ICMP echo request alias ping:
perl -MNet::Ping -lne 'print "$_: ", scalar Net::Ping->new( "icmp" )->ping( $_ )' hosts.txt
TCP based ping using port 80:
perl -MNet::Ping -lne '$p = Net::Ping->new; $p->port_number( 80 );
                       print "$_: ", scalar $p->ping( $_ )' hosts.txt

Blocking Traffic Using Null Route

Blocking network traffic for a specific host without using iptables:
ip route add blackhole
To remove the rule:
ip route del blackhole
Compared to iptables a null route has no effect on loopback addresses (

Erase Old Files

Erase files older than 7 days:
find -mtime +7 -exec rm -rf {} \;

Git Tagging

Add an annotated tag:
git tag -a v1.0.0 -m 'release 1.0.0'
Push tag changes to remote repositories:
git push --tags
Remove a tag:
git tag -d v1.0.0
Remove a tag from remote repositories:
git tag -d v1.0.0
git push origin :refs/tags/v1.0.0