1 /* $OpenBSD: tail.c,v 1.13 2006/03/22 19:43:29 kjell 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 #ifndef lint 36 static char copyright[] = 37 "@(#) Copyright (c) 1991, 1993\n\ 38 The Regents of the University of California. All rights reserved.\n"; 39 #endif /* not lint */ 40 41 #ifndef lint 42 #if 0 43 static char sccsid[] = "@(#)tail.c 8.1 (Berkeley) 6/6/93"; 44 #endif 45 static char rcsid[] = "$OpenBSD: tail.c,v 1.13 2006/03/22 19:43:29 kjell Exp $"; 46 #endif /* not lint */ 47 48 #include <sys/types.h> 49 #include <sys/stat.h> 50 51 #include <err.h> 52 #include <errno.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <unistd.h> 57 58 #include "extern.h" 59 60 int fflag, rflag, rval; 61 char *fname; 62 int is_stdin; 63 64 static void obsolete(char **); 65 static void usage(void); 66 67 int 68 main(int argc, char *argv[]) 69 { 70 struct stat sb; 71 FILE *fp; 72 off_t off = 0; 73 enum STYLE style; 74 int ch, first; 75 char *p; 76 77 /* 78 * Tail's options are weird. First, -n10 is the same as -n-10, not 79 * -n+10. Second, the number options are 1 based and not offsets, 80 * so -n+1 is the first line, and -c-1 is the last byte. Third, the 81 * number options for the -r option specify the number of things that 82 * get displayed, not the starting point in the file. The one major 83 * incompatibility in this version as compared to historical versions 84 * is that the 'r' option couldn't be modified by the -lbc options, 85 * i.e. it was always done in lines. This version treats -rc as a 86 * number of characters in reverse order. Finally, the default for 87 * -r is the entire file, not 10 lines. 88 */ 89 #define ARG(units, forward, backward) { \ 90 if (style) \ 91 usage(); \ 92 off = strtoll(optarg, &p, 10) * (units); \ 93 if (*p) \ 94 errx(1, "illegal offset -- %s", optarg); \ 95 switch(optarg[0]) { \ 96 case '+': \ 97 if (off) \ 98 off -= (units); \ 99 style = (forward); \ 100 break; \ 101 case '-': \ 102 off = -off; \ 103 /* FALLTHROUGH */ \ 104 default: \ 105 style = (backward); \ 106 break; \ 107 } \ 108 } 109 110 obsolete(argv); 111 style = NOTSET; 112 while ((ch = getopt(argc, argv, "b:c:fn:r")) != -1) 113 switch(ch) { 114 case 'b': 115 ARG(512, FBYTES, RBYTES); 116 break; 117 case 'c': 118 ARG(1, FBYTES, RBYTES); 119 break; 120 case 'f': 121 fflag = 1; 122 break; 123 case 'n': 124 ARG(1, FLINES, RLINES); 125 break; 126 case 'r': 127 rflag = 1; 128 break; 129 case '?': 130 default: 131 usage(); 132 } 133 argc -= optind; 134 argv += optind; 135 136 if (fflag && argc > 1) 137 errx(1, "-f option only appropriate for a single file"); 138 139 /* 140 * If displaying in reverse, don't permit follow option, and convert 141 * style values. 142 */ 143 if (rflag) { 144 if (fflag) 145 usage(); 146 if (style == FBYTES) 147 style = RBYTES; 148 else if (style == FLINES) 149 style = RLINES; 150 } 151 152 /* 153 * If style not specified, the default is the whole file for -r, and 154 * the last 10 lines if not -r. 155 */ 156 if (style == NOTSET) { 157 if (rflag) { 158 off = 0; 159 style = REVERSE; 160 } else { 161 off = 10; 162 style = RLINES; 163 } 164 } 165 166 if (*argv) 167 for (first = 1; (fname = *argv++);) { 168 if ((fp = fopen(fname, "r")) == NULL || 169 fstat(fileno(fp), &sb)) { 170 ierr(); 171 continue; 172 } 173 if (argc > 1) { 174 (void)printf("%s==> %s <==\n", 175 first ? "" : "\n", fname); 176 first = 0; 177 (void)fflush(stdout); 178 } 179 180 if (rflag) 181 reverse(fp, style, off, &sb); 182 else 183 forward(fp, style, off, &sb); 184 (void)fclose(fp); 185 } 186 else { 187 fname = "stdin"; 188 is_stdin = 1; 189 190 if (fstat(fileno(stdin), &sb)) { 191 ierr(); 192 exit(1); 193 } 194 195 /* 196 * Determine if input is a pipe. 4.4BSD will set the SOCKET 197 * bit in the st_mode field for pipes. Fix this then. 198 */ 199 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 && 200 errno == ESPIPE) { 201 errno = 0; 202 fflag = 0; /* POSIX.2 requires this. */ 203 } 204 205 if (rflag) 206 reverse(stdin, style, off, &sb); 207 else 208 forward(stdin, style, off, &sb); 209 } 210 exit(rval); 211 } 212 213 /* 214 * Convert the obsolete argument form into something that getopt can handle. 215 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't 216 * the option argument for a -b, -c or -n option gets converted. 217 */ 218 static void 219 obsolete(char *argv[]) 220 { 221 char *ap, *p, *t; 222 size_t len; 223 char *start; 224 225 while ((ap = *++argv)) { 226 /* Return if "--" or not an option of any form. */ 227 if (ap[0] != '-') { 228 if (ap[0] != '+') 229 return; 230 } else if (ap[1] == '-') 231 return; 232 233 switch(*++ap) { 234 /* Old-style option. */ 235 case '0': case '1': case '2': case '3': case '4': 236 case '5': case '6': case '7': case '8': case '9': 237 238 /* Malloc space for dash, new option and argument. */ 239 len = strlen(*argv); 240 if ((start = p = malloc(len + 4)) == NULL) 241 err(1, NULL); 242 *p++ = '-'; 243 244 /* 245 * Go to the end of the option argument. Save off any 246 * trailing options (-3lf) and translate any trailing 247 * output style characters. 248 */ 249 t = *argv + len - 1; 250 if (*t == 'f' || *t == 'r') { 251 *p++ = *t; 252 *t-- = '\0'; 253 } 254 switch(*t) { 255 case 'b': 256 *p++ = 'b'; 257 *t = '\0'; 258 break; 259 case 'c': 260 *p++ = 'c'; 261 *t = '\0'; 262 break; 263 case 'l': 264 *t = '\0'; 265 /* FALLTHROUGH */ 266 case '0': case '1': case '2': case '3': case '4': 267 case '5': case '6': case '7': case '8': case '9': 268 *p++ = 'n'; 269 break; 270 default: 271 errx(1, "illegal option -- %s", *argv); 272 } 273 *p++ = *argv[0]; 274 (void)strlcpy(p, ap, start + len + 4 - p); 275 *argv = start; 276 continue; 277 278 /* 279 * Options w/ arguments, skip the argument and continue 280 * with the next option. 281 */ 282 case 'b': 283 case 'c': 284 case 'n': 285 if (!ap[1]) 286 ++argv; 287 /* FALLTHROUGH */ 288 /* Options w/o arguments, continue with the next option. */ 289 case 'f': 290 case 'r': 291 continue; 292 293 /* Illegal option, return and let getopt handle it. */ 294 default: 295 return; 296 } 297 } 298 } 299 300 static void 301 usage(void) 302 { 303 (void)fprintf(stderr, 304 "usage: tail [-f | -r] [-b # | -c # | -n #] [file ...]\n"); 305 exit(1); 306 } 307