Answer by Big Rich for sed in-place flag that works both on Mac (BSD) and Linux

Steve Powell's answer is quite correct, consulting the MAN page for sed on OSX and Linux (Ubuntu 12.04) highlights the in-compatibility within 'in-place' sed usage across the two operating systems.

JFYI, there should be no space between the -i and any quotes (which denote an empty file extension) using the Linux version of sed, thus

sed Linux Man Page

#Linuxsed -i""

and

sed OSX Man page

#OSX (notice the space after the '-i' argument)sed -i ""

I got round this in a script by using an alias'd command and the OS-name output of 'uname' within a bash 'if'. Trying to store OS-dependant command strings in variables was hit and miss when interpreting the quotes. The use of 'shopt -s expand_aliases' is necessary in order to expand/use the aliases defined within your script. shopt's usage is dealt with here.