1 /* $OpenBSD: look.c,v 1.27 2022/12/04 23:50:48 cheloha 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(2, "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 default: 97 usage(); 98 } 99 argc -= optind; 100 argv += optind; 101 102 switch (argc) { 103 case 2: /* Don't set -df for user. */ 104 string = *argv++; 105 file = *argv; 106 break; 107 case 1: /* But set -df by default. */ 108 dflag = fflag = 1; 109 string = *argv; 110 break; 111 default: 112 usage(); 113 } 114 115 if (termchar != '\0' && (p = strchr(string, termchar)) != NULL) 116 *++p = '\0'; 117 118 if ((fd = open(file, O_RDONLY)) == -1 || fstat(fd, &sb) == -1) 119 err(2, "%s", file); 120 if (sb.st_size > SIZE_MAX) 121 errc(2, EFBIG, "%s", file); 122 123 if (pledge("stdio", NULL) == -1) 124 err(2, "pledge"); 125 126 if ((front = mmap(NULL, 127 (size_t)sb.st_size, PROT_READ, MAP_PRIVATE, fd, (off_t)0)) == MAP_FAILED) 128 err(2, "%s", file); 129 back = front + sb.st_size; 130 exit(look(string, front, back)); 131 } 132 133 int 134 look(char *string, char *front, char *back) 135 { 136 int ch; 137 char *readp, *writep; 138 139 /* Reformat string to avoid doing it multiple times later. */ 140 for (readp = writep = string; (ch = *readp++);) { 141 if (fflag) 142 ch = tolower((unsigned char)ch); 143 if (!dflag || isalnum((unsigned char)ch)) 144 *(writep++) = ch; 145 } 146 *writep = '\0'; 147 148 front = binary_search(string, front, back); 149 front = linear_search(string, front, back); 150 151 if (front) 152 print_from(string, front, back); 153 return (front ? 0 : 1); 154 } 155 156 157 /* 158 * Binary search for "string" in memory between "front" and "back". 159 * 160 * This routine is expected to return a pointer to the start of a line at 161 * *or before* the first word matching "string". Relaxing the constraint 162 * this way simplifies the algorithm. 163 * 164 * Invariants: 165 * front points to the beginning of a line at or before the first 166 * matching string. 167 * 168 * back points to the beginning of a line at or after the first 169 * matching line. 170 * 171 * Base of the Invariants. 172 * front = NULL; 173 * back = EOF; 174 * 175 * Advancing the Invariants: 176 * 177 * p = first newline after halfway point from front to back. 178 * 179 * If the string at "p" is not greater than the string to match, 180 * p is the new front. Otherwise it is the new back. 181 * 182 * Termination: 183 * 184 * The definition of the routine allows it return at any point, 185 * since front is always at or before the line to print. 186 * 187 * In fact, it returns when the chosen "p" equals "back". This 188 * implies that there exists a string is least half as long as 189 * (back - front), which in turn implies that a linear search will 190 * be no more expensive than the cost of simply printing a string or two. 191 * 192 * Trying to continue with binary search at this point would be 193 * more trouble than it's worth. 194 */ 195 #define SKIP_PAST_NEWLINE(p, back) \ 196 while (p < back && *p++ != '\n'); 197 198 char * 199 binary_search(char *string, char *front, char *back) 200 { 201 char *p; 202 203 p = front + (back - front) / 2; 204 SKIP_PAST_NEWLINE(p, back); 205 206 /* 207 * If the file changes underneath us, make sure we don't 208 * infinitely loop. 209 */ 210 while (p < back && back > front) { 211 if (compare(string, p, back) == GREATER) 212 front = p; 213 else 214 back = p; 215 p = front + (back - front) / 2; 216 SKIP_PAST_NEWLINE(p, back); 217 } 218 return (front); 219 } 220 221 /* 222 * Find the first line that starts with string, linearly searching from front 223 * to back. 224 * 225 * Return NULL for no such line. 226 * 227 * This routine assumes: 228 * 229 * o front points at the first character in a line. 230 * o front is before or at the first line to be printed. 231 */ 232 char * 233 linear_search(char *string, char *front, char *back) 234 { 235 while (front < back) { 236 switch (compare(string, front, back)) { 237 case EQUAL: /* Found it. */ 238 return (front); 239 break; 240 case LESS: /* No such string. */ 241 return (NULL); 242 break; 243 case GREATER: /* Keep going. */ 244 break; 245 } 246 SKIP_PAST_NEWLINE(front, back); 247 } 248 return (NULL); 249 } 250 251 /* 252 * Print as many lines as match string, starting at front. 253 */ 254 void 255 print_from(char *string, char *front, char *back) 256 { 257 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 258 for (; front < back && *front != '\n'; ++front) 259 if (putchar(*front) == EOF) 260 err(2, "stdout"); 261 if (putchar('\n') == EOF) 262 err(2, "stdout"); 263 } 264 } 265 266 /* 267 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 268 * string2 (s1 ??? s2). 269 * 270 * o Matches up to len(s1) are EQUAL. 271 * o Matches up to len(s2) are GREATER. 272 * 273 * Compare understands about the -f and -d flags, and treats comparisons 274 * appropriately. 275 * 276 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 277 * "back" terminated). 278 */ 279 int 280 compare(char *s1, char *s2, char *back) 281 { 282 int ch; 283 284 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 285 ch = *s2; 286 if (fflag) 287 ch = tolower((unsigned char)ch); 288 if (dflag && !isalnum((unsigned char)ch)) { 289 ++s2; /* Ignore character in comparison. */ 290 continue; 291 } 292 if (*s1 != ch) 293 return (*s1 < ch ? LESS : GREATER); 294 } 295 return (*s1 ? GREATER : EQUAL); 296 } 297 298 void 299 usage(void) 300 { 301 (void)fprintf(stderr, 302 "usage: look [-df] [-t termchar] string [file]\n"); 303 exit(2); 304 } 305