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 "busybox.h"

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

static int status;

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, end;
	struct stat sbuf;

	end = current = lseek(fd, 0, SEEK_CUR);
	if (!fstat(fd, &sbuf))
		end = sbuf.st_size;
	lseek(fd, end < current ? 0 : current, SEEK_SET);
	r = safe_read(fd, buf, count);
	if (r < 0) {
		bb_perror_msg(bb_msg_read_error);
		status = EXIT_FAILURE;
	}

	return r;
}

static const char header_fmt[] = "\n==> %s <==\n";

int tail_main(int argc, char **argv)
{
	unsigned count = 10;
	unsigned sleep_period = 1;
	int from_top = 0;
	int header_threshhold = 1;
	const char *str_c, *str_n, *str_s;

	char *tailbuf;
	size_t tailbufsize;
	int taillen = 0;
	int newline = 0;
	int nfiles, nread, nwrite, seen, i, opt;

	int *fds;
	char *s, *buf;
	const char *fmt;

	void eat_num(const char *p) {
		if (*p == '-') p++;
		else if (*p == '+') { p++; from_top = 1; }
		count = xatou_sfx(p, tail_suffixes);
	}


#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
	/* Allow legacy syntax of an initial numeric option without -n. */
	if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
	 && isdigit(argv[1][1])
	) {
		argv[0] = "-n";
		argv--;
		argc++;
	}
#endif

	opt = getopt32(argc, argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"), &str_c, &str_n, &str_s);
#define FOLLOW (opt & 0x1)
#define COUNT_BYTES (opt & 0x2)
	//if (opt & 0x1) // -f
	if (opt & 0x2) eat_num(str_c); // -c
	if (opt & 0x4) eat_num(str_n); // -n
#if ENABLE_FEATURE_FANCY_TAIL
	if (opt & 0x8) header_threshhold = INT_MAX; // -q
	if (opt & 0x10) sleep_period = xatou(str_s); // -s
	if (opt & 0x20) header_threshhold = 0; // -v
#endif
	argc -= optind;
	argv += optind;

	/* open all the files */
	fds = xmalloc(sizeof(int) * (argc + 1));
	nfiles = i = 0;
	if (argc == 0) {
		struct stat statbuf;

		if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
			opt &= ~1; /* clear FOLLOW */
		}
		*argv = (char *) bb_msg_standard_input;
		goto DO_STDIN;
	}

	do {
		if (NOT_LONE_DASH(argv[i])) {
			fds[nfiles] = open(argv[i], O_RDONLY);
			if (fds[nfiles] < 0) {
				bb_perror_msg("%s", argv[i]);
				status = EXIT_FAILURE;
				continue;
			}
		} else {
 DO_STDIN:		/* "-" */
			fds[nfiles] = STDIN_FILENO;
		}
		argv[nfiles] = argv[i];
		++nfiles;
	} while (++i < argc);

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

	tailbufsize = BUFSIZ;

	/* tail the files */
	if (!from_top && COUNT_BYTES) {
		if (tailbufsize < count) {
			tailbufsize = count + BUFSIZ;
		}
	}

	buf = tailbuf = xmalloc(tailbufsize);

	fmt = header_fmt + 1;	/* Skip header leading newline on first output. */
	i = 0;
	do {
		/* Be careful.  It would be possible to optimize the count-bytes
		 * case if the file is seekable.  If you do though, remember that
		 * starting file position may not be the beginning of the file.
		 * Beware of backing up too far.  See example in wc.c.
		 */
		if (!(count | from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
			continue;
		}

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

		buf = tailbuf;
		taillen = 0;
		seen = 1;
		newline = 0;

		while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
			if (from_top) {
				nwrite = nread;
				if (seen < count) {
					if (COUNT_BYTES) {
						nwrite -= (count - seen);
						seen = count;
					} else {
						s = buf;
						do {
							--nwrite;
							if (*s++ == '\n' && ++seen == count) {
								break;
							}
						} while (nwrite);
					}
				}
				xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
			} else if (count) {
				if (COUNT_BYTES) {
					taillen += nread;
					if (taillen > count) {
						memmove(tailbuf, tailbuf + taillen - count, count);
						taillen = count;
					}
				} else {
					int k = nread;
					int nbuf = 0;

					while (k) {
						--k;
						if (buf[k] == '\n') {
							++nbuf;
						}
					}

					if (newline + nbuf < count) {
						newline += nbuf;
						taillen += nread;

					} else {
						int extra = 0;
						if (buf[nread-1] != '\n') {
							extra = 1;
						}

						k = newline + nbuf + extra - count;
						s = tailbuf;
						while (k) {
							if (*s == '\n') {
								--k;
							}
							++s;
						}

						taillen += nread - (s - tailbuf);
						memmove(tailbuf, s, taillen);
						newline = count - extra;
					}
					if (tailbufsize < taillen + BUFSIZ) {
						tailbufsize = taillen + BUFSIZ;
						tailbuf = xrealloc(tailbuf, tailbufsize);
					}
				}
				buf = tailbuf + taillen;
			}
		}

		if (!from_top) {
			xwrite(STDOUT_FILENO, tailbuf, taillen);
		}

		taillen = 0;
	} while (++i < nfiles);

	buf = xrealloc(tailbuf, BUFSIZ);

	fmt = NULL;

	if (FOLLOW) while (1) {
		sleep(sleep_period);
		i = 0;
		do {
			if (nfiles > header_threshhold) {
				fmt = header_fmt;
			}
			while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
				if (fmt) {
					tail_xprint_header(fmt, argv[i]);
					fmt = NULL;
				}
				xwrite(STDOUT_FILENO, buf, nread);
			}
		} while (++i < nfiles);
	}

	return status;
}
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 "busybox.h"
28
29	static const struct suffix_mult tail_suffixes[] = {
30	{ "b", 512 },
31	{ "k", 1024 },
32	{ "m", 1024*1024 },
33	{ NULL, 0 }
34	};
35
36	static int status;
37
38	static void tail_xprint_header(const char fmt, const char filename)
39	{
40	if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
41	bb_perror_nomsg_and_die();
42	}
43
44	static ssize_t tail_read(int fd, char *buf, size_t count)
45	{
46	ssize_t r;
47	off_t current, end;
48	struct stat sbuf;
49
50	end = current = lseek(fd, 0, SEEK_CUR);
51	if (!fstat(fd, &sbuf))
52	end = sbuf.st_size;
53	lseek(fd, end < current ? 0 : current, SEEK_SET);
54	r = safe_read(fd, buf, count);
55	if (r < 0) {
56	bb_perror_msg(bb_msg_read_error);
57	status = EXIT_FAILURE;
58	}
59
60	return r;
61	}
62
63	static const char header_fmt[] = "\n==> %s <==\n";
64
65	int tail_main(int argc, char **argv)
66	{
67	unsigned count = 10;
68	unsigned sleep_period = 1;
69	int from_top = 0;
70	int header_threshhold = 1;
71	const char str_c, str_n, *str_s;
72
73	char *tailbuf;
74	size_t tailbufsize;
75	int taillen = 0;
76	int newline = 0;
77	int nfiles, nread, nwrite, seen, i, opt;
78
79	int *fds;
80	char s, buf;
81	const char *fmt;
82
83	void eat_num(const char *p) {
84	if (*p == '-') p++;
85	else if (*p == '+') { p++; from_top = 1; }
86	count = xatou_sfx(p, tail_suffixes);
87	}
88
89
90	#if ENABLE_INCLUDE_SUSv2 \|\| ENABLE_FEATURE_FANCY_TAIL
91	/* Allow legacy syntax of an initial numeric option without -n. */
92	if (argc >= 2 && (argv[1][0] == '+' \|\| argv[1][0] == '-')
93	&& isdigit(argv[1][1])
94	) {
95	argv[0] = "-n";
96	argv--;
97	argc++;
98	}
99	#endif
100
101	opt = getopt32(argc, argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"), &str_c, &str_n, &str_s);
102	#define FOLLOW (opt & 0x1)
103	#define COUNT_BYTES (opt & 0x2)
104	//if (opt & 0x1) // -f
105	if (opt & 0x2) eat_num(str_c); // -c
106	if (opt & 0x4) eat_num(str_n); // -n
107	#if ENABLE_FEATURE_FANCY_TAIL
108	if (opt & 0x8) header_threshhold = INT_MAX; // -q
109	if (opt & 0x10) sleep_period = xatou(str_s); // -s
110	if (opt & 0x20) header_threshhold = 0; // -v
111	#endif
112	argc -= optind;
113	argv += optind;
114
115	/* open all the files */
116	fds = xmalloc(sizeof(int) * (argc + 1));
117	nfiles = i = 0;
118	if (argc == 0) {
119	struct stat statbuf;
120
121	if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
122	opt &= ~1; /* clear FOLLOW */
123	}
124	argv = (char ) bb_msg_standard_input;
125	goto DO_STDIN;
126	}
127
128	do {
129	if (NOT_LONE_DASH(argv[i])) {
130	fds[nfiles] = open(argv[i], O_RDONLY);
131	if (fds[nfiles] < 0) {
132	bb_perror_msg("%s", argv[i]);
133	status = EXIT_FAILURE;
134	continue;
135	}
136	} else {
137	DO_STDIN: /* "-" */
138	fds[nfiles] = STDIN_FILENO;
139	}
140	argv[nfiles] = argv[i];
141	++nfiles;
142	} while (++i < argc);
143
144	if (!nfiles)
145	bb_error_msg_and_die("no files");
146
147	tailbufsize = BUFSIZ;
148
149	/* tail the files */
150	if (!from_top && COUNT_BYTES) {
151	if (tailbufsize < count) {
152	tailbufsize = count + BUFSIZ;
153	}
154	}
155
156	buf = tailbuf = xmalloc(tailbufsize);
157
158	fmt = header_fmt + 1; /* Skip header leading newline on first output. */
159	i = 0;
160	do {
161	/* Be careful. It would be possible to optimize the count-bytes
162	* case if the file is seekable. If you do though, remember that
163	* starting file position may not be the beginning of the file.
164	* Beware of backing up too far. See example in wc.c.
165	*/
166	if (!(count \| from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
167	continue;
168	}
169
170	if (nfiles > header_threshhold) {
171	tail_xprint_header(fmt, argv[i]);
172	fmt = header_fmt;
173	}
174
175	buf = tailbuf;
176	taillen = 0;
177	seen = 1;
178	newline = 0;
179
180	while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
181	if (from_top) {
182	nwrite = nread;
183	if (seen < count) {
184	if (COUNT_BYTES) {
185	nwrite -= (count - seen);
186	seen = count;
187	} else {
188	s = buf;
189	do {
190	--nwrite;
191	if (*s++ == '\n' && ++seen == count) {
192	break;
193	}
194	} while (nwrite);
195	}
196	}
197	xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
198	} else if (count) {
199	if (COUNT_BYTES) {
200	taillen += nread;
201	if (taillen > count) {
202	memmove(tailbuf, tailbuf + taillen - count, count);
203	taillen = count;
204	}
205	} else {
206	int k = nread;
207	int nbuf = 0;
208
209	while (k) {
210	--k;
211	if (buf[k] == '\n') {
212	++nbuf;
213	}
214	}
215
216	if (newline + nbuf < count) {
217	newline += nbuf;
218	taillen += nread;
219
220	} else {
221	int extra = 0;
222	if (buf[nread-1] != '\n') {
223	extra = 1;
224	}
225
226	k = newline + nbuf + extra - count;
227	s = tailbuf;
228	while (k) {
229	if (*s == '\n') {
230	--k;
231	}
232	++s;
233	}
234
235	taillen += nread - (s - tailbuf);
236	memmove(tailbuf, s, taillen);
237	newline = count - extra;
238	}
239	if (tailbufsize < taillen + BUFSIZ) {
240	tailbufsize = taillen + BUFSIZ;
241	tailbuf = xrealloc(tailbuf, tailbufsize);
242	}
243	}
244	buf = tailbuf + taillen;
245	}
246	}
247
248	if (!from_top) {
249	xwrite(STDOUT_FILENO, tailbuf, taillen);
250	}
251
252	taillen = 0;
253	} while (++i < nfiles);
254
255	buf = xrealloc(tailbuf, BUFSIZ);
256
257	fmt = NULL;
258
259	if (FOLLOW) while (1) {
260	sleep(sleep_period);
261	i = 0;
262	do {
263	if (nfiles > header_threshhold) {
264	fmt = header_fmt;
265	}
266	while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
267	if (fmt) {
268	tail_xprint_header(fmt, argv[i]);
269	fmt = NULL;
270	}
271	xwrite(STDOUT_FILENO, buf, nread);
272	}
273	} while (++i < nfiles);
274	}
275
276	return status;
277	}