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 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*

My question is, when I move this script into the path (verified by echo $PATH) why does it then fail?

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