Riddle me this Batman! POSIXLY_CORRECT effect on wc

[Bob Bell]

On Wed, Nov 20, 2002 at 09:48:18AM -0500, Steven W. Orr <steveo at syslang.net> wrote:
> I'm trying to get control of some formating that's supposed to be under 
> the control of the environment variable POSIXLY_CORRECT. (I can work 
> around it but I want to understand this too.)
> 
> 663 > wc -l < ~/.bashrc
>     195
> 664 > POSIXLY_CORRECT=1 wc -l < ~/.bashrc
> 195
> 
> So far so good. POSIXLY_CORRECT is needed to eliminate the leading spaces.
> 
> 665 > foo=$(wc -l < ~/.bashrc)
> 666 > echo $foo
> 195
> 
> Huh? How does this happen. I expected four leading spaces!

That's because of how the shell is interpretting what you say on the
command line.

$ foo=$(wc -l < ~/.bashrc)
$ echo $foo            #<-- Evaluated as: echo     157
157
$ echo "$foo"          #<-- Evaluated as: echo "    157"
    157
$ 

In the first, the first argument is "157", because of the way the shell
parses the command line.  In the second, the first argument is
"    157", which is what you expected.

> 671 > cat ~/xxx.sh 
> #! /bin/bash
> 
> foo=$(wc -l < ~/.bashrc)
> echo "There are $foo lines in bashrc"
> POSIXLY_CORRECT=1 foo=$(wc -l < ~/.bashrc)
> echo "There are $foo lines in bashrc"
> 
> 672 > ~/xxx.sh
> There are     195 lines in bashrc
> There are     195 lines in bashrc
> 673 > POSIXLY_CORRECT=1 ~/xxx.sh
> There are 195 lines in bldmaster
> There are 195 lines in bldmaster
> 674 > 
> 
> I'm totally mystified. Can someone *please* explain this one to me? :-(

Line 5 in xxx.sh is not passing POSIXLY_CORRECT=1 to the sub-shell that
executes the $() contents.  Try replacing it with:

foo=$(POSIXLY_CORRECT=1 wc -l < ~/.bashrc)

to get the behavior you expect.  Or another way:

export POSIXLY_CORRECT=1
foo=$(wc -l < ~/.bashrc)


-- 
Bob Bell <bobbell at zk3.dec.com>
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