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LSEARCH(3P)                POSIX Programmer's Manual               LSEARCH(3P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       lsearch, lfind -- linear search and update
SYNOPSIS
       #include <search.h>
       void *lsearch(const void *key, void *base, size_t *nelp, size_t width,
           int (*compar)(const void *, const void *));
       void *lfind(const void *key, const void *base, size_t *nelp,
           size_t width, int (*compar)(const void *, const void *));
DESCRIPTION
       The lsearch() function shall linearly search the  table  and  return  a
       pointer  into  the  table for the matching entry. If the entry does not
       occur, it shall be added at the end of  the  table.  The  key  argument
       points to the entry to be sought in the table. The base argument points
       to the first element in the table. The width argument is the size of an
       element in bytes. The nelp argument points to an integer containing the
       current number of elements in the table.  The  integer  to  which  nelp
       points  shall  be  incremented  if the entry is added to the table. The
       compar argument points to a comparison function which  the  application
       shall  supply (for example, strcmp()).  It is called with two arguments
       that point to the elements being compared. The application shall ensure
       that  the  function  returns  0 if the elements are equal, and non-zero
       otherwise.
       The lfind() function shall be equivalent to lsearch(), except  that  if
       the  entry is not found, it is not added to the table.  Instead, a null
       pointer is returned.
RETURN VALUE
       If the searched for entry is found, both lsearch()  and  lfind()  shall
       return  a pointer to it. Otherwise, lfind() shall return a null pointer
       and lsearch() shall return a pointer to the newly added element.
       Both functions shall return a null pointer in case of error.
ERRORS
       No errors are defined.
       The following sections are informative.
EXAMPLES
   Storing Strings in a Table
       This fragment reads in less than or equal to TABSIZE strings of  length
       less  than  or  equal to ELSIZE and stores them in a table, eliminating
       duplicates.
           #include <stdio.h>
           #include <string.h>
           #include <search.h>
           #define TABSIZE 50
           #define ELSIZE 120
           ...
               char line[ELSIZE], tab[TABSIZE][ELSIZE];
               size_t nel = 0;
               ...
               while (fgets(line, ELSIZE, stdin) != NULL && nel < TABSIZE)
                   (void) lsearch(line, tab, &nel,
                       ELSIZE, (int (*)(const void *, const void *)) strcmp);
               ...
   Finding a Matching Entry
       The following example finds any line that reads "Thisisatest.".
           #include <search.h>
           #include <string.h>
           ...
           char line[ELSIZE], tab[TABSIZE][ELSIZE];
           size_t nel = 0;
           char *findline;
           void *entry;
           findline = "This is a test.\n";
           entry = lfind(findline, tab, &nel, ELSIZE, (
               int (*)(const void *, const void *)) strcmp);
APPLICATION USAGE
       The comparison function need not compare every byte, so arbitrary  data
       may  be  contained in the elements in addition to the values being com-
       pared.
       Undefined results can occur if there is not enough room in the table to
       add a new item.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       hcreate(), tdelete()
       The Base Definitions volume of POSIX.1-2008, <search.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                          LSEARCH(3P)