tail.c

   1 /* vi: set sw=4 ts=4: */
   2 /* tail -- output the last part of file(s)
   3    Copyright (C) 89, 90, 91, 95, 1996 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18
  19    Original version by Paul Rubin <phr@ocf.berkeley.edu>.
  20    Extensions by David MacKenzie <djm@gnu.ai.mit.edu>.
  21    tail -f for multiple files by Ian Lance Taylor <ian@airs.com>.
  22
  23    Rewrote the option parser, removed locales support,
  24    and generally busyboxed, Erik Andersen <andersen@lineo.com>
  25
  26    Removed superfluous options and associated code ("-c", "-n", "-q").
  27    Removed "tail -f" support for multiple files.
  28    Both changes by Friedrich Vedder <fwv@myrtle.lahn.de>.
  29
  30    Compleate Rewrite to correctly support "-NUM", "+NUM", and "-s" by
  31    E.Allen Soard (esp@espsw.net).
  32
  33  */
  34 #include <sys/types.h>
  35 #include <fcntl.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <unistd.h>
  39 #include <string.h>
  40 #include <getopt.h>
  41 #include "busybox.h"
  42
  43 #define STDIN "standard input"
  44 #define LINES 0
  45 #define BYTES 1
  46
  47 static int n_files = 0;
  48 static char **files = NULL;
  49 static char * buffer;
  50 static ssize_t bytes_read=0;
  51 static ssize_t bs;
  52 static ssize_t filelocation=0;
  53 static char pip;
  54
  55 #ifdef BB_FEATURE_SIMPLE_TAIL
  56 static const char unit_type=LINES;
  57 #else
  58 static char unit_type=LINES;
  59 static char verbose = 0;
  60 #endif
  61
  62 static off_t units=0;
  63
  64 static struct suffix_mult tail_suffixes[] = {
  65         { "b", 512 },
  66         { "k", 1024 },
  67         { "m", 1048576 },
  68         { NULL, 0 }
  69 };
  70
  71 static int tail_stream(int fd)
  72 {
  73         ssize_t startpoint;
  74         ssize_t endpoint=0;
  75         ssize_t count=0;
  76         ssize_t filesize=0;
  77         int direction=1;
  78
  79         filelocation=0;
  80         startpoint=bs=BUFSIZ;
  81
  82         filesize=lseek(fd, -1, SEEK_END)+1;
  83         pip=(filesize<=0);
  84
  85         if(units>=0)
  86                 lseek(fd,0,SEEK_SET);
  87         else {
  88                 direction=-1;
  89                 count=1;
  90         }
  91         while(units != 0) {
  92                 if (pip) {
  93                         char * line;
  94                         ssize_t f_size=0;
  95
  96                         bs=BUFSIZ;
  97                         line=xmalloc(bs);
  98                         while(1) {
  99                                 bytes_read=read(fd,line,bs);
 100                                 if(bytes_read<=0)
 101                                         break;
 102                                 buffer=xrealloc(buffer,f_size+bytes_read);
 103                                 memcpy(&buffer[f_size],line,bytes_read);
 104                                 filelocation=f_size+=bytes_read;
 105                         }
 106                         bs=f_size;
 107                         if(direction<0)
 108                                 bs--;
 109                         if (line)
 110                                 free(line);
 111                 } else {
 112                         filelocation = lseek(fd, 0, SEEK_CUR);
 113                         if(direction<0) {
 114                                 if(filelocation<bs)
 115                                         bs=filelocation;
 116                                 filelocation = lseek(fd, -bs, SEEK_CUR);
 117                         }
 118                         bytes_read = read(fd, buffer, bs);
 119                         if (bytes_read <= 0)
 120                                 break;
 121                         bs=bytes_read;
 122                 }
 123                 startpoint=bs;
 124                 if(direction>0) {
 125                         endpoint=startpoint;
 126                         startpoint=0;
 127                 }
 128                 for(;startpoint!=endpoint;startpoint+=direction) {
 129 #ifndef BB_FEATURE_SIMPLE_TAIL
 130                         if(unit_type==BYTES)
 131                                 count++;
 132                         else
 133 #endif
 134                                 if(buffer[startpoint-1]=='\n')
 135                                         count++;
 136                         if (!pip)
 137                                 filelocation=lseek(fd,0,SEEK_CUR);
 138                         if(count==units*direction)
 139                                 break;
 140                 }
 141                 if((count==units*direction) | pip)
 142                         break;
 143                 if(direction<0){
 144                         filelocation = lseek(fd, -bytes_read, SEEK_CUR);
 145                         if(filelocation==0)
 146                                 break;
 147                 }
 148         }
 149         if(pip && (direction<0))
 150                 bs++;
 151         bytes_read=bs-startpoint;
 152         memcpy(&buffer[0],&buffer[startpoint],bytes_read);
 153
 154         return 0;
 155 }
 156
 157 void add_file(char *name)
 158 {
 159         ++n_files;
 160         files = xrealloc(files, n_files);
 161         files[n_files - 1] = (char *) xmalloc(strlen(name) + 1);
 162         strcpy(files[n_files - 1], name);
 163 }
 164
 165 int tail_main(int argc, char **argv)
 166 {
 167         int show_headers = 1;
 168         int test;
 169         int opt;
 170         char follow=0;
 171         int sleep_int=1;
 172         int *fd;
 173
 174         opterr = 0;
 175
 176         while ((opt=getopt(argc,argv,"c:fhn:s:q:v")) >0) {
 177
 178                 switch (opt) {
 179 #ifndef BB_FEATURE_SIMPLE_TAIL
 180                 case 'q':
 181                         show_headers = 0;
 182                         break;
 183                 case 's':
 184                         sleep_int = atoi(optarg);
 185                         if(sleep_int<1)
 186                                 sleep_int=1;
 187                         break;
 188                 case 'v':
 189                         verbose = 1;
 190                         break;
 191                 case 'c':
 192                         unit_type = BYTES;
 193                         /* FALLS THROUGH */
 194 #endif
 195                 case 'n':
 196                         test = parse_number(optarg, tail_suffixes);
 197                         if (test) {
 198                                 if (optarg[0] == '+')
 199                                         units = test;
 200                                 else
 201                                         units = -(test+1);
 202                         } else
 203                                 usage(tail_usage);
 204                         break;
 205                 case 'f':
 206                         follow = 1;
 207                         break;
 208                 default:
 209                         usage(tail_usage);
 210                 }
 211         }
 212         while (optind <= argc) {
 213                 if(optind==argc) {
 214                         if (n_files==0)
 215                                 add_file(STDIN);
 216                         else
 217                                 break;
 218                 }else {
 219                         if (!strcmp(argv[optind], "-")) {
 220                                 add_file(STDIN);
 221                         } else {
 222                                 add_file(argv[optind]);
 223                         }
 224                         optind++;
 225                 }
 226         }
 227         if(units==0)
 228                 units=-11;
 229         if(units>0)
 230                 units--;
 231         fd=xmalloc(sizeof(int)*n_files);
 232         if (n_files == 1)
 233 #ifndef BB_FEATURE_SIMPLE_TAIL
 234                 if (!verbose)
 235 #endif
 236                         show_headers = 0;
 237         buffer=xmalloc(BUFSIZ);
 238         for (test = 0; test < n_files; test++) {
 239                 if (show_headers)
 240                         printf("==> %s <==\n", files[test]);
 241                 if (!strcmp(files[test], STDIN))
 242                         fd[test] = 0;
 243                 else
 244                         fd[test] = open(files[test], O_RDONLY);
 245                 if (fd[test] == -1)
 246                         error_msg_and_die("Unable to open file %s.\n", files[test]);
 247                 tail_stream(fd[test]);
 248
 249                 bs=BUFSIZ;
 250                 while (1) {
 251                         if((filelocation>0 || pip)){
 252                                 write(1,buffer,bytes_read);
 253                         }
 254                         bytes_read = read(fd[test], buffer, bs);
 255                         filelocation+=bytes_read;
 256                         if (bytes_read <= 0) {
 257                                 break;
 258                         }
 259                         usleep(sleep_int * 1000);
 260                 }
 261                 if(n_files>1)
 262                         printf("\n");
 263         }
 264         while(1){
 265                 for (test = 0; test < n_files; test++) {
 266                         if(!follow){
 267                                 close(fd[test]);
 268                                 continue;
 269                         } else {
 270                                 sleep(sleep_int);
 271                                 bytes_read = read(fd[test], buffer, bs);
 272                                 if(bytes_read>0) {
 273                                         if (show_headers)
 274                                                 printf("==> %s <==\n", files[test]);
 275                                         write(1,buffer,bytes_read);
 276                                         if(n_files>1)
 277                                                 printf("\n");
 278                                 }
 279                         }
 280                 }
 281                 if(!follow)
 282                         break;
 283         }
 284         if (fd)
 285                 free(fd);
 286         if (buffer)
 287                 free(buffer);
 288         if(files)
 289                 free(files);
 290         return 0;
 291 }
 292
 293 /*
 294 Local Variables:
 295 c-file-style: "linux"
 296 c-basic-offset: 4
 297 tab-width: 4
 298 End:
 299 */