QSORT(3) C LIBRARY FUNCTIONS QSORT(3)
NAME
qsort - quicker sort
SYNOPSIS
qsort(base, nel, width, compar)
char *base;
int (*compar)();
DESCRIPTION
qsort() is an implementation of the quicker-sort algorithm.
It sorts a table of data in place.
base points to the element at the base of the table. nel is
the number of elements in the table. width is the size, in
bytes, of each element in the table. compar is the name of
the comparison function, which 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.
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.
SEE ALSO
sort(1V), bsearch(3), lsearch(3), string(3)
EXAMPLE
The following program sorts a simple array:
static int intcompare(i,j)
int *i, *j;
{
return(*i - *j);
}
main()
{
int a[10];
int i;
a[0] = 9;
a[1] = 8;
a[2] = 7;
a[3] = 6;
a[4] = 5;
a[5] = 4;
a[6] = 3;
a[7] = 2;
a[8] = 1;
a[9] = 0;
qsort(a,10,sizeof(int),intcompare)
for (i=0; i<10; i++) printf(" %d",a[i]);
printf("\n");
}
Sun Release 4.1 Last change: 16 February 1988
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