 0;
258		do {
259			if (nfiles > header_threshhold) {
260				fmt = header_fmt;
261			}
262			while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
263				if (fmt) {
264					tail_xprint_header(fmt, argv[i]);
265					fmt = NULL;
266				}
267				xwrite(STDOUT_FILENO, buf, nread);
268			}
269		} while (++i < nfiles);
270	}
271	if (ENABLE_FEATURE_CLEAN_UP) {
272		free(fds);
273	}
274	return G.status;
275}
276