qsort(3)                            CLIX                            qsort(3)



  NAME

    qsort - Provides a quick sort facility

  LIBRARY

    Standard C Library (libc.a)

  SYNOPSIS

    void qsort(
      char *base ,
      unsigned count ,
      int sizeof ,
      int *compar() );

  PARAMETERS

    base     This first element of the array of elements to be sorted

    count    The number of elements to be sorted

    sizeof   The size in characters of each element

    compar   A comparison function

  DESCRIPTION

    The qsort() function is an implementation of the quicker-sort algorithm.
    It sorts a table of data in place.

    The base parameter points to the element at the base of the table.  The
    count parameter specifies the number of elements in the table.  The
    comparison function, compar(), is called with two arguments that point to
    the elements being compared.  As the function must return an integer less
    than, equal to, or greater than zero, so must the first argument to be
    considered be less than, equal to, or greater than the second.

  EXAMPLES

    To sort a randomly generated set of numbers:

    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>

    #define SIZE 100

    /* Here is the comparison function! */
    int compare_ints(a, b)
    int *a, *b;



  2/94 - Intergraph Corporation                                              1

  qsort(3)                            CLIX                            qsort(3)



    {
         return((*a == *b) ? 0 : (*a < *b) ? -1 : 1);
    }

    main()
    {
         int i;
         int array[SIZE];

         for(i = 0; i < SIZE; ++i)
              array[i] = rand();
         qsort(array, SIZE, sizeof(int), (int (*)(const void *, const void *))
              compare_ints);
         for(i = 0; i < SIZE; ++i)
              printf("%i\n", array[i]);
    }


  NOTES

    The pointer to the base of the table should be of type pointer-to-element,
    and cast to type pointer-to-character.

    The comparison function need not compare every byte, so arbitrary data may
    be contained in the elements in addition to the values being compared.

    The order in the output of two items which compare as equal is
    unpredictable.

  RELATED INFORMATION

    Functions:  bsearch(3), lsearch(3), string(3)

    Commands:  sort(1)




















  2                                              Intergraph Corporation - 2/94