|There's more than one way to do things|
Re^2: open and read text fileby afoken (Chancellor)
|on Jul 25, 2017 at 06:21 UTC||Need Help??|
I think the Shebang thing, although valid, is a red herring.
Other things may happen:
Bad interpreter, i.e. the program after #! could not be found. The Mac error message is at least similar.
Interpreter not executable:
Shebang not identified as such:
This also happens when there is an (invisible) Byte Order Mark (BOM) at the start of the file. What happens here?
The shell attempts to start ./shebang.pl via fork() and exec(), as usual. This will fail, because the kernel can't identify the file as binary executable or script with some interpreter (first two bytes aren't #!). At this point, a legacy mechanism in the shell kicks in. In the very early days of Unix, shell scripts did not have to have the shebang. If you chmod +x any text file and try to run it, but exec() fails, the shell will attempt to read it as a shell script. A little experiment shows this:
A little trick to ensure you don't run into the BOM trap:
This test must return 35 or the script does not start with the shebang. 10 is a LF, the end of the first line. 13 is CR, the end of the first line with MS-DOS or classic Mac line-endings, 32 is a space, 9 is a tab. Byte Order Marks may show up as 239 (UTF-8), 254 (UTF-16 BE), 255 (UTF-16 LE or UTF-32 LE), 0 (UTF-32 BE), 43 (UTF-7), 247 (UTF-1).
See also Re^2: Shebang behavior with perl
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)