Post History

Replacing the shebang in a script

In a Bash script and/or at the command line, given that `$file` is the path to an executable text file with a shebang, and `$env` is a valid shebang, I want to replace the existing shebang in the file with the new one. Is there a standard or well-known way?

I thought of `echo`ing the new shebang and then `tail`ing the rest of the file, but this requires explicitly making a temporary file and replacing the original with it (and possibly fixing mode/owner).

I also thought of using `sed`, but I can't quite figure it out given that shebangs generally contain multiple forward slashes which interfere with the regex syntax. It also seems like overkill since only the first line needs to be considered for replacement.