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 38 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 39 #endif /* not lint */ 40 41 #include <sys/types.h> 42 #include <sys/stat.h> 43 #include <sys/time.h> 44 #include <sys/mman.h> 45 46 #include <limits.h> 47 #include <fcntl.h> 48 #include <errno.h> 49 #include <unistd.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include "extern.h" 54 55 static void rlines __P((FILE *, long, struct stat *)); 56 57 /* 58 * forward -- display the file, from an offset, forward. 59 * 60 * There are eight separate cases for this -- regular and non-regular 61 * files, by bytes or lines and from the beginning or end of the file. 62 * 63 * FBYTES byte offset from the beginning of the file 64 * REG seek 65 * NOREG read, counting bytes 66 * 67 * FLINES line offset from the beginning of the file 68 * REG read, counting lines 69 * NOREG read, counting lines 70 * 71 * RBYTES byte offset from the end of the file 72 * REG seek 73 * NOREG cyclically read characters into a wrap-around buffer 74 * 75 * RLINES 76 * REG mmap the file and step back until reach the correct offset. 77 * NOREG cyclically read lines into a wrap-around array of buffers 78 */ 79 void 80 forward(fp, style, off, sbp) 81 FILE *fp; 82 enum STYLE style; 83 long off; 84 struct stat *sbp; 85 { 86 register int ch; 87 struct timeval second; 88 fd_set zero; 89 90 switch(style) { 91 case FBYTES: 92 if (off == 0) 93 break; 94 if (S_ISREG(sbp->st_mode)) { 95 if (sbp->st_size < off) 96 off = sbp->st_size; 97 if (fseek(fp, off, SEEK_SET) == -1) { 98 ierr(); 99 return; 100 } 101 } else while (off--) 102 if ((ch = getc(fp)) == EOF) { 103 if (ferror(fp)) { 104 ierr(); 105 return; 106 } 107 break; 108 } 109 break; 110 case FLINES: 111 if (off == 0) 112 break; 113 for (;;) { 114 if ((ch = getc(fp)) == EOF) { 115 if (ferror(fp)) { 116 ierr(); 117 return; 118 } 119 break; 120 } 121 if (ch == '\n' && !--off) 122 break; 123 } 124 break; 125 case RBYTES: 126 if (S_ISREG(sbp->st_mode)) { 127 if (sbp->st_size >= off && 128 fseek(fp, -off, SEEK_END) == -1) { 129 ierr(); 130 return; 131 } 132 } else if (off == 0) { 133 while (getc(fp) != EOF); 134 if (ferror(fp)) { 135 ierr(); 136 return; 137 } 138 } else 139 bytes(fp, off); 140 break; 141 case RLINES: 142 if (S_ISREG(sbp->st_mode)) 143 if (!off) { 144 if (fseek(fp, 0L, SEEK_END) == -1) { 145 ierr(); 146 return; 147 } 148 } else 149 rlines(fp, off, sbp); 150 else if (off == 0) { 151 while (getc(fp) != EOF); 152 if (ferror(fp)) { 153 ierr(); 154 return; 155 } 156 } else 157 lines(fp, off); 158 break; 159 } 160 161 /* 162 * We pause for one second after displaying any data that has 163 * accumulated since we read the file. 164 */ 165 if (fflag) { 166 FD_ZERO(&zero); 167 second.tv_sec = 1; 168 second.tv_usec = 0; 169 } 170 171 for (;;) { 172 while ((ch = getc(fp)) != EOF) 173 if (putchar(ch) == EOF) 174 oerr(); 175 if (ferror(fp)) { 176 ierr(); 177 return; 178 } 179 (void)fflush(stdout); 180 if (!fflag) 181 break; 182 /* Sleep(3) is eight system calls. Do it fast. */ 183 if (select(0, &zero, &zero, &zero, &second) == -1) 184 err(1, "select: %s", strerror(errno)); 185 clearerr(fp); 186 } 187 } 188 189 /* 190 * rlines -- display the last offset lines of the file. 191 */ 192 static void 193 rlines(fp, off, sbp) 194 FILE *fp; 195 long off; 196 struct stat *sbp; 197 { 198 register off_t size; 199 register char *p; 200 char *start; 201 202 if (!(size = sbp->st_size)) 203 return; 204 205 if (size > SIZE_T_MAX) { 206 err(0, "%s: %s", fname, strerror(EFBIG)); 207 return; 208 } 209 210 if ((start = mmap(NULL, (size_t)size, 211 PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) { 212 err(0, "%s: %s", fname, strerror(EFBIG)); 213 return; 214 } 215 216 /* Last char is special, ignore whether newline or not. */ 217 for (p = start + size - 1; --size;) 218 if (*--p == '\n' && !--off) { 219 ++p; 220 break; 221 } 222 223 /* Set the file pointer to reflect the length displayed. */ 224 size = sbp->st_size - size; 225 WR(p, size); 226 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 227 ierr(); 228 return; 229 } 230 if (munmap(start, (size_t)sbp->st_size)) { 231 err(0, "%s: %s", fname, strerror(errno)); 232 return; 233 } 234 } 235