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Diffstat (limited to 'coreutils/tail.c')
| -rw-r--r-- | coreutils/tail.c | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/coreutils/tail.c b/coreutils/tail.c new file mode 100644 index 0000000..2505fc3 --- /dev/null +++ b/coreutils/tail.c @@ -0,0 +1,284 @@ +/* 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][1]); + argv++; + argc--; + } +#endif + + USE_FEATURE_FANCY_TAIL(opt_complementary = "s+";) /* -s N */ + opt = getopt32(argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"), + &str_c, &str_n USE_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; +} |