/* 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 }, { } }; struct globals { bool status; }; #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; /* (A good comment is missing here) */ current = lseek(fd, 0, SEEK_CUR); /* /proc files report zero st_size, don't lseek them. */ if (fstat(fd, &sbuf) == 0 && sbuf.st_size) if (sbuf.st_size < current) lseek(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; } static const char header_fmt[] ALIGN1 = "\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; int header_threshhold = 1; const char *str_c, *str_n; char *tailbuf; size_t tailbufsize; int taillen = 0; int newlines_seen = 0; int nfiles, nread, nwrite, i, opt; unsigned seen; int *fds; char *s, *buf; 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 IF_FEATURE_FANCY_TAIL(opt_complementary = "s+";) /* -s N */ opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:v"), &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 if (opt & 0x8) header_threshhold = INT_MAX; // -q if (opt & 0x20) header_threshhold = 0; // -v #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(int) * (argc + 1)); if (!argv[0]) { struct stat statbuf; if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) { opt &= ~1; /* clear FOLLOW */ } *argv = (char *) bb_msg_standard_input; } nfiles = i = 0; do { int fd = open_or_warn_stdin(argv[i]); if (fd < 0) { 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 + 1; /* Skip header leading newline on first output. */ i = 0; do { if (nfiles > header_threshhold) { tail_xprint_header(fmt, argv[i]); fmt = header_fmt; } /* 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_BYTES && !from_top) { off_t current = lseek(fds[i], 0, SEEK_END); if (current > 0) { if (count == 0) continue; /* showing zero lines is easy :) */ current -= count; if (current < 0) current = 0; xlseek(fds[i], current, SEEK_SET); bb_copyfd_size(fds[i], STDOUT_FILENO, count); continue; } } buf = tailbuf; taillen = 0; seen = 1; newlines_seen = 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 > (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'); 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); 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, BUFSIZ)) > 0) { if (fmt) { tail_xprint_header(fmt, argv[i]); fmt = NULL; } xwrite(STDOUT_FILENO, buf, nread); } } while (++i < nfiles); } if (ENABLE_FEATURE_CLEAN_UP) { free(fds); } return G.status; }