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Интерактивная система просмотра системных руководств (man-ов)

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lsearch (3)
  • lsearch (3) ( Solaris man: Библиотечные вызовы )
  • lsearch (3) ( FreeBSD man: Библиотечные вызовы )
  • lsearch (3) ( Русские man: Библиотечные вызовы )
  • lsearch (3) ( Linux man: Библиотечные вызовы )
  • >> lsearch (3) ( POSIX man: Библиотечные вызовы )
  •  

    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 "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, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications 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 Standard, 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 .


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUE
    ERRORS
    EXAMPLES
    Storing Strings in a Table
    Finding a Matching Entry
    APPLICATION USAGE
    RATIONALE
    FUTURE DIRECTIONS
    SEE ALSO
    COPYRIGHT


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