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lsearch(3p) — Linux manual page

LSEARCH(3P)             POSIX Programmer's ManualLSEARCH(3P)

PROLOG        top

       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        top

       lsearch, lfind — linear search and update

SYNOPSIS        top

       #include <search.h>       void *lsearch(const void *key, void *base, size_t *nelp, size_twidth,           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        top

       Thelsearch() 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. Thekey       argument points to the entry to be sought in the table. Thebase       argument points to the first element in the table. Thewidth       argument is the size of an element in bytes. Thenelp argument       points to an integer containing the current number of elements in       the table. The integer to whichnelp points shall be incremented       if the entry is added to the table. Thecompar 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.       Thelfind() function shall be equivalent tolsearch(), except that       if the entry is not found, it is not added to the table.  Instead,       a null pointer is returned.

RETURN VALUE        top

       If the searched for entry is found, bothlsearch() andlfind()       shall return a pointer to it. Otherwise,lfind() shall return a       null pointer andlsearch() shall return a pointer to the newly       added element.       Both functions shall return a null pointer in case of error.

ERRORS        top

       No errors are defined.The following sections are informative.

EXAMPLES        top

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        top

       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        top

       None.

FUTURE DIRECTIONS        top

       None.

SEE ALSO        top

hcreate(3p),tdelete(3p)       The Base Definitions volume of POSIX.1‐2017,search.h(0p)

COPYRIGHT        top

       Portions of this text are reprinted and reproduced in electronic       form from IEEE Std 1003.1-2017, Standard for Information       Technology -- Portable Operating System Interface (POSIX), The       Open Group Base Specifications Issue 7, 2018 Edition, Copyright       (C) 2018 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 Standard,       the original IEEE and The Open Group Standard is the referee       document. The original Standard can be obtained online athttp://www.opengroup.org/unix/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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017LSEARCH(3P)

Pages that refer to this page:search.h(0p), bsearch(3p), hcreate(3p), lfind(3p), tdelete(3p)

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