I wish to replace my failing memory with a very small shell script.

#!/bin/sh

if ! [ –a $1.sav ]; then

    mv $1 $1.sav

    cp $1.sav $1

fi

nano $1 

is intended to save the original version of a script. If the original has been preserved before, it skips the move-and-copy-back (and I use move-and-copy-back to preserve the original timestamp).

This works as intended if, after I make it executable with chmod I launch it from within the directory where I am editing, e.g. with

./safe.sh filename

However, when I move it into /usr/bin (so it is in the path as verified with echo $PATH) and then I try to run it in a different directory (without the leading ./ ) it fails with

-bash: /usr/bin/safe.sh: /bin/sh: bad interpreter: Text file busy

D'oh? Inquiring minds want to know how to make this work.