1LSEARCH(3P) POSIX Programmer's Manual LSEARCH(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 lsearch, lfind — linear search and update
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15 #include <search.h>
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17 void *lsearch(const void *key, void *base, size_t *nelp, size_t width,
18 int (*compar)(const void *, const void *));
19 void *lfind(const void *key, const void *base, size_t *nelp,
20 size_t width, int (*compar)(const void *, const void *));
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23 The lsearch() function shall linearly search the table and return a
24 pointer into the table for the matching entry. If the entry does not
25 occur, it shall be added at the end of the table. The key argument
26 points to the entry to be sought in the table. The base argument points
27 to the first element in the table. The width argument is the size of an
28 element in bytes. The nelp argument points to an integer containing the
29 current number of elements in the table. The integer to which nelp
30 points shall be incremented if the entry is added to the table. The
31 compar argument points to a comparison function which the application
32 shall supply (for example, strcmp()). It is called with two arguments
33 that point to the elements being compared. The application shall ensure
34 that the function returns 0 if the elements are equal, and non-zero
35 otherwise.
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37 The lfind() function shall be equivalent to lsearch(), except that if
38 the entry is not found, it is not added to the table. Instead, a null
39 pointer is returned.
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42 If the searched for entry is found, both lsearch() and lfind() shall
43 return a pointer to it. Otherwise, lfind() shall return a null pointer
44 and lsearch() shall return a pointer to the newly added element.
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46 Both functions shall return a null pointer in case of error.
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49 No errors are defined.
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51 The following sections are informative.
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54 Storing Strings in a Table
55 This fragment reads in less than or equal to TABSIZE strings of length
56 less than or equal to ELSIZE and stores them in a table, eliminating
57 duplicates.
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60 #include <stdio.h>
61 #include <string.h>
62 #include <search.h>
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64 #define TABSIZE 50
65 #define ELSIZE 120
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67 ...
68 char line[ELSIZE], tab[TABSIZE][ELSIZE];
69 size_t nel = 0;
70 ...
71 while (fgets(line, ELSIZE, stdin) != NULL && nel < TABSIZE)
72 (void) lsearch(line, tab, &nel,
73 ELSIZE, (int (*)(const void *, const void *)) strcmp);
74 ...
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76 Finding a Matching Entry
77 The following example finds any line that reads "Thisisatest.".
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80 #include <search.h>
81 #include <string.h>
82 ...
83 char line[ELSIZE], tab[TABSIZE][ELSIZE];
84 size_t nel = 0;
85 char *findline;
86 void *entry;
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88 findline = "This is a test.\n";
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90 entry = lfind(findline, tab, &nel, ELSIZE, (
91 int (*)(const void *, const void *)) strcmp);
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94 The comparison function need not compare every byte, so arbitrary data
95 may be contained in the elements in addition to the values being com‐
96 pared.
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98 Undefined results can occur if there is not enough room in the table to
99 add a new item.
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102 None.
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105 None.
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108 hcreate(), tdelete()
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110 The Base Definitions volume of POSIX.1‐2017, <search.h>
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113 Portions of this text are reprinted and reproduced in electronic form
114 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
115 table Operating System Interface (POSIX), The Open Group Base Specifi‐
116 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
117 Electrical and Electronics Engineers, Inc and The Open Group. In the
118 event of any discrepancy between this version and the original IEEE and
119 The Open Group Standard, the original IEEE and The Open Group Standard
120 is the referee document. The original Standard can be obtained online
121 at http://www.opengroup.org/unix/online.html .
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123 Any typographical or formatting errors that appear in this page are
124 most likely to have been introduced during the conversion of the source
125 files to man page format. To report such errors, see https://www.ker‐
126 nel.org/doc/man-pages/reporting_bugs.html .
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130IEEE/The Open Group 2017 LSEARCH(3P)