busybox/coreutils/tail.c

/* vi: set sw=4 ts=4: */
/*
 * Mini tail implementation for busybox
 *
 * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/* BB_AUDIT SUSv3 compliant (need fancy for -c) */
/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */

/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
 *
 * Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
 * Bugs fixed (although I may have forgotten one or two... it was pretty bad)
 * 1) mixing printf/write without fflush()ing stdout
 * 2) no check that any open files are present
 * 3) optstring had -q taking an arg
 * 4) no error checking on write in some cases, and a warning even then
 * 5) q and s interaction bug
 * 6) no check for lseek error
 * 7) lseek attempted when count==0 even if arg was +0 (from top)
 */

#include "libbb.h"

static const struct suffix_mult tail_suffixes[] = {
	{ "b", 512 },
	{ "k", 1024 },
	{ "m", 1024*1024 },
	{ "", 0 }
};

struct globals {
	bool status;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)

static void tail_xprint_header(const char *fmt, const char *filename)
{
	if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
		bb_perror_nomsg_and_die();
}

static ssize_t tail_read(int fd, char *buf, size_t count)
{
	ssize_t r;
	off_t current;
	struct stat sbuf;

	/* /proc files report zero st_size, don't lseek them. */
	if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
		current = lseek(fd, 0, SEEK_CUR);
		if (sbuf.st_size < current)
			xlseek(fd, 0, SEEK_SET);
	}

	r = full_read(fd, buf, count);
	if (r < 0) {
		bb_perror_msg(bb_msg_read_error);
		G.status = EXIT_FAILURE;
	}

	return r;
}

#define header_fmt_str "\n==> %s <==\n"

static unsigned eat_num(const char *p)
{
	if (*p == '-')
		p++;
	else if (*p == '+') {
		p++;
		G.status = 1; /* mark that we saw "+" */
	}
	return xatou_sfx(p, tail_suffixes);
}

int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tail_main(int argc, char **argv)
{
	unsigned count = 10;
	unsigned sleep_period = 1;
	bool from_top;
	const char *str_c, *str_n;

	char *tailbuf;
	size_t tailbufsize;
	unsigned header_threshhold = 1;
	unsigned nfiles;
	int i, opt;

	int *fds;
	const char *fmt;

#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
	/* Allow legacy syntax of an initial numeric option without -n. */
	if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-')
	 && isdigit(argv[1][1])
	) {
		count = eat_num(argv[1]);
		argv++;
		argc--;
	}
#endif

	/* -s NUM, -F imlies -f */
	IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";)
	opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"),
			&str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period));
#define FOLLOW (opt & 0x1)
#define COUNT_BYTES (opt & 0x2)
	//if (opt & 0x1) // -f
	if (opt & 0x2) count = eat_num(str_c); // -c
	if (opt & 0x4) count = eat_num(str_n); // -n
#if ENABLE_FEATURE_FANCY_TAIL
	/* q: make it impossible for nfiles to be > header_threshhold */
	if (opt & 0x8) header_threshhold = UINT_MAX; // -q
	//if (opt & 0x10) // -s
	if (opt & 0x20) header_threshhold = 0; // -v
# define FOLLOW_RETRY (opt & 0x40)
#else
# define FOLLOW_RETRY 0
#endif
	argc -= optind;
	argv += optind;
	from_top = G.status; /* 1 if there was "-c +N" or "-n +N" */
	G.status = EXIT_SUCCESS;

	/* open all the files */
	fds = xmalloc(sizeof(fds[0]) * (argc + 1));
	if (!argv[0]) {
		struct stat statbuf;

		if (fstat(STDIN_FILENO, &statbuf) == 0
		 && S_ISFIFO(statbuf.st_mode)
		) {
			opt &= ~1; /* clear FOLLOW */
		}
		argv[0] = (char *) bb_msg_standard_input;
	}
	nfiles = i = 0;
	do {
		int fd = open_or_warn_stdin(argv[i]);
		if (fd < 0 && !FOLLOW_RETRY) {
			G.status = EXIT_FAILURE;
			continue;
		}
		fds[nfiles] = fd;
		argv[nfiles++] = argv[i];
	} while (++i < argc);

	if (!nfiles)
		bb_error_msg_and_die("no files");

	/* prepare the buffer */
	tailbufsize = BUFSIZ;
	if (!from_top && COUNT_BYTES) {
		if (tailbufsize < count + BUFSIZ) {
			tailbufsize = count + BUFSIZ;
		}
	}
	tailbuf = xmalloc(tailbufsize);

	/* tail the files */
	fmt = header_fmt_str + 1; /* skip header leading newline on first output */
	i = 0;
	do {
		char *buf;
		int taillen;
		int newlines_seen;
		unsigned seen;
		int nread;
		int fd = fds[i];

		if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
			continue; /* may happen with -E */

		if (nfiles > header_threshhold) {
			tail_xprint_header(fmt, argv[i]);
			fmt = header_fmt_str;
		}

		if (!from_top) {
			off_t current = lseek(fd, 0, SEEK_END);
			if (current > 0) {
				unsigned off;
				if (COUNT_BYTES) {
				/* Optimizing count-bytes case if the file is seekable.
				 * Beware of backing up too far.
				 * Also we exclude files with size 0 (because of /proc/xxx) */
					if (count == 0)
						continue; /* showing zero bytes is easy :) */
					current -= count;
					if (current < 0)
						current = 0;
					xlseek(fd, current, SEEK_SET);
					bb_copyfd_size(fd, STDOUT_FILENO, count);
					continue;
				}
#if 1 /* This is technically incorrect for *LONG* strings, but very useful */
				/* Optimizing count-lines case if the file is seekable.
				 * We assume the lines are <64k.
				 * (Users complain that tail takes too long
				 * on multi-gigabyte files) */
				off = (count | 0xf); /* for small counts, be more paranoid */
				if (off > (INT_MAX / (64*1024)))
					off = (INT_MAX / (64*1024));
				current -= off * (64*1024);
				if (current < 0)
					current = 0;
				xlseek(fd, current, SEEK_SET);
#endif
			}
		}

		buf = tailbuf;
		taillen = 0;
		/* "We saw 1st line/byte".
		 * Used only by +N code ("start from Nth", 1-based): */
		seen = 1;
		newlines_seen = 0;
		while ((nread = tail_read(fd, buf, tailbufsize-taillen)) > 0) {
			if (from_top) {
				int nwrite = nread;
				if (seen < count) {
					/* We need to skip a few more bytes/lines */
					if (COUNT_BYTES) {
						nwrite -= (count - seen);
						seen = count;
					} else {
						char *s = buf;
						do {
							--nwrite;
							if (*s++ == '\n' && ++seen == count) {
								break;
							}
						} while (nwrite);
					}
				}
				if (nwrite > 0)
					xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
			} else if (count) {
				if (COUNT_BYTES) {
					taillen += nread;
					if (taillen > (int)count) {
						memmove(tailbuf, tailbuf + taillen - count, count);
						taillen = count;
					}
				} else {
					int k = nread;
					int newlines_in_buf = 0;

					do { /* count '\n' in last read */
						k--;
						if (buf[k] == '\n') {
							newlines_in_buf++;
						}
					} while (k);

					if (newlines_seen + newlines_in_buf < (int)count) {
						newlines_seen += newlines_in_buf;
						taillen += nread;
					} else {
						int extra = (buf[nread-1] != '\n');
						char *s;

						k = newlines_seen + newlines_in_buf + extra - count;
						s = tailbuf;
						while (k) {
							if (*s == '\n') {
								k--;
							}
							s++;
						}
						taillen += nread - (s - tailbuf);
						memmove(tailbuf, s, taillen);
						newlines_seen = count - extra;
					}
					if (tailbufsize < (size_t)taillen + BUFSIZ) {
						tailbufsize = taillen + BUFSIZ;
						tailbuf = xrealloc(tailbuf, tailbufsize);
					}
				}
				buf = tailbuf + taillen;
			}
		} /* while (tail_read() > 0) */
		if (!from_top) {
			xwrite(STDOUT_FILENO, tailbuf, taillen);
		}
	} while (++i < nfiles);

	tailbuf = xrealloc(tailbuf, BUFSIZ);

	fmt = NULL;

	if (FOLLOW) while (1) {
		sleep(sleep_period);

		i = 0;
		do {
			int nread;
			const char *filename = argv[i];
			int fd = fds[i];

			if (FOLLOW_RETRY) {
				struct stat sbuf, fsbuf;

				if (fd < 0
				 || fstat(fd, &fsbuf) < 0
				 || stat(filename, &sbuf) < 0
				 || fsbuf.st_dev != sbuf.st_dev
				 || fsbuf.st_ino != sbuf.st_ino
				) {
					int new_fd;

					if (fd >= 0)
						close(fd);
					new_fd = open(filename, O_RDONLY);
					if (new_fd >= 0) {
						bb_error_msg("%s has %s; following end of new file",
							filename, (fd < 0) ? "appeared" : "been replaced"
						);
					} else if (fd >= 0) {
						bb_perror_msg("%s has become inaccessible", filename);
					}
					fds[i] = fd = new_fd;
				}
			}
			if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
				continue;
			if (nfiles > header_threshhold) {
				fmt = header_fmt_str;
			}
			while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) {
				if (fmt) {
					tail_xprint_header(fmt, filename);
					fmt = NULL;
				}
				xwrite(STDOUT_FILENO, tailbuf, nread);
			}
		} while (++i < nfiles);
	}
	if (ENABLE_FEATURE_CLEAN_UP) {
		free(fds);
	}
	return G.status;
}
1	niro	532	/* 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	niro	816	#include "libbb.h"
28	niro	532
29			static const struct suffix_mult tail_suffixes[] = {
30			{ "b", 512 },
31			{ "k", 1024 },
32			{ "m", 1024*1024 },
33	niro	984	{ "", 0 }
34	niro	532	};
35
36	niro	816	struct globals {
37			bool status;
38	niro	1123	} FIX_ALIASING;
39	niro	816	#define G ((struct globals)&bb_common_bufsiz1)
40	niro	532
41			static 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
47			static ssize_t tail_read(int fd, char *buf, size_t count)
48			{
49			ssize_t r;
50	niro	816	off_t current;
51	niro	532	struct stat sbuf;
52
53	niro	816	/* /proc files report zero st_size, don't lseek them. */
54	niro	984	if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
55			current = lseek(fd, 0, SEEK_CUR);
56	niro	816	if (sbuf.st_size < current)
57	niro	984	xlseek(fd, 0, SEEK_SET);
58			}
59	niro	816
60			r = full_read(fd, buf, count);
61	niro	532	if (r < 0) {
62			bb_perror_msg(bb_msg_read_error);
63	niro	816	G.status = EXIT_FAILURE;
64	niro	532	}
65
66			return r;
67			}
68
69	niro	1123	#define header_fmt_str "\n==> %s <==\n"
70	niro	532
71	niro	816	static unsigned eat_num(const char *p)
72			{
73			if (*p == '-')
74			p++;
75			else if (*p == '+') {
76			p++;
77			G.status = 1; /* mark that we saw "+" */
78			}
79			return xatou_sfx(p, tail_suffixes);
80			}
81
82			int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
83	niro	532	int tail_main(int argc, char **argv)
84			{
85			unsigned count = 10;
86			unsigned sleep_period = 1;
87	niro	816	bool from_top;
88			const char str_c, str_n;
89	niro	532
90			char *tailbuf;
91			size_t tailbufsize;
92	niro	984	unsigned header_threshhold = 1;
93			unsigned nfiles;
94			int i, opt;
95	niro	532
96			int *fds;
97			const char *fmt;
98
99			#if ENABLE_INCLUDE_SUSv2 \|\| ENABLE_FEATURE_FANCY_TAIL
100			/* Allow legacy syntax of an initial numeric option without -n. */
101	niro	816	if (argv[1] && (argv[1][0] == '+' \|\| argv[1][0] == '-')
102	niro	532	&& isdigit(argv[1][1])
103			) {
104	niro	816	count = eat_num(argv[1]);
105			argv++;
106			argc--;
107	niro	532	}
108			#endif
109
110	niro	984	/* -s NUM, -F imlies -f */
111			IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";)
112			opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"),
113			&str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period));
114	niro	532	#define FOLLOW (opt & 0x1)
115			#define COUNT_BYTES (opt & 0x2)
116			//if (opt & 0x1) // -f
117	niro	816	if (opt & 0x2) count = eat_num(str_c); // -c
118			if (opt & 0x4) count = eat_num(str_n); // -n
119	niro	532	#if ENABLE_FEATURE_FANCY_TAIL
120	niro	984	/* q: make it impossible for nfiles to be > header_threshhold */
121			if (opt & 0x8) header_threshhold = UINT_MAX; // -q
122			//if (opt & 0x10) // -s
123	niro	532	if (opt & 0x20) header_threshhold = 0; // -v
124	niro	984	# define FOLLOW_RETRY (opt & 0x40)
125			#else
126			# define FOLLOW_RETRY 0
127	niro	532	#endif
128			argc -= optind;
129			argv += optind;
130	niro	816	from_top = G.status; /* 1 if there was "-c +N" or "-n +N" */
131			G.status = EXIT_SUCCESS;
132	niro	532
133			/* open all the files */
134	niro	984	fds = xmalloc(sizeof(fds[0]) * (argc + 1));
135	niro	816	if (!argv[0]) {
136	niro	532	struct stat statbuf;
137
138	niro	984	if (fstat(STDIN_FILENO, &statbuf) == 0
139			&& S_ISFIFO(statbuf.st_mode)
140			) {
141	niro	532	opt &= ~1; /* clear FOLLOW */
142			}
143	niro	984	argv[0] = (char *) bb_msg_standard_input;
144	niro	532	}
145	niro	816	nfiles = i = 0;
146	niro	532	do {
147	niro	816	int fd = open_or_warn_stdin(argv[i]);
148	niro	984	if (fd < 0 && !FOLLOW_RETRY) {
149	niro	816	G.status = EXIT_FAILURE;
150			continue;
151	niro	532	}
152	niro	816	fds[nfiles] = fd;
153			argv[nfiles++] = argv[i];
154	niro	532	} while (++i < argc);
155
156			if (!nfiles)
157			bb_error_msg_and_die("no files");
158
159	niro	816	/* prepare the buffer */
160	niro	532	tailbufsize = BUFSIZ;
161			if (!from_top && COUNT_BYTES) {
162	niro	816	if (tailbufsize < count + BUFSIZ) {
163	niro	532	tailbufsize = count + BUFSIZ;
164			}
165			}
166	niro	816	tailbuf = xmalloc(tailbufsize);
167	niro	532
168	niro	816	/* tail the files */
169	niro	1123	fmt = header_fmt_str + 1; /* skip header leading newline on first output */
170	niro	532	i = 0;
171			do {
172	niro	984	char *buf;
173			int taillen;
174			int newlines_seen;
175			unsigned seen;
176			int nread;
177			int fd = fds[i];
178
179			if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
180			continue; /* may happen with -E */
181
182	niro	532	if (nfiles > header_threshhold) {
183			tail_xprint_header(fmt, argv[i]);
184	niro	1123	fmt = header_fmt_str;
185	niro	532	}
186
187	niro	984	if (!from_top) {
188			off_t current = lseek(fd, 0, SEEK_END);
189	niro	816	if (current > 0) {
190	niro	984	unsigned off;
191			if (COUNT_BYTES) {
192			/* Optimizing count-bytes case if the file is seekable.
193			* Beware of backing up too far.
194			* Also we exclude files with size 0 (because of /proc/xxx) */
195			if (count == 0)
196			continue; /* showing zero bytes is easy :) */
197			current -= count;
198			if (current < 0)
199			current = 0;
200			xlseek(fd, current, SEEK_SET);
201			bb_copyfd_size(fd, STDOUT_FILENO, count);
202			continue;
203			}
204			#if 1 /* This is technically incorrect for LONG strings, but very useful */
205			/* Optimizing count-lines case if the file is seekable.
206			* We assume the lines are <64k.
207			* (Users complain that tail takes too long
208			* on multi-gigabyte files) */
209			off = (count \| 0xf); /* for small counts, be more paranoid */
210			if (off > (INT_MAX / (64*1024)))
211			off = (INT_MAX / (64*1024));
212			current -= off * (64*1024);
213	niro	816	if (current < 0)
214			current = 0;
215	niro	984	xlseek(fd, current, SEEK_SET);
216			#endif
217	niro	816	}
218			}
219
220	niro	532	buf = tailbuf;
221			taillen = 0;
222	niro	984	/* "We saw 1st line/byte".
223			* Used only by +N code ("start from Nth", 1-based): */
224	niro	532	seen = 1;
225	niro	816	newlines_seen = 0;
226	niro	984	while ((nread = tail_read(fd, buf, tailbufsize-taillen)) > 0) {
227	niro	532	if (from_top) {
228	niro	984	int nwrite = nread;
229	niro	532	if (seen < count) {
230	niro	984	/* We need to skip a few more bytes/lines */
231	niro	532	if (COUNT_BYTES) {
232			nwrite -= (count - seen);
233			seen = count;
234			} else {
235	niro	984	char *s = buf;
236	niro	532	do {
237			--nwrite;
238			if (*s++ == '\n' && ++seen == count) {
239			break;
240			}
241			} while (nwrite);
242			}
243			}
244	niro	984	if (nwrite > 0)
245			xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
246	niro	532	} else if (count) {
247			if (COUNT_BYTES) {
248			taillen += nread;
249	niro	816	if (taillen > (int)count) {
250	niro	532	memmove(tailbuf, tailbuf + taillen - count, count);
251			taillen = count;
252			}
253			} else {
254			int k = nread;
255	niro	816	int newlines_in_buf = 0;
256	niro	532
257	niro	816	do { /* count '\n' in last read */
258			k--;
259	niro	532	if (buf[k] == '\n') {
260	niro	816	newlines_in_buf++;
261	niro	532	}
262	niro	816	} while (k);
263	niro	532
264	niro	816	if (newlines_seen + newlines_in_buf < (int)count) {
265			newlines_seen += newlines_in_buf;
266	niro	532	taillen += nread;
267			} else {
268	niro	816	int extra = (buf[nread-1] != '\n');
269	niro	984	char *s;
270	niro	532
271	niro	816	k = newlines_seen + newlines_in_buf + extra - count;
272	niro	532	s = tailbuf;
273			while (k) {
274			if (*s == '\n') {
275	niro	816	k--;
276	niro	532	}
277	niro	816	s++;
278	niro	532	}
279			taillen += nread - (s - tailbuf);
280			memmove(tailbuf, s, taillen);
281	niro	816	newlines_seen = count - extra;
282	niro	532	}
283	niro	816	if (tailbufsize < (size_t)taillen + BUFSIZ) {
284	niro	532	tailbufsize = taillen + BUFSIZ;
285			tailbuf = xrealloc(tailbuf, tailbufsize);
286			}
287			}
288			buf = tailbuf + taillen;
289			}
290	niro	816	} /* while (tail_read() > 0) */
291	niro	532	if (!from_top) {
292			xwrite(STDOUT_FILENO, tailbuf, taillen);
293			}
294			} while (++i < nfiles);
295
296	niro	984	tailbuf = xrealloc(tailbuf, BUFSIZ);
297	niro	532
298			fmt = NULL;
299
300			if (FOLLOW) while (1) {
301			sleep(sleep_period);
302	niro	984
303	niro	532	i = 0;
304			do {
305	niro	984	int nread;
306			const char *filename = argv[i];
307			int fd = fds[i];
308
309			if (FOLLOW_RETRY) {
310			struct stat sbuf, fsbuf;
311
312			if (fd < 0
313			\|\| fstat(fd, &fsbuf) < 0
314			\|\| stat(filename, &sbuf) < 0
315			\|\| fsbuf.st_dev != sbuf.st_dev
316			\|\| fsbuf.st_ino != sbuf.st_ino
317			) {
318			int new_fd;
319
320			if (fd >= 0)
321			close(fd);
322			new_fd = open(filename, O_RDONLY);
323			if (new_fd >= 0) {
324			bb_error_msg("%s has %s; following end of new file",
325			filename, (fd < 0) ? "appeared" : "been replaced"
326			);
327			} else if (fd >= 0) {
328			bb_perror_msg("%s has become inaccessible", filename);
329			}
330			fds[i] = fd = new_fd;
331			}
332			}
333			if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
334			continue;
335	niro	532	if (nfiles > header_threshhold) {
336	niro	1123	fmt = header_fmt_str;
337	niro	532	}
338	niro	984	while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) {
339	niro	532	if (fmt) {
340	niro	984	tail_xprint_header(fmt, filename);
341	niro	532	fmt = NULL;
342			}
343	niro	984	xwrite(STDOUT_FILENO, tailbuf, nread);
344	niro	532	}
345			} while (++i < nfiles);
346			}
347	niro	816	if (ENABLE_FEATURE_CLEAN_UP) {
348			free(fds);
349			}
350			return G.status;
351	niro	532	}