1LSEARCH(3P)                POSIX Programmer's Manual               LSEARCH(3P)
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PROLOG

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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11

NAME

13       lsearch, lfind — linear search and update
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SYNOPSIS

16       #include <search.h>
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18       void *lsearch(const void *key, void *base, size_t *nelp, size_t width,
19           int (*compar)(const void *, const void *));
20       void *lfind(const void *key, const void *base, size_t *nelp,
21           size_t width, int (*compar)(const void *, const void *));
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DESCRIPTION

24       The lsearch() function shall linearly search the  table  and  return  a
25       pointer  into  the  table for the matching entry. If the entry does not
26       occur, it shall be added at the end of  the  table.  The  key  argument
27       points to the entry to be sought in the table. The base argument points
28       to the first element in the table. The width argument is the size of an
29       element in bytes. The nelp argument points to an integer containing the
30       current number of elements in the table.  The  integer  to  which  nelp
31       points  shall  be  incremented  if the entry is added to the table. The
32       compar argument points to a comparison function which  the  application
33       shall  supply (for example, strcmp()).  It is called with two arguments
34       that point to the elements being compared. The application shall ensure
35       that  the  function  returns  0 if the elements are equal, and non-zero
36       otherwise.
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38       The lfind() function shall be equivalent to lsearch(), except  that  if
39       the  entry is not found, it is not added to the table.  Instead, a null
40       pointer is returned.
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RETURN VALUE

43       If the searched for entry is found, both lsearch()  and  lfind()  shall
44       return  a pointer to it. Otherwise, lfind() shall return a null pointer
45       and lsearch() shall return a pointer to the newly added element.
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47       Both functions shall return a null pointer in case of error.
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ERRORS

50       No errors are defined.
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52       The following sections are informative.
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EXAMPLES

55   Storing Strings in a Table
56       This fragment reads in less than or equal to TABSIZE strings of  length
57       less  than  or  equal to ELSIZE and stores them in a table, eliminating
58       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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79           #include <search.h>
80           #include <string.h>
81           ...
82           char line[ELSIZE], tab[TABSIZE][ELSIZE];
83           size_t nel = 0;
84           char *findline;
85           void *entry;
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87           findline = "This is a test.\n";
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89           entry = lfind(findline, tab, &nel, ELSIZE, (
90               int (*)(const void *, const void *)) strcmp);
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APPLICATION USAGE

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.
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97       Undefined results can occur if there is not enough room in the table to
98       add a new item.
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RATIONALE

101       None.
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FUTURE DIRECTIONS

104       None.
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SEE ALSO

107       hcreate(), tdelete()
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109       The Base Definitions volume of POSIX.1‐2008, <search.h>
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112       Portions  of  this text are reprinted and reproduced in electronic form
113       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
114       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
115       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
116       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
117       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/online.html .
122
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                  2013                          LSEARCH(3P)
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