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Re: Colon on first line ignored

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February 2, 2016 01:15
Re: Colon on first line ignored
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Eric Brine wrote:
>Can anyone explain why a colon on the first line is ignored?

That'll be due to the old convention, predating shebang, for
distinguishing script interpreters.  The arrangement is that a script
starting with a line containing only colon is taken to be a sh script,
and a script starting with a hash is taken to be a csh script.  In sh,
colon is a no-op command; it predates the availability of hash-introduced
comments in Bourne shells.  On a system using this convention, you can
make a Perl script work by starting it with a colon line followed by one
of the well-known duoglot formulations to make sh feed the script to Perl.
For this to work requires that Perl skip the initial colon line.


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