/* vi: set sw=4 ts=4: */ /* * Mini tail implementation for busybox * * Copyright (C) 2001 by Matt Kraai * * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ /* 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) */ //kbuild:lib-$(CONFIG_TAIL) += tail.o //usage:#define tail_trivial_usage //usage: "[OPTIONS] [FILE]..." //usage:#define tail_full_usage "\n\n" //usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n" //usage: "With more than one FILE, precede each with a filename header.\n" //usage: "\n -f Print data as file grows" //usage: "\n -c [+]N[kbm] Print last N bytes" //usage: "\n -n N[kbm] Print last N lines" //usage: "\n -n +N[kbm] Start on Nth line and print the rest" //usage: IF_FEATURE_FANCY_TAIL( //usage: "\n -q Never print headers" //usage: "\n -s SECONDS Wait SECONDS between reads with -f" //usage: "\n -v Always print headers" //usage: "\n -F Same as -f, but keep retrying" //usage: "\n" //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)." //usage: ) //usage: //usage:#define tail_example_usage //usage: "$ tail -n 1 /etc/resolv.conf\n" //usage: "nameserver 10.0.0.1\n" #include "libbb.h" #include "common_bufsiz.h" struct globals { bool from_top; bool exitcode; } FIX_ALIASING; #define G (*(struct globals*)bb_common_bufsiz1) #define INIT_G() do { setup_common_bufsiz(); } while (0) 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; r = full_read(fd, buf, count); if (r < 0) { bb_perror_msg(bb_msg_read_error); G.exitcode = 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.from_top = 1; } return xatou_sfx(p, bkm_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; 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; int prev_fd; INIT_G(); #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; /* 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.exitcode = 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 (!G.from_top && COUNT_BYTES) { if (tailbufsize < count + BUFSIZ) { tailbufsize = count + BUFSIZ; } } /* tail -c1024m REGULAR_FILE doesn't really need 1G mem block. * (In fact, it doesn't need ANY memory). So delay allocation. */ tailbuf = NULL; /* tail the files */ fmt = header_fmt_str + 1; /* skip leading newline in the header on the 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 -F */ if (nfiles > header_threshhold) { tail_xprint_header(fmt, argv[i]); fmt = header_fmt_str; } if (!G.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 } } if (!tailbuf) tailbuf = xmalloc(tailbufsize); 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 (G.from_top) { int nwrite = nread; if (seen < count) { /* We need to skip a few more bytes/lines */ if (COUNT_BYTES) { nwrite -= (count - seen); seen += nread; } 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 (!G.from_top) { xwrite(STDOUT_FILENO, tailbuf, taillen); } } while (++i < nfiles); prev_fd = fds[i-1]; 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; } for (;;) { /* tail -f keeps following files even if they are truncated */ struct stat sbuf; /* /proc files report zero st_size, don't lseek them */ if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) { off_t current = lseek(fd, 0, SEEK_CUR); if (sbuf.st_size < current) xlseek(fd, 0, SEEK_SET); } nread = tail_read(fd, tailbuf, BUFSIZ); if (nread <= 0) break; if (fmt && (fd != prev_fd)) { tail_xprint_header(fmt, filename); fmt = NULL; prev_fd = fd; } xwrite(STDOUT_FILENO, tailbuf, nread); } } while (++i < nfiles); } /* while (1) */ if (ENABLE_FEATURE_CLEAN_UP) { free(fds); free(tailbuf); } return G.exitcode; }