ref: c05dd199c1e5250f443d44a41144b79d8a98994c
dir: /sys/src/cmd/upas/binscripts/tfmt.rc/
#!/bin/rc
# anti-topposting defense
# sed '/^[ ]*>[ ]*>[ ]*>/q'
awk '
{
if(l[i] ~ /^[ ]*>[ ]*>[ ]*>/)
q = 1
if(q == 0)
l[i = NR] = $0;
}
END{
for(; i > 1; i--)
if(l[i] !~ /^([ ]*>)*[ ]*$/)
break;
for(; i > 1; i--)
if(l[i] !~ /^[ ]*>[ ]*>/)
break;
for(; i > 1; i--)
if(l[i] !~ /^([ ]*>)*[ ]*$/)
break;
for(j = 1; j <= i; j++)
print l[j]
}' |dd -conv block >[2=]