1 /* $OpenBSD: tail.c,v 1.17 2009/10/27 23:59:44 deraadt Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Edward Sze-Tyan Wang. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/types.h> 36 #include <sys/stat.h> 37 38 #include <err.h> 39 #include <errno.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <unistd.h> 44 45 #include "extern.h" 46 47 int fflag, rflag, rval; 48 char *fname; 49 int is_stdin; 50 51 static void obsolete(char **); 52 static void usage(void); 53 54 int 55 main(int argc, char *argv[]) 56 { 57 struct stat sb; 58 FILE *fp; 59 off_t off = 0; 60 enum STYLE style; 61 int ch, first; 62 char *p; 63 64 /* 65 * Tail's options are weird. First, -n10 is the same as -n-10, not 66 * -n+10. Second, the number options are 1 based and not offsets, 67 * so -n+1 is the first line, and -c-1 is the last byte. Third, the 68 * number options for the -r option specify the number of things that 69 * get displayed, not the starting point in the file. The one major 70 * incompatibility in this version as compared to historical versions 71 * is that the 'r' option couldn't be modified by the -lbc options, 72 * i.e. it was always done in lines. This version treats -rc as a 73 * number of characters in reverse order. Finally, the default for 74 * -r is the entire file, not 10 lines. 75 */ 76 #define ARG(units, forward, backward) { \ 77 if (style) \ 78 usage(); \ 79 off = strtoll(optarg, &p, 10) * (units); \ 80 if (*p) \ 81 errx(1, "illegal offset -- %s", optarg); \ 82 switch(optarg[0]) { \ 83 case '+': \ 84 if (off) \ 85 off -= (units); \ 86 style = (forward); \ 87 break; \ 88 case '-': \ 89 off = -off; \ 90 /* FALLTHROUGH */ \ 91 default: \ 92 style = (backward); \ 93 break; \ 94 } \ 95 } 96 97 obsolete(argv); 98 style = NOTSET; 99 while ((ch = getopt(argc, argv, "b:c:fn:r")) != -1) 100 switch(ch) { 101 case 'b': 102 ARG(512, FBYTES, RBYTES); 103 break; 104 case 'c': 105 ARG(1, FBYTES, RBYTES); 106 break; 107 case 'f': 108 fflag = 1; 109 break; 110 case 'n': 111 ARG(1, FLINES, RLINES); 112 break; 113 case 'r': 114 rflag = 1; 115 break; 116 case '?': 117 default: 118 usage(); 119 } 120 argc -= optind; 121 argv += optind; 122 123 if (fflag && argc > 1) 124 errx(1, "-f option only appropriate for a single file"); 125 126 /* 127 * If displaying in reverse, don't permit follow option, and convert 128 * style values. 129 */ 130 if (rflag) { 131 if (fflag) 132 usage(); 133 if (style == FBYTES) 134 style = RBYTES; 135 else if (style == FLINES) 136 style = RLINES; 137 } 138 139 /* 140 * If style not specified, the default is the whole file for -r, and 141 * the last 10 lines if not -r. 142 */ 143 if (style == NOTSET) { 144 if (rflag) { 145 off = 0; 146 style = REVERSE; 147 } else { 148 off = 10; 149 style = RLINES; 150 } 151 } 152 153 if (*argv) 154 for (first = 1; (fname = *argv++);) { 155 if ((fp = fopen(fname, "r")) == NULL || 156 fstat(fileno(fp), &sb)) { 157 ierr(); 158 continue; 159 } 160 if (argc > 1) { 161 (void)printf("%s==> %s <==\n", 162 first ? "" : "\n", fname); 163 first = 0; 164 (void)fflush(stdout); 165 } 166 167 if (rflag) 168 reverse(fp, style, off, &sb); 169 else 170 forward(fp, style, off, &sb); 171 (void)fclose(fp); 172 } 173 else { 174 fname = "stdin"; 175 is_stdin = 1; 176 177 if (fstat(fileno(stdin), &sb)) { 178 ierr(); 179 exit(1); 180 } 181 182 /* 183 * Determine if input is a pipe. 4.4BSD will set the SOCKET 184 * bit in the st_mode field for pipes. Fix this then. 185 */ 186 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 && 187 errno == ESPIPE) { 188 errno = 0; 189 fflag = 0; /* POSIX.2 requires this. */ 190 } 191 192 if (rflag) 193 reverse(stdin, style, off, &sb); 194 else 195 forward(stdin, style, off, &sb); 196 } 197 exit(rval); 198 } 199 200 /* 201 * Convert the obsolete argument form into something that getopt can handle. 202 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't 203 * the option argument for a -b, -c or -n option gets converted. 204 */ 205 static void 206 obsolete(char *argv[]) 207 { 208 char *ap, *p, *t; 209 size_t len; 210 char *start; 211 212 while ((ap = *++argv)) { 213 /* Return if "--" or not an option of any form. */ 214 if (ap[0] != '-') { 215 if (ap[0] != '+') 216 return; 217 } else if (ap[1] == '-') 218 return; 219 220 switch(*++ap) { 221 /* Old-style option. */ 222 case '0': case '1': case '2': case '3': case '4': 223 case '5': case '6': case '7': case '8': case '9': 224 225 /* Malloc space for dash, new option and argument. */ 226 len = strlen(*argv); 227 if ((start = p = malloc(len + 4)) == NULL) 228 err(1, NULL); 229 *p++ = '-'; 230 231 /* 232 * Go to the end of the option argument. Save off any 233 * trailing options (-3lf) and translate any trailing 234 * output style characters. 235 */ 236 t = *argv + len - 1; 237 if (*t == 'f' || *t == 'r') { 238 *p++ = *t; 239 *t-- = '\0'; 240 } 241 switch(*t) { 242 case 'b': 243 *p++ = 'b'; 244 *t = '\0'; 245 break; 246 case 'c': 247 *p++ = 'c'; 248 *t = '\0'; 249 break; 250 case 'l': 251 *t = '\0'; 252 /* FALLTHROUGH */ 253 case '0': case '1': case '2': case '3': case '4': 254 case '5': case '6': case '7': case '8': case '9': 255 *p++ = 'n'; 256 break; 257 default: 258 errx(1, "illegal option -- %s", *argv); 259 } 260 *p++ = *argv[0]; 261 (void)strlcpy(p, ap, start + len + 4 - p); 262 *argv = start; 263 continue; 264 265 /* 266 * Options w/ arguments, skip the argument and continue 267 * with the next option. 268 */ 269 case 'b': 270 case 'c': 271 case 'n': 272 if (!ap[1]) 273 ++argv; 274 /* FALLTHROUGH */ 275 /* Options w/o arguments, continue with the next option. */ 276 case 'f': 277 case 'r': 278 continue; 279 280 /* Illegal option, return and let getopt handle it. */ 281 default: 282 return; 283 } 284 } 285 } 286 287 static void 288 usage(void) 289 { 290 (void)fprintf(stderr, 291 "usage: tail [-f | -r] " 292 "[-b number | -c number | -n number | -number] [file ...]\n"); 293 exit(1); 294 } 295