What is the purpose of using #!/usr/bin/env <sh|bash|python> shebang compared to #!/bin/bash, #!/bin/sh or #!/usr/bin/python?
Some people might use a different python (perl, etc.) than the system one. /usr/bin/env python would run the version configured as the current one, possibly making the script more portable.
On the other hand, reportedly, some systems do not have /usr/bin/env. Also, you cannot use #!/usr/bin/env foo x as a replacement for #!foo x, because foo x will be interpreted as a single argument. So the value of the approach is debatable.
