tail.c revision 1590
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 "extern.h" 55 56int fflag, rflag, rval; 57char *fname; 58 59static void obsolete __P((char **)); 60static void usage __P((void)); 61 62int 63main(argc, argv) 64 int argc; 65 char *argv[]; 66{ 67 struct stat sb; 68 FILE *fp; 69 long off; 70 enum STYLE style; 71 int ch, first; 72 char *p; 73 74 /* 75 * Tail's options are weird. First, -n10 is the same as -n-10, not 76 * -n+10. Second, the number options are 1 based and not offsets, 77 * so -n+1 is the first line, and -c-1 is the last byte. Third, the 78 * number options for the -r option specify the number of things that 79 * get displayed, not the starting point in the file. The one major 80 * incompatibility in this version as compared to historical versions 81 * is that the 'r' option couldn't be modified by the -lbc options, 82 * i.e. it was always done in lines. This version treats -rc as a 83 * number of characters in reverse order. Finally, the default for 84 * -r is the entire file, not 10 lines. 85 */ 86#define ARG(units, forward, backward) { \ 87 if (style) \ 88 usage(); \ 89 off = strtol(optarg, &p, 10) * (units); \ 90 if (*p) \ 91 err(1, "illegal offset -- %s", optarg); \ 92 switch(optarg[0]) { \ 93 case '+': \ 94 if (off) \ 95 off -= (units); \ 96 style = (forward); \ 97 break; \ 98 case '-': \ 99 off = -off; \ 100 /* FALLTHROUGH */ \ 101 default: \ 102 style = (backward); \ 103 break; \ 104 } \ 105} 106 107 obsolete(argv); 108 style = NOTSET; 109 while ((ch = getopt(argc, argv, "b:c:fn:r")) != EOF) 110 switch(ch) { 111 case 'b': 112 ARG(512, FBYTES, RBYTES); 113 break; 114 case 'c': 115 ARG(1, FBYTES, RBYTES); 116 break; 117 case 'f': 118 fflag = 1; 119 break; 120 case 'n': 121 ARG(1, FLINES, RLINES); 122 break; 123 case 'r': 124 rflag = 1; 125 break; 126 case '?': 127 default: 128 usage(); 129 } 130 argc -= optind; 131 argv += optind; 132 133 if (fflag && argc > 1) 134 err(1, "-f option only appropriate for a single file"); 135 136 /* 137 * If displaying in reverse, don't permit follow option, and convert 138 * style values. 139 */ 140 if (rflag) { 141 if (fflag) 142 usage(); 143 if (style == FBYTES) 144 style = RBYTES; 145 else if (style == FLINES) 146 style = RLINES; 147 } 148 149 /* 150 * If style not specified, the default is the whole file for -r, and 151 * the last 10 lines if not -r. 152 */ 153 if (style == NOTSET) 154 if (rflag) { 155 off = 0; 156 style = REVERSE; 157 } else { 158 off = 10; 159 style = RLINES; 160 } 161 162 if (*argv) 163 for (first = 1; fname = *argv++;) { 164 if ((fp = fopen(fname, "r")) == NULL || 165 fstat(fileno(fp), &sb)) { 166 ierr(); 167 continue; 168 } 169 if (argc > 1) { 170 (void)printf("%s==> %s <==\n", 171 first ? "" : "\n", fname); 172 first = 0; 173 (void)fflush(stdout); 174 } 175 176 if (rflag) 177 reverse(fp, style, off, &sb); 178 else 179 forward(fp, style, off, &sb); 180 (void)fclose(fp); 181 } 182 else { 183 fname = "stdin"; 184 185 if (fstat(fileno(stdin), &sb)) { 186 ierr(); 187 exit(1); 188 } 189 190 /* 191 * Determine if input is a pipe. 4.4BSD will set the SOCKET 192 * bit in the st_mode field for pipes. Fix this then. 193 */ 194 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 && 195 errno == ESPIPE) { 196 errno = 0; 197 fflag = 0; /* POSIX.2 requires this. */ 198 } 199 200 if (rflag) 201 reverse(stdin, style, off, &sb); 202 else 203 forward(stdin, style, off, &sb); 204 } 205 exit(rval); 206} 207 208/* 209 * Convert the obsolete argument form into something that getopt can handle. 210 * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't 211 * the option argument for a -b, -c or -n option gets converted. 212 */ 213static void 214obsolete(argv) 215 char *argv[]; 216{ 217 register char *ap, *p, *t; 218 int len; 219 char *start; 220 221 while (ap = *++argv) { 222 /* Return if "--" or not an option of any form. */ 223 if (ap[0] != '-') { 224 if (ap[0] != '+') 225 return; 226 } else if (ap[1] == '-') 227 return; 228 229 switch(*++ap) { 230 /* Old-style option. */ 231 case '0': case '1': case '2': case '3': case '4': 232 case '5': case '6': case '7': case '8': case '9': 233 234 /* Malloc space for dash, new option and argument. */ 235 len = strlen(*argv); 236 if ((start = p = malloc(len + 3)) == NULL) 237 err(1, "%s", strerror(errno)); 238 *p++ = '-'; 239 240 /* 241 * Go to the end of the option argument. Save off any 242 * trailing options (-3lf) and translate any trailing 243 * output style characters. 244 */ 245 t = *argv + len - 1; 246 if (*t == 'f' || *t == 'r') { 247 *p++ = *t; 248 *t-- = '\0'; 249 } 250 switch(*t) { 251 case 'b': 252 *p++ = 'b'; 253 *t = '\0'; 254 break; 255 case 'c': 256 *p++ = 'c'; 257 *t = '\0'; 258 break; 259 case 'l': 260 *t = '\0'; 261 /* FALLTHROUGH */ 262 case '0': case '1': case '2': case '3': case '4': 263 case '5': case '6': case '7': case '8': case '9': 264 *p++ = 'n'; 265 break; 266 default: 267 err(1, "illegal option -- %s", *argv); 268 } 269 *p++ = *argv[0]; 270 (void)strcpy(p, ap); 271 *argv = start; 272 continue; 273 274 /* 275 * Options w/ arguments, skip the argument and continue 276 * with the next option. 277 */ 278 case 'b': 279 case 'c': 280 case 'n': 281 if (!ap[1]) 282 ++argv; 283 /* FALLTHROUGH */ 284 /* Options w/o arguments, continue with the next option. */ 285 case 'f': 286 case 'r': 287 continue; 288 289 /* Illegal option, return and let getopt handle it. */ 290 default: 291 return; 292 } 293 } 294} 295 296static void 297usage() 298{ 299 (void)fprintf(stderr, 300 "usage: tail [-f | -r] [-b # | -c # | -n #] [file ...]\n"); 301 exit(1); 302} 303