stracing pwd

stracing pwd

[David Eduardo Gómez Noguera]

Hellow. This just striked me.
I wondered how pwd works, I entered a linked directory, and pwd gives me
the link.
when I tried pwd -h (wrong argument) I saw there are two possible
arguments
I have 
/usr/src/linux-2.6.7
/usr/src/linux -> /usr/src/linux-2.6.7

under /usr/src/linux, 
pwd prints /usr/src/linux
pwd -L too
pwd -P prints /usr/src/linux-2.6.7
but an strace always shows the same
write(1, "/usr/src/linux-2.6.7\n", 21/usr/src/linux-2.6.7
)  = 21
and it prints /usr/src/linux-2.6.7 to stdout no matter the parameter
given to pwd.

Anyone knows why that could happen? 
( I haven't seen to the pwd code yet though)

Re: stracing pwd

[Christoph Bussenius]

On Sat, Jun 19, 2004 at 10:29:40AM -0500, David Eduardo Gómez Noguera wrote:
> /usr/src/linux-2.6.7
> /usr/src/linux -> /usr/src/linux-2.6.7
> 
> under /usr/src/linux, 
> pwd prints /usr/src/linux
> pwd -L too
> pwd -P prints /usr/src/linux-2.6.7
> but an strace always shows the same
> write(1, "/usr/src/linux-2.6.7\n", 21/usr/src/linux-2.6.7
> )  = 21
> and it prints /usr/src/linux-2.6.7 to stdout no matter the parameter
> given to pwd.
> 
> Anyone knows why that could happen? 
> ( I haven't seen to the pwd code yet though)

The difference is that the first time you call pwd, you actually call
the shell builtin named pwd. The second time you call pwd, you call
/bin/pwd. The shell thinks you are where you have cd'd to, but in fact,
you are in /usr/src/linux-2.6.7. Just try typing /bin/pwd in the shell.

Cheers,
Christoph

-- 
``There's no dark side of the moon, really
Matter of fact, it's all dark''

--Pink Floyd
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