Question

Is it possible to specify a shebang line without knowing the path of the program you want to do the executing?

maybe don’t specify the path

#!node

or specify several options

#!/usr/local/bin/node
#!/usr/bin/node

Extra points for cross platform solution (various flavors of linux, BSD, OSX etc…)

Answer 1

/usr/bin/env is specifically thought of for cross-platform solutions.

env executes utility after modifying the environment as specified on
the command line.  The option name=value specifies an environmental
variable, name, with a value of value.  The option `-i' causes env
to completely ignore the environment it inherits.

If no utility is specified, env prints out the names and values of
the variables in the environment, with one name=value pair per line.

so something in lines of:

#!/usr/bin/env node

Will be cross-platform and “the right way to go”.