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Re: #!/usr/bin/env tclsh
- From: Bart Veer <bartv at ecoscentric dot com>
- To: Gary Thomas <gary at mlbassoc dot com>
- Cc: john at dallaway dot org dot uk, ecos-maintainers at ecos dot sourceware dot org
- Date: Fri, 06 Feb 2009 12:53:29 +0000
- Subject: Re: #!/usr/bin/env tclsh
- References: <496635B7.8060808@dallaway.org.uk> <pn4oz7g3d6.fsf@delenn.bartv.net> <498C2F1E.20609@mlbassoc.com>
>>>>> "Gary" == Gary Thomas <gary@mlbassoc.com> writes:
Gary> Bart Veer wrote:
>>>>>>> "John" == John Dallaway <john@dallaway.org.uk> writes:
>>
John> This patch simplifies the #! magic used to invoke Tcl
John> scripts by using "/usr/bin/env tclsh" to find the tclsh
John> executable. Very old Cygwin installations providing only
John> tclsh83.exe or cygtclsh80.exe are no-longer supported.
John> Checked-in.
>>
>> Actually, this patch has broken things in various ways. Consider e.g.
>> file2c.tcl in the romfs package. The CDL invokes this using e.g.:
>>
>> sh file2c.tcl testromfs_le.bin testromfs_le.h
>>
>> With the old magic this still worked fine because sh would ignore the
>> #! at the start completely and move on to the 'exec sh -c' on line 3.
>> With the new '#!/usr/bin/env tclsh' the sh invocation ignores the
>> #! comment on line 1 so ends up trying to run the whole Tcl script as
>> a shell script. Needless to say this is not very successful.
>>
>> io/framebuf is similarly affected. services/memalloc/common is not. I
>> have not yet checked all the other packages that use Tcl scripts.
>>
>> Possible solutions are:
>>
>> 1) revert the change
>> 2) remove the 'sh' bits from the relevant CDL scripts, treating the
>> Tcl script as plain executables.
>> 3) make the CDL invoke /usr/bin/env tclsh directly, treating the
>> Tcl scripts as Tcl scripts.
>>
>> (1) would be a bad move. I think I would prefer (3) to (2).
Gary> Why isn't this working? According to 'man sh' on my Linux
Gary> system:
Gary> If the program is a file beginning with #!, the
Gary> remainder of the first line specifies an interpreter
Gary> for the program. The shell executes the specified
Gary> interpreter on operating systems that do not han- dle
Gary> this executable format themselves. The arguments to
Gary> the interpreter consist of a single optional argument
Gary> following the interpreter name on the first line of
Gary> the program, followed by the name of the program,
Gary> followed by the command arguments, if any.
Gary> It would seem that since Linux *does* handle this directly, 'sh'
Gary> chooses to ignore it :-(
If you run 'sh xx' instead of just 'xx', is 'xx' still a "program" by
the above definition is or is it just data for sh? I don't know the
official answer, but it appears that Linux sh treats it as just data.
Gary> In any case, I vote for (2), otherwise you may end up with
Gary> the same problem all of this was trying to fix in the first
Gary> place, namely not knowing where/how to find 'tclsh'
Hence the "/usr/bin/env tclsh" in the CDL script as opposed to just
"tclsh". Although come to think of it, I am not sure that gains
anything. Either make (or the shell invoked by make) or the env
utility will end up searching PATH for tclsh.
Bart
--
Bart Veer eCos Configuration Architect
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