In article <[EMAIL PROTECTED]>, Adriano Ferreira <[EMAIL PROTECTED]> wrote:
> Hey, that's not fair. In your illustration above, does 'python' can be > found in the PATH? That is, > > $ python /tmp/hello.py > > works? If it does, probably > > #!/usr/bin/python > #!/usr/bin/env python > #!python > > would also work if > (1) 'python' is at '/usr/bin/python' (but that's inflexible) > (2) 'python' can be found in the environment variable path (if 'env' > is at '/usr/bin/env') > (3) 'python' can be found in the environment variable path (no need > for 'env' utility) Contrary to popular belief, #! is not intended for the shell, but rather for the execve(2) system call of the UNIX operating system. These two characters form the 16 bit "magic number" of interpreter files. Any executable file must start with a 16 bit field that identifies it so the operating system will know how to execute it. In the case of a #! interpreter file, the operating system expects the rest of that line to be the path to the file. PATH is not searched, and is irrelevant. The only way #!python can work, is if it's in the current working directory. Just to help make it confusing, when this mechanism fails and execve(2) returns an error, most shells will go on to try to execute the file themselves, regardless of whether there's a #! or not. csh (the shell language that doesn't look anything like C, Bill Joy's attempt at language design before he started over with Java) does that only if the first line is "#"; otherwise it invokes the Bourne shell. Donn Cave, [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
