*nix script snippets that are useful/clever

#Backup & clear history
DATE=`date +%Y%m%d-%H%M`
mv ~/.zsh_history{,.$DATE}
cat /dev/null > ~/.zsh_history

#HDD space (without clutter)
df -h | grep -v "tmp\|udev"

#send contents into a file (you need to \escape any \$variables within the CONTENTS+COMMANDS)
cat <<EOF > /path/to/file/to/create
CONTENTS+COMMANDS
EOF

#inline string replacement in config file
sed -i "s/SELINUX=enforcing/SELINUX=disabled/g" /etc/selinux/config;
#OR (IF you have perl installed)
perl -pi -e 's|SELINUX=enforcing|SELINUX=disabled|'  /etc/selinux/config;

#To list TCP listening ports, with name of each listener’s daemon and its PID
sudo netstat -plnt | grep -i listen