Split access.log to days

awk '
BEGIN {
m2n["Jan"] = 1; m2n["Feb"] = 2; m2n["Mar"] = 3; m2n["Apr"] = 4;
m2n["May"] = 5; m2n["Jun"] = 6; m2n["Jul"] = 7; m2n["Aug"] = 8;
m2n["Sep"] = 9; m2n["Oct"] = 10; m2n["Nov"] = 11; m2n["Dec"] = 12;
}
{
split($4, a, "[]/:[]")
if(a[4] != pyear || a[3] != pmonth || a[2] != pday) {
pyear = a[4]
pmonth = a[3]
pday = a[2]

if(fname != "")
close(fname)

fname = sprintf("access_%04d-%02d-%02d.log", a[4], m2n[a[3]], a[2])
}
print >> fname
}'

By jwadsack.