Current File : //usr/share/doc/mawk/examples/qsort.awk
#!/usr/bin/mawk -f
# $MawkId: qsort.awk,v 1.4 2020/09/19 14:20:45 tom Exp $
# qsort text files
function middle(x,y,z) #return middle of 3
{
if ( x <= y )
{ if ( z >= y ) return y
if ( z < x ) return x
return z
}
if ( z >= x ) return x
if ( z < y ) return y
return z
}
function isort(A , n, i, j, hold)
{
# if needed a sentinel at A[0] will be created
for( i = 2 ; i <= n ; i++)
{
hold = A[ j = i ]
while ( A[j-1] > hold )
{ j-- ; A[j+1] = A[j] }
A[j] = hold
}
}
# recursive quicksort
function qsort(A, left, right ,i , j, pivot, hold)
{
pivot = middle(A[left], A[int((left+right)/2)], A[right])
i = left
j = right
while ( i <= j )
{
while ( A[i] < pivot ) i++
while ( A[j] > pivot ) j--
if ( i <= j )
{ hold = A[i]
A[i++] = A[j]
A[j--] = hold
}
}
if ( j - left > BLOCK ) qsort(A,left,j)
if ( right - i > BLOCK ) qsort(A,i,right)
}
BEGIN { BLOCK = 5 }
{ line[NR] = $0 "" # sort as string
}
END {
if ( NR > BLOCK ) qsort(line, 1, NR)
isort(line, NR)
for(ie = 1 ; ie <= NR ; ie++) print line[ie]
}
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