freebsd-dev/usr.bin/look/look.c

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/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* David Hitz of Auspex Systems, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
static const char copyright[] =
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"@(#) Copyright (c) 1991, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
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static char sccsid[] = "@(#)look.c 8.2 (Berkeley) 5/4/95";
#endif
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#endif /* not lint */
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#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
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/*
* look -- find lines in a sorted list.
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*
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* The man page said that TABs and SPACEs participate in -d comparisons.
* In fact, they were ignored. This implements historic practice, not
* the manual page.
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
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#include <ctype.h>
#include <err.h>
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#include <errno.h>
#include <fcntl.h>
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#include <limits.h>
#include <locale.h>
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
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#include <unistd.h>
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#include "pathnames.h"
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static char _path_words[] = _PATH_WORDS;
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/*
* FOLD and DICT convert characters to a normal form for comparison,
* according to the user specified flags.
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*
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* DICT expects integers because it uses a non-character value to
* indicate a character which should not participate in comparisons.
*/
#define EQUAL 0
#define GREATER 1
#define LESS (-1)
#define NO_COMPARE (-2)
#define FOLD(c) (isupper(c) ? tolower(c) : (unsigned char) (c))
#define DICT(c) (isalnum(c) ? (c) & 0xFF /* int */ : NO_COMPARE)
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int dflag, fflag;
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char *binary_search(unsigned char *, unsigned char *, unsigned char *);
int compare(unsigned char *, unsigned char *, unsigned char *);
char *linear_search(unsigned char *, unsigned char *, unsigned char *);
int look(unsigned char *, unsigned char *, unsigned char *);
void print_from(unsigned char *, unsigned char *, unsigned char *);
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static void usage(void);
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int
main(int argc, char *argv[])
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{
struct stat sb;
int ch, fd, termchar, match;
unsigned char *back, *front, *string, *p;
unsigned const char *file;
(void) setlocale(LC_CTYPE, "");
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file = _path_words;
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termchar = '\0';
while ((ch = getopt(argc, argv, "dft:")) != -1)
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switch(ch) {
case 'd':
dflag = 1;
break;
case 'f':
fflag = 1;
break;
case 't':
termchar = *optarg;
break;
case '?':
default:
usage();
}
argc -= optind;
argv += optind;
if (argc == 0)
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usage();
if (argc == 1) /* But set -df by default. */
dflag = fflag = 1;
string = *argv++;
if (argc >= 2)
file = *argv++;
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if (termchar != '\0' && (p = strchr(string, termchar)) != NULL)
*++p = '\0';
match = 1;
do {
if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb))
err(2, "%s", file);
if (sb.st_size > SIZE_T_MAX)
errx(2, "%s: %s", file, strerror(EFBIG));
if ((front = mmap(NULL, (size_t)sb.st_size, PROT_READ, MAP_SHARED, fd, (off_t)0)) == MAP_FAILED)
err(2, "%s", file);
back = front + sb.st_size;
match *= (look(string, front, back));
close(fd);
} while (argc-- > 2 && (file = *argv++));
exit(match);
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}
int
look(unsigned char *string, unsigned char *front, unsigned char *back)
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{
int ch;
unsigned char *readp, *writep;
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/* Reformat string string to avoid doing it multiple times later. */
for (readp = writep = string; (ch = *readp++);) {
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if (fflag)
ch = FOLD(ch);
if (dflag)
ch = DICT(ch);
if (ch != NO_COMPARE)
*(writep++) = ch;
}
*writep = '\0';
front = binary_search(string, front, back);
front = linear_search(string, front, back);
if (front)
print_from(string, front, back);
return (front ? 0 : 1);
}
/*
* Binary search for "string" in memory between "front" and "back".
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*
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* This routine is expected to return a pointer to the start of a line at
* *or before* the first word matching "string". Relaxing the constraint
* this way simplifies the algorithm.
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*
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* Invariants:
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* front points to the beginning of a line at or before the first
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* matching string.
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*
* back points to the beginning of a line at or after the first
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* matching line.
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*
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* Base of the Invariants.
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* front = NULL;
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* back = EOF;
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*
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* Advancing the Invariants:
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*
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* p = first newline after halfway point from front to back.
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*
* If the string at "p" is not greater than the string to match,
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* p is the new front. Otherwise it is the new back.
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*
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* Termination:
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*
* The definition of the routine allows it return at any point,
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* since front is always at or before the line to print.
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*
* In fact, it returns when the chosen "p" equals "back". This
* implies that there exists a string is least half as long as
* (back - front), which in turn implies that a linear search will
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* be no more expensive than the cost of simply printing a string or two.
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*
* Trying to continue with binary search at this point would be
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* more trouble than it's worth.
*/
#define SKIP_PAST_NEWLINE(p, back) \
while (p < back && *p++ != '\n');
char *
binary_search(unsigned char *string, unsigned char *front, unsigned char *back)
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{
unsigned char *p;
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p = front + (back - front) / 2;
SKIP_PAST_NEWLINE(p, back);
/*
* If the file changes underneath us, make sure we don't
* infinitely loop.
*/
while (p < back && back > front) {
if (compare(string, p, back) == GREATER)
front = p;
else
back = p;
p = front + (back - front) / 2;
SKIP_PAST_NEWLINE(p, back);
}
return (front);
}
/*
* Find the first line that starts with string, linearly searching from front
* to back.
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*
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* Return NULL for no such line.
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*
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* This routine assumes:
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*
* o front points at the first character in a line.
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* o front is before or at the first line to be printed.
*/
char *
linear_search(unsigned char *string, unsigned char *front, unsigned char *back)
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{
while (front < back) {
switch (compare(string, front, back)) {
case EQUAL: /* Found it. */
return (front);
break;
case LESS: /* No such string. */
return (NULL);
break;
case GREATER: /* Keep going. */
break;
}
SKIP_PAST_NEWLINE(front, back);
}
return (NULL);
}
/*
* Print as many lines as match string, starting at front.
*/
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void
print_from(unsigned char *string, unsigned char *front, unsigned char *back)
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{
for (; front < back && compare(string, front, back) == EQUAL; ++front) {
for (; front < back && *front != '\n'; ++front)
if (putchar(*front) == EOF)
err(2, "stdout");
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if (putchar('\n') == EOF)
err(2, "stdout");
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}
}
/*
* Return LESS, GREATER, or EQUAL depending on how the string1 compares with
* string2 (s1 ??? s2).
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*
* o Matches up to len(s1) are EQUAL.
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* o Matches up to len(s2) are GREATER.
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*
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* Compare understands about the -f and -d flags, and treats comparisons
* appropriately.
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*
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* The string "s1" is null terminated. The string s2 is '\n' terminated (or
* "back" terminated).
*/
int
compare(unsigned char *s1, unsigned char *s2, unsigned char *back)
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{
int ch;
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for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) {
ch = *s2;
if (fflag)
ch = FOLD(ch);
if (dflag)
ch = DICT(ch);
if (ch == NO_COMPARE) {
++s2; /* Ignore character in comparison. */
continue;
}
if (*s1 != ch)
return (*s1 < ch ? LESS : GREATER);
}
return (*s1 ? GREATER : EQUAL);
}
static void
usage(void)
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{
(void)fprintf(stderr, "usage: look [-df] [-t char] string [file ...]\n");
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exit(2);
}