X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=coreutils%2Ftail.c;h=e352ab627b2e86b9e45c6ae59b1b17e4b0dd6ff1;hb=2a17fbe88a0cc064248db4ce8939f0fbc357922d;hp=5f98bff820ee292cb6aefba69abf657f499fbb26;hpb=a43df64eec6d02812b40d7e01edbeb47539866db;p=oweals%2Fbusybox.git diff --git a/coreutils/tail.c b/coreutils/tail.c index 5f98bff82..e352ab627 100644 --- a/coreutils/tail.c +++ b/coreutils/tail.c @@ -4,7 +4,7 @@ * * Copyright (C) 2001 by Matt Kraai * - * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. + * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ /* BB_AUDIT SUSv3 compliant (need fancy for -c) */ @@ -24,19 +24,38 @@ * 7) lseek attempted when count==0 even if arg was +0 (from top) */ -#include "libbb.h" +//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" -static const struct suffix_mult tail_suffixes[] = { - { "b", 512 }, - { "k", 1024 }, - { "m", 1024*1024 }, - { } -}; +#include "libbb.h" struct globals { - bool status; -}; + bool from_top; + bool exitcode; +} FIX_ALIASING; #define G (*(struct globals*)&bb_common_bufsiz1) +#define INIT_G() do { } while (0) static void tail_xprint_header(const char *fmt, const char *filename) { @@ -47,26 +66,17 @@ static void tail_xprint_header(const char *fmt, const char *filename) 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) { - current = lseek(fd, 0, SEEK_CUR); - 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; + G.exitcode = EXIT_FAILURE; } return r; } -static const char header_fmt[] ALIGN1 = "\n==> %s <==\n"; +#define header_fmt_str "\n==> %s <==\n" static unsigned eat_num(const char *p) { @@ -74,9 +84,9 @@ static unsigned eat_num(const char *p) p++; else if (*p == '+') { p++; - G.status = 1; /* mark that we saw "+" */ + G.from_top = 1; } - return xatou_sfx(p, tail_suffixes); + return xatou_sfx(p, bkm_suffixes); } int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; @@ -84,7 +94,6 @@ 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; @@ -95,6 +104,9 @@ int tail_main(int argc, char **argv) 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. */ @@ -127,8 +139,6 @@ int tail_main(int argc, char **argv) #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)); @@ -146,7 +156,7 @@ int tail_main(int argc, char **argv) do { int fd = open_or_warn_stdin(argv[i]); if (fd < 0 && !FOLLOW_RETRY) { - G.status = EXIT_FAILURE; + G.exitcode = EXIT_FAILURE; continue; } fds[nfiles] = fd; @@ -158,15 +168,19 @@ int tail_main(int argc, char **argv) /* prepare the buffer */ tailbufsize = BUFSIZ; - if (!from_top && COUNT_BYTES) { + if (!G.from_top && COUNT_BYTES) { if (tailbufsize < count + BUFSIZ) { tailbufsize = count + BUFSIZ; } } - tailbuf = xmalloc(tailbufsize); + /* 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 + 1; /* skip header leading newline on first output */ + + fmt = header_fmt_str + 1; /* skip leading newline in the header on the first output */ i = 0; do { char *buf; @@ -174,46 +188,66 @@ int tail_main(int argc, char **argv) int newlines_seen; unsigned seen; int nread; + int fd = fds[i]; - if (ENABLE_FEATURE_FANCY_TAIL && fds[i] < 0) - continue; /* may happen with -E */ + 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; + fmt = header_fmt_str; } - /* 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 (!G.from_top) { + off_t current = lseek(fd, 0, SEEK_END); if (current > 0) { - if (count == 0) - continue; /* showing zero bytes is easy :) */ - current -= count; + 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(fds[i], current, SEEK_SET); - bb_copyfd_size(fds[i], STDOUT_FILENO, count); - continue; + 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) */ + * Used only by +N code ("start from Nth", 1-based): */ seen = 1; newlines_seen = 0; - while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) { - if (from_top) { + 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 = count; + seen += nread; } else { char *s = buf; do { @@ -224,7 +258,8 @@ int tail_main(int argc, char **argv) } while (nwrite); } } - xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite); + if (nwrite > 0) + xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite); } else if (count) { if (COUNT_BYTES) { taillen += nread; @@ -270,10 +305,11 @@ int tail_main(int argc, char **argv) buf = tailbuf + taillen; } } /* while (tail_read() > 0) */ - if (!from_top) { + if (!G.from_top) { xwrite(STDOUT_FILENO, tailbuf, taillen); } } while (++i < nfiles); + prev_fd = fds[i-1]; tailbuf = xrealloc(tailbuf, BUFSIZ); @@ -315,19 +351,34 @@ int tail_main(int argc, char **argv) if (ENABLE_FEATURE_FANCY_TAIL && fd < 0) continue; if (nfiles > header_threshhold) { - fmt = header_fmt; + fmt = header_fmt_str; } - while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) { - if (fmt) { + 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.status; + return G.exitcode; }