1LSEARCH(P) POSIX Programmer's Manual LSEARCH(P)
2
6 lsearch, lfind - linear search and update
7
9 #include <search.h>
10 void *lsearch(const void *key, void *base, size_t *nelp, size_t width,
12 int (*compar)(const void *, const void *));
13 void *lfind(const void *key, const void *base, size_t *nelp,
14 size_t width, int (*compar)(const void *, const void *));
15
18 The lsearch() function shall linearly search the table and return a
19 pointer into the table for the matching entry. If the entry does not
20 occur, it shall be added at the end of the table. The key argument
21 points to the entry to be sought in the table. The base argument points
22 to the first element in the table. The width argument is the size of an
23 element in bytes. The nelp argument points to an integer containing the
24 current number of elements in the table. The integer to which nelp
25 points shall be incremented if the entry is added to the table. The
26 compar argument points to a comparison function which the application
27 shall supply (for example, strcmp()). It is called with two arguments
28 that point to the elements being compared. The application shall ensure
29 that the function returns 0 if the elements are equal, and non-zero
30 otherwise.
31 The lfind() function shall be equivalent to lsearch(), except that if
33 the entry is not found, it is not added to the table. Instead, a null
34 pointer is returned.
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37 If the searched for entry is found, both lsearch() and lfind() shall
38 return a pointer to it. Otherwise, lfind() shall return a null pointer
39 and lsearch() shall return a pointer to the newly added element.
40 Both functions shall return a null pointer in case of error.
42
44 No errors are defined.
45 The following sections are informative.
47
49 Storing Strings in a Table
50 This fragment reads in less than or equal to TABSIZE strings of length
51 less than or equal to ELSIZE and stores them in a table, eliminating
52 duplicates.
53 #include <stdio.h>
56 #include <string.h>
57 #include <search.h>
58 #define TABSIZE 50
61 #define ELSIZE 120
62 ...
65 char line[ELSIZE], tab[TABSIZE][ELSIZE];
66 size_t nel = 0;
67 ...
68 while (fgets(line, ELSIZE, stdin) != NULL && nel < TABSIZE)
69 (void) lsearch(line, tab, &nel,
70 ELSIZE, (int (*)(const void *, const void *)) strcmp);
71 ...
72 Finding a Matching Entry
74 The following example finds any line that reads "This is a test." .
75 #include <search.h>
78 #include <string.h>
79 ...
80 char line[ELSIZE], tab[TABSIZE][ELSIZE];
81 size_t nel = 0;
82 char *findline;
83 void *entry;
84 findline = "This is a test.\n";
87 entry = lfind(findline, tab, &nel, ELSIZE, (
90 int (*)(const void *, const void *)) strcmp);
91
93 The comparison function need not compare every byte, so arbitrary data
94 may be contained in the elements in addition to the values being com‐
95 pared.
96 Undefined results can occur if there is not enough room in the table to
98 add a new item.
99
101 None.
102
104 None.
105
107 hcreate() , tsearch() , the Base Definitions volume of
108 IEEE Std 1003.1-2001, <search.h>
109
111 Portions of this text are reprinted and reproduced in electronic form
112 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
113 -- Portable Operating System Interface (POSIX), The Open Group Base
114 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
115 Electrical and Electronics Engineers, Inc and The Open Group. In the
116 event of any discrepancy between this version and the original IEEE and
117 The Open Group Standard, the original IEEE and The Open Group Standard
118 is the referee document. The original Standard can be obtained online
119 at http://www.opengroup.org/unix/online.html .
120IEEE/The Open Group 2003 LSEARCH(P)