Useful Commands

Data rescue Have a dying disk? Better get the data off before it's too late! disk1 is the culprit in this example.

dd conv=noerror,sync if=/dev/disk1 of=/Volumes/whatever/backup.dmg

Encrypted and growable (sparse) disk image (-size specifies max growth)

hdiutil create dmg_name -size 1g -encryption -type SPARSE -fs HFS+ -volname Vault

Global find / replace

perl -pi -e 's/mandir=\'\${prefix}\/man\'/mandir=\'\${prefix}\/share\/man\'/g' configure

Disk Stats (zsh, all one line)

x=0 ; df -t hfs,afpfs | grep "/" | awk '{print $2}' | sed 's/G//g' | while read line ;\
do x=($line + $x); done ; echo "($x) / 1024 / 1024 / 2" | bc

Get console idle time

echo $((`ioreg -c IOHIDSystem | sed -e '/HIDIdleTime/ !{ d' -e 't' -e '}' -e 's/.* = //g' -e 'q'` / 1000000000))

Basic shell scripting idioms

simple for loop:

for file in `ls` 
do
mv $file $file.copy 
done

basic if statement:

if [ 1 = 1 ] ; then echo "yes" ; else echo "no" ; fi

tests (for cli args):

if ( ! [ $1 ] || [ ! $2 ] ) ; then echo "yup" ; else echo "nope" ; fi