/* tac - concatenate and print files in reverse Copyright (C) 1988-1991, 1995-2004 Free Software Foundation, Inc. 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, 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. */ /* Written by Jay Lepreau (lepreau@cs.utah.edu). GNU enhancements by David MacKenzie (djm@gnu.ai.mit.edu). */ /* Copy each FILE, or the standard input if none are given or when a FILE name of "-" is encountered, to the standard output with the order of the records reversed. The records are separated by instances of a string, or a newline if none is given. By default, the separator string is attached to the end of the record that it follows in the file. Options: -b, --before The separator is attached to the beginning of the record that it precedes in the file. -r, --regex The separator is a regular expression. -s, --separator=separator Use SEPARATOR as the record separator. To reverse a file byte by byte, use (in bash, ksh, or sh): tac -r -s '.\| ' file */ #include #include #include #include #include "system.h" #include #include "error.h" #include "quote.h" #include "quotearg.h" #include "safe-read.h" /* The official name of this program (e.g., no `g' prefix). */ #define PROGRAM_NAME "tac" #define AUTHORS "Jay Lepreau", "David MacKenzie" #if defined __MSDOS__ || defined _WIN32 /* Define this to non-zero on systems for which the regular mechanism (of unlinking an open file and expecting to be able to write, seek back to the beginning, then reread it) doesn't work. E.g., on Windows and DOS systems. */ # define DONT_UNLINK_WHILE_OPEN 1 #endif #ifndef DEFAULT_TMPDIR # define DEFAULT_TMPDIR "/tmp" #endif /* The number of bytes per atomic read. */ #define INITIAL_READSIZE 8192 /* The number of bytes per atomic write. */ #define WRITESIZE 8192 /* The name this program was run with. */ char *program_name; /* The string that separates the records of the file. */ static char *separator; /* True if we have ever read standard input. */ static bool have_read_stdin = false; /* If true, print `separator' along with the record preceding it in the file; otherwise with the record following it. */ static bool separator_ends_record; /* 0 if `separator' is to be matched as a regular expression; otherwise, the length of `separator', used as a sentinel to stop the search. */ static size_t sentinel_length; /* The length of a match with `separator'. If `sentinel_length' is 0, `match_length' is computed every time a match succeeds; otherwise, it is simply the length of `separator'. */ static size_t match_length; /* The input buffer. */ static char *G_buffer; /* The number of bytes to read at once into `buffer'. */ static size_t read_size; /* The size of `buffer'. This is read_size * 2 + sentinel_length + 2. The extra 2 bytes allow `past_end' to have a value beyond the end of `G_buffer' and `match_start' to run off the front of `G_buffer'. */ static size_t G_buffer_size; /* The compiled regular expression representing `separator'. */ static struct re_pattern_buffer compiled_separator; static struct option const longopts[] = { {"before", no_argument, NULL, 'b'}, {"regex", no_argument, NULL, 'r'}, {"separator", required_argument, NULL, 's'}, {GETOPT_HELP_OPTION_DECL}, {GETOPT_VERSION_OPTION_DECL}, {NULL, 0, NULL, 0} }; void usage (int status) { if (status != EXIT_SUCCESS) fprintf (stderr, _("Try `%s --help' for more information.\n"), program_name); else { printf (_("\ Usage: %s [OPTION]... [FILE]...\n\ "), program_name); fputs (_("\ Write each FILE to standard output, last line first.\n\ With no FILE, or when FILE is -, read standard input.\n\ \n\ "), stdout); fputs (_("\ Mandatory arguments to long options are mandatory for short options too.\n\ "), stdout); fputs (_("\ -b, --before attach the separator before instead of after\n\ -r, --regex interpret the separator as a regular expression\n\ -s, --separator=STRING use STRING as the separator instead of newline\n\ "), stdout); fputs (HELP_OPTION_DESCRIPTION, stdout); fputs (VERSION_OPTION_DESCRIPTION, stdout); printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT); } exit (status); } /* Print the characters from START to PAST_END - 1. If START is NULL, just flush the buffer. */ static void output (const char *start, const char *past_end) { static char buffer[WRITESIZE]; static size_t bytes_in_buffer = 0; size_t bytes_to_add = past_end - start; size_t bytes_available = WRITESIZE - bytes_in_buffer; if (start == 0) { fwrite (buffer, 1, bytes_in_buffer, stdout); bytes_in_buffer = 0; return; } /* Write out as many full buffers as possible. */ while (bytes_to_add >= bytes_available) { memcpy (buffer + bytes_in_buffer, start, bytes_available); bytes_to_add -= bytes_available; start += bytes_available; fwrite (buffer, 1, WRITESIZE, stdout); bytes_in_buffer = 0; bytes_available = WRITESIZE; } memcpy (buffer + bytes_in_buffer, start, bytes_to_add); bytes_in_buffer += bytes_to_add; } /* Print in reverse the file open on descriptor FD for reading FILE. Return true if successful. */ static bool tac_seekable (int input_fd, const char *file) { /* Pointer to the location in `G_buffer' where the search for the next separator will begin. */ char *match_start; /* Pointer to one past the rightmost character in `G_buffer' that has not been printed yet. */ char *past_end; /* Length of the record growing in `G_buffer'. */ size_t saved_record_size; /* Offset in the file of the next read. */ off_t file_pos; /* True if `output' has not been called yet for any file. Only used when the separator is attached to the preceding record. */ bool first_time = true; char first_char = *separator; /* Speed optimization, non-regexp. */ char *separator1 = separator + 1; /* Speed optimization, non-regexp. */ size_t match_length1 = match_length - 1; /* Speed optimization, non-regexp. */ struct re_registers regs; /* Find the size of the input file. */ file_pos = lseek (input_fd, (off_t) 0, SEEK_END); if (file_pos < 1) return true; /* It's an empty file. */ /* Arrange for the first read to lop off enough to leave the rest of the file a multiple of `read_size'. Since `read_size' can change, this may not always hold during the program run, but since it usually will, leave it here for i/o efficiency (page/sector boundaries and all that). Note: the efficiency gain has not been verified. */ saved_record_size = file_pos % read_size; if (saved_record_size == 0) saved_record_size = read_size; file_pos -= saved_record_size; /* `file_pos' now points to the start of the last (probably partial) block in the input file. */ if (lseek (input_fd, file_pos, SEEK_SET) < 0) error (0, errno, _("%s: seek failed"), quotearg_colon (file)); if (safe_read (input_fd, G_buffer, saved_record_size) != saved_record_size) { error (0, errno, _("%s: read error"), quotearg_colon (file)); return false; } match_start = past_end = G_buffer + saved_record_size; /* For non-regexp search, move past impossible positions for a match. */ if (sentinel_length) match_start -= match_length1; for (;;) { /* Search backward from `match_start' - 1 to `G_buffer' for a match with `separator'; for speed, use strncmp if `separator' contains no metacharacters. If the match succeeds, set `match_start' to point to the start of the match and `match_length' to the length of the match. Otherwise, make `match_start' < `G_buffer'. */ if (sentinel_length == 0) { ptrdiff_t i = match_start - G_buffer; int ret; if (! (INT_MIN < i && i <= INT_MAX)) error (EXIT_FAILURE, 0, _("record too large")); ret = re_search (&compiled_separator, G_buffer, i, i - 1, -i, ®s); if (ret == -1) match_start = G_buffer - 1; else if (ret == -2) { error (EXIT_FAILURE, 0, _("error in regular expression search")); } else { match_start = G_buffer + regs.start[0]; match_length = regs.end[0] - regs.start[0]; } } else { /* `match_length' is constant for non-regexp boundaries. */ while (*--match_start != first_char || (match_length1 && strncmp (match_start + 1, separator1, match_length1))) /* Do nothing. */ ; } /* Check whether we backed off the front of `G_buffer' without finding a match for `separator'. */ if (match_start < G_buffer) { if (file_pos == 0) { /* Hit the beginning of the file; print the remaining record. */ output (G_buffer, past_end); return true; } saved_record_size = past_end - G_buffer; if (saved_record_size > read_size) { /* `G_buffer_size' is about twice `read_size', so since we want to read in another `read_size' bytes before the data already in `G_buffer', we need to increase `G_buffer_size'. */ char *newbuffer; size_t offset = sentinel_length ? sentinel_length : 1; ptrdiff_t match_start_offset = match_start - G_buffer; ptrdiff_t past_end_offset = past_end - G_buffer; size_t old_G_buffer_size = G_buffer_size; read_size *= 2; G_buffer_size = read_size * 2 + sentinel_length + 2; if (G_buffer_size < old_G_buffer_size) xalloc_die (); newbuffer = xrealloc (G_buffer - offset, G_buffer_size); newbuffer += offset; /* Adjust the pointers for the new buffer location. */ match_start = newbuffer + match_start_offset; past_end = newbuffer + past_end_offset; G_buffer = newbuffer; } /* Back up to the start of the next bufferfull of the file. */ if (file_pos >= read_size) file_pos -= read_size; else { read_size = file_pos; file_pos = 0; } if (lseek (input_fd, file_pos, SEEK_SET) < 0) error (0, errno, _("%s: seek failed"), quotearg_colon (file)); /* Shift the pending record data right to make room for the new. The source and destination regions probably overlap. */ memmove (G_buffer + read_size, G_buffer, saved_record_size); past_end = G_buffer + read_size + saved_record_size; /* For non-regexp searches, avoid unneccessary scanning. */ if (sentinel_length) match_start = G_buffer + read_size; else match_start = past_end; if (safe_read (input_fd, G_buffer, read_size) != read_size) { error (0, errno, _("%s: read error"), quotearg_colon (file)); return false; } } else { /* Found a match of `separator'. */ if (separator_ends_record) { char *match_end = match_start + match_length; /* If this match of `separator' isn't at the end of the file, print the record. */ if (!first_time || match_end != past_end) output (match_end, past_end); past_end = match_end; first_time = false; } else { output (match_start, past_end); past_end = match_start; } /* For non-regex matching, we can back up. */ if (sentinel_length > 0) match_start -= match_length - 1; } } } #if DONT_UNLINK_WHILE_OPEN static const char *file_to_remove; static FILE *fp_to_close; static void unlink_tempfile (void) { fclose (fp_to_close); unlink (file_to_remove); } static void record_or_unlink_tempfile (char const *fn, FILE *fp) { if (!file_to_remove) { file_to_remove = fn; fp_to_close = fp; atexit (unlink_tempfile); } } #else static void record_or_unlink_tempfile (char const *fn, FILE *fp ATTRIBUTE_UNUSED) { unlink (fn); } #endif /* Copy from file descriptor INPUT_FD (corresponding to the named FILE) to a temporary file, and set *G_TMP and *G_TEMPFILE to the resulting stream and file name. Return true if successful. */ static bool copy_to_temp (FILE **g_tmp, char **g_tempfile, int input_fd, char const *file) { static char *template = NULL; static char *tempdir; char *tempfile; FILE *tmp; int fd; if (template == NULL) { char const * const Template = "%s/tacXXXXXX"; tempdir = getenv ("TMPDIR"); if (tempdir == NULL) tempdir = DEFAULT_TMPDIR; /* Subtract 2 for `%s' and add 1 for the trailing NUL byte. */ template = xmalloc (strlen (tempdir) + strlen (Template) - 2 + 1); sprintf (template, Template, tempdir); } /* FIXME: there's a small window between a successful mkstemp call and the unlink that's performed by record_or_unlink_tempfile. If we're interrupted in that interval, this code fails to remove the temporary file. On systems that define DONT_UNLINK_WHILE_OPEN, the window is much larger -- it extends to the atexit-called unlink_tempfile. FIXME: clean up upon fatal signal. Don't block them, in case $TMPFILE is a remote file system. */ tempfile = template; fd = mkstemp (template); if (fd == -1) { error (0, errno, _("cannot create temporary file %s"), quote (tempfile)); return false; } tmp = fdopen (fd, "w+"); if (tmp == NULL) { error (0, errno, _("cannot open %s for writing"), quote (tempfile)); close (fd); unlink (tempfile); return false; } record_or_unlink_tempfile (tempfile, tmp); while (1) { size_t bytes_read = safe_read (input_fd, G_buffer, read_size); if (bytes_read == 0) break; if (bytes_read == SAFE_READ_ERROR) { error (0, errno, _("%s: read error"), quotearg_colon (file)); goto Fail; } if (fwrite (G_buffer, 1, bytes_read, tmp) != bytes_read) { error (0, errno, _("%s: write error"), quotearg_colon (tempfile)); goto Fail; } } if (fflush (tmp) != 0) { error (0, errno, _("%s: write error"), quotearg_colon (tempfile)); goto Fail; } SET_BINARY (fileno (tmp)); *g_tmp = tmp; *g_tempfile = tempfile; return true; Fail: fclose (tmp); return false; } /* Copy INPUT_FD to a temporary, then tac that file. Return true if successful. */ static bool tac_nonseekable (int input_fd, const char *file) { FILE *tmp_stream; char *tmp_file; copy_to_temp (&tmp_stream, &tmp_file, input_fd, file); return tac_seekable (fileno (tmp_stream), tmp_file); } /* Print FILE in reverse, copying it to a temporary file first if it is not seekable. Return true if successful. */ static bool tac_file (const char *filename) { bool ok; off_t file_size; int fd; if (STREQ (filename, "-")) { have_read_stdin = true; fd = STDIN_FILENO; filename = _("standard input"); } else { fd = open (filename, O_RDONLY); if (fd < 0) { error (0, errno, _("cannot open %s for reading"), quote (filename)); return false; } } /* We need binary I/O, since `tac' relies on `lseek' and byte counts. Binary output will leave the lines' ends (NL or CR/LF) intact when the output is a disk file. Writing a file with CR/LF pairs at end of lines in text mode has no visible effect on console output, since two CRs in a row are just like one CR. */ SET_BINARY2 (fd, STDOUT_FILENO); file_size = lseek (fd, (off_t) 0, SEEK_END); ok = (0 <= file_size ? tac_seekable (fd, filename) : tac_nonseekable (fd, filename)); if (fd != STDIN_FILENO && close (fd) == -1) { error (0, errno, _("%s: read error"), quotearg_colon (filename)); ok = false; } return ok; } #if 0 /* BUF_END points one byte past the end of the buffer to be searched. */ /* FIXME: describe */ static void tac_mem (const char *buf, size_t n_bytes, FILE *out) { const char *nl; const char *bol; if (n_bytes == 0) return; nl = memrchr (buf, buf + n_bytes, '\n'); bol = (nl == NULL ? buf : nl + 1); /* If the last line of the input file has no terminating newline, treat it as a special case. */ if (bol < buf + n_bytes) { /* Print out the line from bol to end of input. */ fwrite (bol, 1, (buf + n_bytes) - bol, out); /* Add a newline here. Otherwise, the first and second lines of output would appear to have been joined. */ fputc ('\n', out); } while ((nl = memrchr (buf, bol - 1, '\n')) != NULL) { /* Output the line (which includes a trailing newline) from NL+1 to BOL-1. */ fwrite (nl + 1, 1, bol - (nl + 1), out); bol = nl + 1; } /* If there's anything left, output the last line: BUF .. BOL-1. When the first byte of the input is a newline, there is nothing left to do here. */ if (buf < bol) fwrite (buf, 1, bol - buf, out); /* FIXME: this is work in progress.... */ } /* FIXME: describe */ static bool tac_stdin_to_mem (void) { char *buf = NULL; size_t bufsiz = 8 * BUFSIZ; size_t delta = 8 * BUFSIZ; size_t n_bytes = 0; while (1) { size_t bytes_read; char *new_buf = realloc (buf, bufsiz); if (new_buf == NULL) { /* Write contents of buf to a temporary file, ... */ /* FIXME */ /* Free the buffer and fall back on the code that relies on a temporary file. */ free (buf); /* FIXME */ abort (); } buf = new_buf; bytes_read = safe_read (STDIN_FILENO, buf + n_bytes, bufsiz - n_bytes); if (bytes_read == 0) break; if (bytes_read == SAFE_READ_ERROR) error (EXIT_FAILURE, errno, _("stdin: read error")); n_bytes += bytes_read; bufsiz += delta; } tac_mem (buf, n_bytes, stdout); return true; } #endif int main (int argc, char **argv) { const char *error_message; /* Return value from re_compile_pattern. */ int optc; bool ok; size_t half_buffer_size; /* Initializer for file_list if no file-arguments were specified on the command line. */ static char const *const default_file_list[] = {"-", NULL}; char const *const *file; initialize_main (&argc, &argv); program_name = argv[0]; setlocale (LC_ALL, ""); bindtextdomain (PACKAGE, LOCALEDIR); textdomain (PACKAGE); atexit (close_stdout); separator = "\n"; sentinel_length = 1; separator_ends_record = true; while ((optc = getopt_long (argc, argv, "brs:", longopts, NULL)) != -1) { switch (optc) { case 'b': separator_ends_record = false; break; case 'r': sentinel_length = 0; break; case 's': separator = optarg; if (*separator == 0) error (EXIT_FAILURE, 0, _("separator cannot be empty")); break; case_GETOPT_HELP_CHAR; case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS); default: usage (EXIT_FAILURE); } } if (sentinel_length == 0) { compiled_separator.allocated = 100; compiled_separator.buffer = xmalloc (compiled_separator.allocated); compiled_separator.fastmap = xmalloc (256); compiled_separator.translate = 0; error_message = re_compile_pattern (separator, strlen (separator), &compiled_separator); if (error_message) error (EXIT_FAILURE, 0, "%s", error_message); } else match_length = sentinel_length = strlen (separator); read_size = INITIAL_READSIZE; while (sentinel_length >= read_size / 2) { if (SIZE_MAX / 2 < read_size) xalloc_die (); read_size *= 2; } half_buffer_size = read_size + sentinel_length + 1; G_buffer_size = 2 * half_buffer_size; if (! (read_size < half_buffer_size && half_buffer_size < G_buffer_size)) xalloc_die (); G_buffer = xmalloc (G_buffer_size); if (sentinel_length) { strcpy (G_buffer, separator); G_buffer += sentinel_length; } else { ++G_buffer; } file = (optind < argc ? (char const *const *) &argv[optind] : default_file_list); { size_t i; ok = true; for (i = 0; file[i]; ++i) ok &= tac_file (file[i]); } /* Flush the output buffer. */ output ((char *) NULL, (char *) NULL); if (have_read_stdin && close (STDIN_FILENO) < 0) error (EXIT_FAILURE, errno, "-"); exit (ok ? EXIT_SUCCESS : EXIT_FAILURE); }