Gordon Messmer gordon.messmer@gmail.com wrote:
I'm reasonably certain that a script with no shebang will run with /bin/sh. I interpret your statement to mean that if a user is using ksh and enters the path to such a script, it would also run in ksh. That would only be true if you "sourced" the script from your shell.
The historical way is: there is only one shell and all scripts are Bourne Shell scripts.
Then csh came out and some people really thought is was a good idea to write csh scripts. So someone decided to mark csh scripts with an initial "#". Note that at that time, the Bourne Shell did not support "#" as a comment sign and thus scripts with an inital "#" have been illegal Bourne Shell scripts.
Later BSD came out with #!name and all but AT&T adopted to this.
In the mid 1980s, AT&T introduced an initial ":" to mark Bourne Shell scripts.
In 1989, with the beginning of SVr4, even AT&T introduced #!name, but the AT&T variant of the OS did not correct their scripts, so if you are on a UnixWare installation, you will have fun.
Unfortunately, POSIX cannot standardize #!name. This is because POSIX does not standardize PATHs and because the scripts marked that way would need to be scripts that call the POSIX shell. The official method to get a POSIX shell is to call this:
sh # to make sure you have a Bourne Shell alike PATH=`getconf PATH` # to get a POSIX compliant PATH sh # to get a POSIX shell, that muust be the first # 'sh' in the POSIX PATH
/bin/sh definitely does not start a POSIX shell.....
Jörg