\input introduces space

\input introduces space

[Peter Münster]

Hello,
\input seems to introduce a space. Example:

\starttext
\immediate\write18{echo -n X >bla.tex}
X\input bla\relax X
\stoptext

How could I get rid of this space?

Cheers, Peter

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http://pmrb.free.fr/contact/

Re: \input introduces space

[Taco Hoekwater]

Hi Peter,

Not the \input command, but the end-of-line in the inputted file
is creating the space, indirectly. TeX normally appends a character
with the current value of \endlinechar to each line of an input-ed
file, and that character is later converted to a space.

Setting \endlinechar to -1 temporarily is a possibility, another
is writing a percent sign to the end of the line, yet another is
ending the written line with \relax (or a similar space-gobbling
command), and finally changing the catcode of the current
\endlinechar to 9 (ignored) also works.

Cheers, Taco

Peter Münster wrote:
> Hello,
> \input seems to introduce a space. Example:
> 
> \starttext
> \immediate\write18{echo -n X >bla.tex}
> X\input bla\relax X
> \stoptext
> 
> How could I get rid of this space?
> 
> Cheers, Peter
> 

Re: \input introduces space

[Taco Hoekwater]

Taco Hoekwater wrote:
> Setting \endlinechar to -1 temporarily is a possibility, another
> is writing a percent sign to the end of the line, yet another is
> ending the written line with \relax (or a similar space-gobbling
> command), and finally changing the catcode of the current
> \endlinechar to 9 (ignored) also works.

Here is a file demonstrating all four:


\starttext

% 1
\immediate\write18{echo -n X >bla1.tex}
X{\endlinechar=-1 \input bla1 }X

% 2
\immediate\write18{echo -n X\letterpercent >bla2.tex}
X\input bla2 X

% 3
\immediate
   \write18
     {echo -n X\letterbackslash\letterbackslash relax >bla3.tex}
X\input bla3 X

% 4
\immediate\write18{echo -n X >bla4.tex}
X{\catcode`\^^M=9 \input bla4 }X

\stoptext

Re: \input introduces space

[Peter Münster]

On Tue, 28 Feb 2006, Taco Hoekwater wrote:

> Taco Hoekwater wrote:
> > Setting \endlinechar to -1 temporarily is a possibility, another
> > is writing a percent sign to the end of the line, yet another is
> > ending the written line with \relax (or a similar space-gobbling
> > command), and finally changing the catcode of the current
> > \endlinechar to 9 (ignored) also works.
> 
> Here is a file demonstrating all four:

Hello Taco,
thanks a lot for your solutions, one can even omit the "-n" now!
Cheers, Peter

-- 
http://pmrb.free.fr/contact/

Re: \input introduces space

[Hans Hagen]

Taco Hoekwater wrote:
> Hi Peter,
>
> Not the \input command, but the end-of-line in the inputted file
> is creating the space, indirectly. TeX normally appends a character
> with the current value of \endlinechar to each line of an input-ed
> file, and that character is later converted to a space.
>
> Setting \endlinechar to -1 temporarily is a possibility, another
> is writing a percent sign to the end of the line, yet another is
> ending the written line with \relax (or a similar space-gobbling
> command), and finally changing the catcode of the current
> \endlinechar to 9 (ignored) also works.
>
> Cheers, Taco
>
> Peter M�nster wrote:
>   
>> Hello,
>> \input seems to introduce a space. Example:
>>
>> \starttext
>> \immediate\write18{echo -n X >bla.tex}
>> X\input bla\relax X
>> \stoptext
>>
>> How could I get rid of this space?
>>
>> Cheers, Peter
>>
>>     
in addition to taco's answers: 

X\ignorespaces \input bla\relax \removeunwantedspaces X

can help you out; 

btw, can you wikify taco's response? somewhere under 'how tex reads input'; in due time we can then add some additional info about how scantokens etc behave (everyeof stuff and such) 

Hans 

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Re: \input introduces space

[Peter Münster]

On Tue, 28 Feb 2006, Hans Hagen wrote:

> btw, can you wikify taco's response? somewhere under 'how tex reads
> input'; in due time we can then add some additional info about how
> scantokens etc behave (everyeof stuff and such)

Of course, but it won't be possible the next 10 days, so be patient.
Cheers, Peter

-- 
http://pmrb.free.fr/contact/