1 /* $OpenBSD: look.c,v 1.19 2016/09/13 15:27:47 millert Exp $ */ 2 /* $NetBSD: look.c,v 1.7 1995/08/31 22:41:02 jtc Exp $ */ 3 4 /*- 5 * Copyright (c) 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * David Hitz of Auspex Systems, Inc. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 /* 37 * look -- find lines in a sorted list. 38 * 39 * The man page said that TABs and SPACEs participate in -d comparisons. 40 * In fact, they were ignored. This implements historic practice, not 41 * the manual page. 42 */ 43 44 #include <sys/types.h> 45 #include <sys/mman.h> 46 #include <sys/stat.h> 47 48 #include <ctype.h> 49 #include <errno.h> 50 #include <fcntl.h> 51 #include <stdint.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <string.h> 55 #include <unistd.h> 56 #include <err.h> 57 58 #include "pathnames.h" 59 60 #define EQUAL 0 61 #define GREATER 1 62 #define LESS (-1) 63 64 int dflag, fflag; 65 66 char *binary_search(char *, char *, char *); 67 int compare(char *, char *, char *); 68 char *linear_search(char *, char *, char *); 69 int look(char *, char *, char *); 70 void print_from(char *, char *, char *); 71 void usage(void); 72 73 int 74 main(int argc, char *argv[]) 75 { 76 struct stat sb; 77 int ch, fd, termchar; 78 char *back, *file, *front, *string, *p; 79 80 if (pledge("stdio rpath", NULL) == -1) 81 err(1, "pledge"); 82 83 file = _PATH_WORDS; 84 termchar = '\0'; 85 while ((ch = getopt(argc, argv, "dft:")) != -1) 86 switch(ch) { 87 case 'd': 88 dflag = 1; 89 break; 90 case 'f': 91 fflag = 1; 92 break; 93 case 't': 94 termchar = *optarg; 95 break; 96 case '?': 97 default: 98 usage(); 99 } 100 argc -= optind; 101 argv += optind; 102 103 switch (argc) { 104 case 2: /* Don't set -df for user. */ 105 string = *argv++; 106 file = *argv; 107 break; 108 case 1: /* But set -df by default. */ 109 dflag = fflag = 1; 110 string = *argv; 111 break; 112 default: 113 usage(); 114 } 115 116 if (termchar != '\0' && (p = strchr(string, termchar)) != NULL) 117 *++p = '\0'; 118 119 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb)) 120 err(2, "%s", file); 121 if (sb.st_size > SIZE_MAX) 122 errc(2, EFBIG, "%s", file); 123 if ((front = mmap(NULL, 124 (size_t)sb.st_size, PROT_READ, MAP_PRIVATE, fd, (off_t)0)) == MAP_FAILED) 125 err(2, "%s", file); 126 back = front + sb.st_size; 127 exit(look(string, front, back)); 128 } 129 130 int 131 look(char *string, char *front, char *back) 132 { 133 int ch; 134 char *readp, *writep; 135 136 /* Reformat string to avoid doing it multiple times later. */ 137 for (readp = writep = string; ch = *readp++;) { 138 if (fflag) 139 ch = tolower((unsigned char)ch); 140 if (!dflag || isalnum((unsigned char)ch)) 141 *(writep++) = ch; 142 } 143 *writep = '\0'; 144 145 front = binary_search(string, front, back); 146 front = linear_search(string, front, back); 147 148 if (front) 149 print_from(string, front, back); 150 return (front ? 0 : 1); 151 } 152 153 154 /* 155 * Binary search for "string" in memory between "front" and "back". 156 * 157 * This routine is expected to return a pointer to the start of a line at 158 * *or before* the first word matching "string". Relaxing the constraint 159 * this way simplifies the algorithm. 160 * 161 * Invariants: 162 * front points to the beginning of a line at or before the first 163 * matching string. 164 * 165 * back points to the beginning of a line at or after the first 166 * matching line. 167 * 168 * Base of the Invariants. 169 * front = NULL; 170 * back = EOF; 171 * 172 * Advancing the Invariants: 173 * 174 * p = first newline after halfway point from front to back. 175 * 176 * If the string at "p" is not greater than the string to match, 177 * p is the new front. Otherwise it is the new back. 178 * 179 * Termination: 180 * 181 * The definition of the routine allows it return at any point, 182 * since front is always at or before the line to print. 183 * 184 * In fact, it returns when the chosen "p" equals "back". This 185 * implies that there exists a string is least half as long as 186 * (back - front), which in turn implies that a linear search will 187 * be no more expensive than the cost of simply printing a string or two. 188 * 189 * Trying to continue with binary search at this point would be 190 * more trouble than it's worth. 191 */ 192 #define SKIP_PAST_NEWLINE(p, back) \ 193 while (p < back && *p++ != '\n'); 194 195 char * 196 binary_search(char *string, char *front, char *back) 197 { 198 char *p; 199 200 p = front + (back - front) / 2; 201 SKIP_PAST_NEWLINE(p, back); 202 203 /* 204 * If the file changes underneath us, make sure we don't 205 * infinitely loop. 206 */ 207 while (p < back && back > front) { 208 if (compare(string, p, back) == GREATER) 209 front = p; 210 else 211 back = p; 212 p = front + (back - front) / 2; 213 SKIP_PAST_NEWLINE(p, back); 214 } 215 return (front); 216 } 217 218 /* 219 * Find the first line that starts with string, linearly searching from front 220 * to back. 221 * 222 * Return NULL for no such line. 223 * 224 * This routine assumes: 225 * 226 * o front points at the first character in a line. 227 * o front is before or at the first line to be printed. 228 */ 229 char * 230 linear_search(char *string, char *front, char *back) 231 { 232 while (front < back) { 233 switch (compare(string, front, back)) { 234 case EQUAL: /* Found it. */ 235 return (front); 236 break; 237 case LESS: /* No such string. */ 238 return (NULL); 239 break; 240 case GREATER: /* Keep going. */ 241 break; 242 } 243 SKIP_PAST_NEWLINE(front, back); 244 } 245 return (NULL); 246 } 247 248 /* 249 * Print as many lines as match string, starting at front. 250 */ 251 void 252 print_from(char *string, char *front, char *back) 253 { 254 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 255 for (; front < back && *front != '\n'; ++front) 256 if (putchar(*front) == EOF) 257 err(2, "stdout"); 258 if (putchar('\n') == EOF) 259 err(2, "stdout"); 260 } 261 } 262 263 /* 264 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 265 * string2 (s1 ??? s2). 266 * 267 * o Matches up to len(s1) are EQUAL. 268 * o Matches up to len(s2) are GREATER. 269 * 270 * Compare understands about the -f and -d flags, and treats comparisons 271 * appropriately. 272 * 273 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 274 * "back" terminated). 275 */ 276 int 277 compare(char *s1, char *s2, char *back) 278 { 279 int ch; 280 281 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 282 ch = *s2; 283 if (fflag) 284 ch = tolower((unsigned char)ch); 285 if (dflag && !isalnum((unsigned char)ch)) { 286 ++s2; /* Ignore character in comparison. */ 287 continue; 288 } 289 if (*s1 != ch) 290 return (*s1 < ch ? LESS : GREATER); 291 } 292 return (*s1 ? GREATER : EQUAL); 293 } 294 295 void 296 usage(void) 297 { 298 (void)fprintf(stderr, 299 "usage: look [-df] [-t termchar] string [file]\n"); 300 exit(2); 301 } 302