Re: [Boost-build] SHELL and trailing newlines

From: Rene Rivera (grafikrobot_at_[hidden])
Date: 2006-10-04 15:08:56

Vladimir Prus wrote:
> Hi,
> at the moment it's not easy to use SHELL with pkg-config, like this:
> 
>    LIBXML_INCLUDES = [ SHELL "pkg-config --cflags libxml-2.0" ] ;
> 
> because pkg-config outputs a trailing newline, and then
>   
>     <cflags>$(LIBXML_INCLUDES)
> 
> apparently does not work. Unix shell, when it process command substitution, 
> e.g.
> 
>        `pkg-config --cflags libxml-2.0`
> 
> removes trailing newline. I wonder if we should do the same in SHELL?

Actually it doesn't have to do with specifically with the trailing 
newline. In Unix shells, bash, sh, ksh, etc. it will filter the output 
of command output as arguments (``) such that it replaces all new-lines 
with a space. For example try doing "echo `ls -1`". Since we have to 
handle the case where want to see the new-lines, i.e. the complete raw 
output I'd suggest adding another output processing option to 
SHELL/COMMAND to act as the CLI shell do. Perhaps an "eol-delimited-output":

   LIBXML_INCLUDES = [ SHELL "pkg-config --cflags libxml-2.0" : 
eol-delimited-output ] ;

One might want to implement a 'ws-delimited-output' at the same time :-)

-- 
-- Grafik - Don't Assume Anything
-- Redshift Software, Inc. - http://redshift-software.com
-- rrivera/acm.org - grafik/redshift-software.com
-- 102708583/icq - grafikrobot/aim - grafikrobot/yahoo