Does anyone need 'tac' command?

hi,

I write a ugly 'tac' applet for busybox, it's very simple, just print 
input file lines in reverse, hope it could be helpful.

diff -urN busybox-1.00-pre1/coreutils/Config.in busybox-1.00/coreutils/Config.in
--- busybox-1.00-pre1/coreutils/Config.in       2003-07-15 03:37:08.000000000 
+0800
+++ busybox-1.00/coreutils/Config.in    2003-07-30 17:33:04.000000000 +0800
@@ -421,6 +421,12 @@
        help
          sync is used to flush filesystem buffers.
 
+config CONFIG_TAC
+       bool "tac"
+       default n
+       help
+         tac is used to concatenate and print files in reverse.
+
 config CONFIG_TAIL
        bool "tail"
        default n
diff -urN busybox-1.00-pre1/coreutils/Makefile.in 
busybox-1.00/coreutils/Makefile.in
--- busybox-1.00-pre1/coreutils/Makefile.in     2003-07-15 05:20:43.000000000 
+0800
+++ busybox-1.00/coreutils/Makefile.in  2003-07-30 17:33:05.000000000 +0800
@@ -67,6 +67,7 @@
 COREUTILS-$(CONFIG_SORT)       += sort.o
 COREUTILS-$(CONFIG_STTY)               += stty.o
 COREUTILS-$(CONFIG_SYNC)       += sync.o
+COREUTILS-$(CONFIG_TAC)                += tac.o
 COREUTILS-$(CONFIG_TAIL)       += tail.o
 COREUTILS-$(CONFIG_TEE)                += tee.o
 COREUTILS-$(CONFIG_TEST)               += test.o
diff -urN busybox-1.00-pre1/coreutils/tac.c busybox-1.00/coreutils/tac.c
--- busybox-1.00-pre1/coreutils/tac.c   1970-01-01 08:00:00.000000000 +0800
+++ busybox-1.00/coreutils/tac.c        2003-07-30 17:33:05.000000000 +0800
@@ -0,0 +1,140 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * tac implementation for busybox
+ *
+ * Copyright (C) 2003  Yang Xiaopeng  <yxp@xxxxxxxxxxxxxx>
+ *
+ * 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 of the License, 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
+ *
+ */
+
+/* tac - concatenate and print files in reverse */
+
+/* Writen by Yang Xiaopeng (yxp@xxxxxxxxxxxxxx), refer to the tac 
+ * source code Written by Jay Lepreau (lepreau@xxxxxxxxxxx). */
+
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include "busybox.h"
+
+#ifndef DEFAULT_TMPDIR
+#define DEFAULT_TMPDIR "/tmp"
+#endif
+
+/* Print file to stdout in reverse */
+static int tac_file(int fd)
+{
+       struct stat stats;
+       char *map, *ptr, *end;
+
+       if (fstat(fd, &stats)) {
+               return -1;
+       }
+
+       map = mmap(0, stats.st_size, PROT_READ, MAP_SHARED, fd, 0);
+       if (map == MAP_FAILED) {
+               return -1;
+       }
+
+       ptr = end = map + stats.st_size - 1;
+       while (ptr >= map) {
+               if (*ptr == '\n') ptr--;
+               while (ptr >= map && *ptr != '\n') ptr--;
+               bb_full_write(STDOUT_FILENO, ptr+1, end-ptr);
+               end = ptr;
+       }
+       munmap(map, stats.st_size);
+       
+       return 0;
+}
+
+/* Make a copy of the standard input. */
+static int save_stdin(int fdin)
+{
+       static char *template = NULL;
+       static char *tempdir;
+       int fd;
+
+       tempdir = getenv("TMPDIR");
+       if (!tempdir)
+               tempdir = DEFAULT_TMPDIR;
+       template = xmalloc(strlen(tempdir) + 11);
+       sprintf(template, "%s/tacXXXXXX", tempdir);
+
+       fd = mkstemp(template);
+       if (fd == -1) {
+               bb_error_msg("Can't creat temp file\n");
+               return -1;
+       }
+
+       if (bb_copyfd(fdin, fd, 0) < 0) {
+               bb_error_msg("Copy file error\n");
+               return -1;
+       }
+
+       unlink(template);
+       free(template);
+
+       return fd;
+}
+
+extern int tac_main(int argc, char **argv)
+{
+       FILE *f;
+       int retval = EXIT_SUCCESS;
+       struct stat stats;
+       int fd;
+       int error;
+
+       argv++;
+       if (!*argv)
+               *--argv = "-";
+
+       do {
+               if ((f = bb_wfopen_input(*argv)) != NULL) {
+                       fd = fileno(f);
+                       if (fstat(fd, &stats)) {
+                               bb_error_msg("Can't stat input file\n");
+                               retval = EXIT_FAILURE;
+                               break;
+                       }
+
+                       if (S_ISREG(stats.st_mode)) {
+                               error = tac_file(fd);
+                       } else {
+                               fd = save_stdin(fd);
+                               if (fd == -1) {
+                                       retval = EXIT_FAILURE;
+                                       break;
+                               }
+
+                               error = tac_file(fd);
+                               close(fd);
+                       }
+
+                       bb_fclose_nonstdin(f);
+
+                       if (!error) {
+                               continue;
+                       }
+               }
+               retval = EXIT_FAILURE;
+       } while (*++argv);
+
+       return retval;
+}
diff -urN busybox-1.00-pre1/include/applets.h busybox-1.00/include/applets.h
--- busybox-1.00-pre1/include/applets.h 2003-07-05 15:51:31.000000000 +0800
+++ busybox-1.00/include/applets.h      2003-07-30 17:33:20.000000000 +0800
@@ -544,6 +544,9 @@
 #ifdef CONFIG_SYSLOGD
        APPLET(syslogd, syslogd_main, _BB_DIR_SBIN, _BB_SUID_NEVER)
 #endif
+#ifdef CONFIG_TAC
+       APPLET(tac, tac_main, _BB_DIR_BIN, _BB_SUID_NEVER)
+#endif
 #ifdef CONFIG_TAIL
        APPLET(tail, tail_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER)
 #endif
diff -urN busybox-1.00-pre1/include/usage.h busybox-1.00/include/usage.h
--- busybox-1.00-pre1/include/usage.h   2003-07-15 06:14:49.000000000 +0800
+++ busybox-1.00/include/usage.h        2003-07-30 17:33:20.000000000 +0800
@@ -2112,6 +2112,10 @@
        "$ syslogd -R masterlog:514\n" \
        "$ syslogd -R 192.168.1.1:601\n"
 
+#define tac_trivial_usage \
+       "[FILE]..."
+#define tac_full_usage \
+       "Concatenates FILE(s) and prints them to stdout in reverse.\n\n"
 
 #ifndef CONFIG_FEATURE_FANCY_TAIL
   #define USAGE_UNSIMPLE_TAIL(a)
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