tail.c revision 35081
1/*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Edward Sze-Tyan Wang. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37#ifndef lint 38static char copyright[] = 39"@(#) Copyright (c) 1991, 1993\n\ 40 The Regents of the University of California. All rights reserved.\n"; 41#endif /* not lint */ 42 43#ifndef lint 44static char sccsid[] = "@(#)tail.c 8.1 (Berkeley) 6/6/93"; 45#endif /* not lint */ 46 47#include <sys/types.h> 48#include <sys/stat.h> 49#include <errno.h> 50#include <unistd.h> 51#include <stdio.h> 52#include <stdlib.h> 53#include <string.h> 54#include <err.h> 55#include "extern.h" 56 57int Fflag, fflag, rflag, rval; 58char *fname; 59 60static void obsolete __P((char **)); 61static void usage __P((void)); 62 63int 64main(argc, argv) 65 int argc; 66 char *argv[]; 67{ 68 struct stat sb; 69 FILE *fp; 70 long off; 71 enum STYLE style; 72 int ch, first; 73 char *p; 74 75 /* 76 * Tail's options are weird. First, -n10 is the same as -n-10, not 77 * -n+10. Second, the number options are 1 based and not offsets, 78 * so -n+1 is the first line, and -c-1 is the last byte. Third, the 79 * number options for the -r option specify the number of things that 80 * get displayed, not the starting point in the file. The one major 81 * incompatibility in this version as compared to historical versions 82 * is that the 'r' option couldn't be modified by the -lbc options, 83 * i.e. it was always done in lines. This version treats -rc as a 84 * number of characters in reverse order. Finally, the default for 85 * -r is the entire file, not 10 lines. 86 */ 87#define ARG(units, forward, backward) { \ 88 if (style) \ 89 usage(); \ 90 off = strtol(optarg, &p, 10) * (units); \ 91 if (*p) \ 92 errx(1, "illegal offset -- %s", optarg); \ 93 switch(optarg[0]) { \ 94 case '+': \ 95 if (off) \ 96 off -= (units); \ 97 style = (forward); \ 98 break; \ 99 case '-': \ 100 off = -off; \ 101 /* FALLTHROUGH */ \ 102 default: \ 103 style = (backward); \ 104 break; \ 105 } \ 106} 107 108 obsolete(argv); 109 style = NOTSET; 110 while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1) 111 switch(ch) { 112 case 'F': /* -F is superset of (and implies) -f */ 113 Fflag = fflag = 1; 114 break; 115 case 'b': 116 ARG(512, FBYTES, RBYTES); 117 break; 118 case 'c': 119 ARG(1, FBYTES, RBYTES); 120 break; 121 case 'f': 122 fflag = 1; 123 break; 124 case 'n': 125 ARG(1, FLINES, RLINES); 126 break; 127 case 'r': 128 rflag = 1; 129 break; 130 case '?': 131 default: 132 usage(); 133 } 134 argc -= optind; 135 argv += optind; 136 137 if (fflag && argc > 1) 138 errx(1, "-f option only appropriate for a single file"); 139 140 /* 141 * If displaying in reverse, don't permit follow option, and convert 142 * style values. 143 */ 144 if (rflag) { 145 if (fflag) 146 usage(); 147 if (style == FBYTES) 148 style = RBYTES; 149 else if (style == FLINES) 150 style = RLINES; 151 } 152 153 /* 154 * If style not specified, the default is the whole file for -r, and 155 * the last 10 lines if not -r. 156 */ 157 if (style == NOTSET) 158 if (rflag) { 159 off = 0; 160 style = REVERSE; 161 } else { 162 off = 10; 163 style = RLINES; 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"; 188 189 if (fstat(fileno(stdin), &sb)) { 190 ierr(); 191 exit(1); 192 } 193 194 /* 195 * Determine if input is a pipe. 4.4BSD will set the SOCKET 196 * bit in the st_mode field for pipes. Fix this then. 197 */ 198 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 && 199 errno == ESPIPE) { 200 errno = 0; 201 fflag = 0; /* POSIX.2 requires this. */ 202 } 203 204 if (rflag) 205 reverse(stdin, style, off, &sb); 206 else 207 forward(stdin, style, off, &sb); 208 } 209 exit(rval); 210} 211 212/* 213 * Convert the obsolete argument form into something that getopt can handle. 214 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't 215 * the option argument for a -b, -c or -n option gets converted. 216 */ 217static void 218obsolete(argv) 219 char *argv[]; 220{ 221 register char *ap, *p, *t; 222 int 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 + 3)) == NULL) 241 err(1, "malloc"); 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)strcpy(p, ap); 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 300static void 301usage() 302{ 303 (void)fprintf(stderr, 304 "usage: tail [-f | -r] [-b # | -c # | -n #] [file ...]\n"); 305 exit(1); 306} 307