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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 dif-
       fer (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 ta-
       ble. The compar argument points to a comparison function which the application shall supply (for example,  str-
       cmp()).   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 "This is a test."  .


              #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 compared.

       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(), tsearch(), the Base Definitions volume of IEEE Std 1003.1-2001, <search.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,  Inc  and  The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                          LSEARCH(3P)