coreutils/tail.c - busybox - Git at Google

 /* vi: set sw=4 ts=4: */
 /*
  * Mini tail implementation for busybox
  *
  * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  *
  */

 /* 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 <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include "busybox.h"

 static const struct suffix_mult tail_suffixes[] = {
 	{ "b", 512 },
 	{ "k", 1024 },
 	{ "m", 1048576 },
 	{ NULL, 0 }
 };

 static int status
 #if EXIT_SUCCESS != 0
 	= EXIT_SUCCESS	/* If it is 0 (paranoid check), let bss initialize it. */
 #endif
 	;

 static void tail_xprint_header(const char *fmt, const char *filename)
 {
 	/* If we get an output error, there is really no sense in continuing. */
 	if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
 		bb_perror_nomsg_and_die();
 	}
 }

 /* len should probably be size_t */
 static void tail_xbb_full_write(const char *buf, size_t len)
 {
 	/* If we get a write error, there is really no sense in continuing. */
 	if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
 		bb_perror_nomsg_and_die();
 	}
 }

 static ssize_t tail_read(int fd, char *buf, size_t count)
 {
 	ssize_t r;

 	if ((r = safe_read(fd, buf, count)) < 0) {
 		bb_perror_msg("read");
 		status = EXIT_FAILURE;
 	}

 	return r;
 }

 static const char tail_opts[] =
 	"fn:c:"
 #ifdef CONFIG_FEATURE_FANCY_TAIL
 	"qs:v"
 #endif
 	;

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

 int tail_main(int argc, char **argv)
 {
 	long count = 10;
 	unsigned int sleep_period = 1;
 	int from_top = 0;
 	int follow = 0;
 	int header_threshhold = 1;
 	int count_bytes = 0;

 	char *tailbuf;
 	size_t tailbufsize;
 	int taillen = 0;
 	int newline = 0;

 	int *fds, nfiles, nread, nwrite, seen, i, opt;
 	char *s, *buf;
 	const char *fmt;

 	/* Allow legacy syntax of an initial numeric option without -n. */
 	if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
 			/* && (isdigit)(argv[1][1]) */
 			&& (((unsigned int)(argv[1][1] - '0')) <= 9))))
 	{
 		optind = 2;
 		optarg = argv[1];
 		goto GET_COUNT;
 	}

 	while ((opt = getopt(argc, argv, tail_opts)) > 0) {
 		switch (opt) {
 			case 'f':
 				follow = 1;
 				break;
 			case 'c':
 				count_bytes = 1;
 				/* FALLS THROUGH */
 			case 'n':
 			GET_COUNT:
 				count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
 				/* Note: Leading whitespace is an error trapped above. */
 				if (*optarg == '+') {
 					from_top = 1;
 				} else {
 					from_top = 0;
 				}
 				if (count < 0) {
 					count = -count;
 				}
 				break;
 #ifdef CONFIG_FEATURE_FANCY_TAIL
 			case 'q':
 				header_threshhold = INT_MAX;
 				break;
 			case 's':
 				sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
 				break;
 			case 'v':
 				header_threshhold = 0;
 				break;
 #endif
 			default:
 				bb_show_usage();
 		}
 	}

 	/* open all the files */
 	fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));

 	argv += optind;
 	nfiles = i = 0;

 	if ((argc -= optind) == 0) {
 		struct stat statbuf;

 		if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
 			follow = 0;
 		}
 		/* --argv; */
 		*argv = (char *) bb_msg_standard_input;
 		goto DO_STDIN;
 	}

 	do {
 		if ((argv[i][0] == '-') && !argv[i][1]) {
 		DO_STDIN:
 			fds[nfiles] = STDIN_FILENO;
 		} else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
 			bb_perror_msg("%s", argv[i]);
 			status = EXIT_FAILURE;
 			continue;
 		}
 		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) {	/* Each is 0 or 1, so true iff 0 < 1. */
 		/* Hence, !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;

 		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);
 					}
 				}
 				tail_xbb_full_write(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) {
 			tail_xbb_full_write(tailbuf, taillen);
 		}

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

 	buf = xrealloc(tailbuf, BUFSIZ);

 	fmt = NULL;

 	while (follow) {
 		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;
 				}
 				tail_xbb_full_write(buf, nread);
 			}
 		} while (++i < nfiles);
 	}

 	return status;
 }
	/* vi: set sw=4 ts=4: */
	/*
	* Mini tail implementation for busybox
	*
	* Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*
	*/

	/* 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 <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <ctype.h>
	#include <unistd.h>
	#include <fcntl.h>
	#include <sys/stat.h>
	#include "busybox.h"

	static const struct suffix_mult tail_suffixes[] = {
	{ "b", 512 },
	{ "k", 1024 },
	{ "m", 1048576 },
	{ NULL, 0 }
	};

	static int status
	#if EXIT_SUCCESS != 0
	= EXIT_SUCCESS /* If it is 0 (paranoid check), let bss initialize it. */
	#endif
	;

	static void tail_xprint_header(const char fmt, const char filename)
	{
	/* If we get an output error, there is really no sense in continuing. */
	if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
	bb_perror_nomsg_and_die();
	}
	}

	/* len should probably be size_t */
	static void tail_xbb_full_write(const char *buf, size_t len)
	{
	/* If we get a write error, there is really no sense in continuing. */
	if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
	bb_perror_nomsg_and_die();
	}
	}

	static ssize_t tail_read(int fd, char *buf, size_t count)
	{
	ssize_t r;

	if ((r = safe_read(fd, buf, count)) < 0) {
	bb_perror_msg("read");
	status = EXIT_FAILURE;
	}

	return r;
	}

	static const char tail_opts[] =
	"fn:c:"
	#ifdef CONFIG_FEATURE_FANCY_TAIL
	"qs:v"
	#endif
	;

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

	int tail_main(int argc, char **argv)
	{
	long count = 10;
	unsigned int sleep_period = 1;
	int from_top = 0;
	int follow = 0;
	int header_threshhold = 1;
	int count_bytes = 0;

	char *tailbuf;
	size_t tailbufsize;
	int taillen = 0;
	int newline = 0;

	int *fds, nfiles, nread, nwrite, seen, i, opt;
	char s, buf;
	const char *fmt;

	/* Allow legacy syntax of an initial numeric option without -n. */
	if (argc >=2 && ((argv[1][0] == '+') \|\| ((argv[1][0] == '-')
	/* && (isdigit)(argv[1][1]) */
	&& (((unsigned int)(argv[1][1] - '0')) <= 9))))
	{
	optind = 2;
	optarg = argv[1];
	goto GET_COUNT;
	}

	while ((opt = getopt(argc, argv, tail_opts)) > 0) {
	switch (opt) {
	case 'f':
	follow = 1;
	break;
	case 'c':
	count_bytes = 1;
	/* FALLS THROUGH */
	case 'n':
	GET_COUNT:
	count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
	/* Note: Leading whitespace is an error trapped above. */
	if (*optarg == '+') {
	from_top = 1;
	} else {
	from_top = 0;
	}
	if (count < 0) {
	count = -count;
	}
	break;
	#ifdef CONFIG_FEATURE_FANCY_TAIL
	case 'q':
	header_threshhold = INT_MAX;
	break;
	case 's':
	sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
	break;
	case 'v':
	header_threshhold = 0;
	break;
	#endif
	default:
	bb_show_usage();
	}
	}

	/* open all the files */
	fds = (int )xmalloc(sizeof(int) (argc - optind + 1));

	argv += optind;
	nfiles = i = 0;

	if ((argc -= optind) == 0) {
	struct stat statbuf;

	if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
	follow = 0;
	}
	/* --argv; */
	argv = (char ) bb_msg_standard_input;
	goto DO_STDIN;
	}

	do {
	if ((argv[i][0] == '-') && !argv[i][1]) {
	DO_STDIN:
	fds[nfiles] = STDIN_FILENO;
	} else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
	bb_perror_msg("%s", argv[i]);
	status = EXIT_FAILURE;
	continue;
	}
	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) { /* Each is 0 or 1, so true iff 0 < 1. */
	/* Hence, !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;

	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);
	}
	}
	tail_xbb_full_write(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) {
	tail_xbb_full_write(tailbuf, taillen);
	}

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

	buf = xrealloc(tailbuf, BUFSIZ);

	fmt = NULL;

	while (follow) {
	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;
	}
	tail_xbb_full_write(buf, nread);
	}
	} while (++i < nfiles);
	}

	return status;
	}