Re: [Help-bash] Question: Capturing command output (on-screen keyword colorizer/prettifier).

[Chet Ramey]

On 10/4/16 9:20 PM, Matthew Giassa wrote:

> 
>       While I'm able to get the output of echo commands, the PS1/PS2/etc
> variables, and so on, I can't seem to get the output of the "ls" command
> for
> example. I've checked the symbols used to write data out to the console
> via the
> following: readelf --dyn-syms /bin/bash | grep -i -e write -e printf
> 
> Output:
>      6: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (5)
>     13: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (5)
>     39: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (2)
>     98: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (8)
>    142: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (5)
>    152: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (5)
>    191: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (2)
>    192: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (5)
>    213: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND
> address@hidden (5)
> 
>       So as far as I can see, I'm hooking all of the typical commands BASh
> would use to write to the console, yet there is still output which I'm
> not
> capturing.
> 
>       Is there yet another function BASh uses which I would need to hook in
> order to capture all command output within the LD_PRELOAD'ed C library?

Since `ls' is a separate executable, it handles input and output itself.
Bash doesn't get involved with it.

If you want to hook the separate child processes to your LD_PRELOAD
library, you need to make sure that LD_PRELOAD survives the fork and
is available to the loader.  That might be as simple as exporting the
variable.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/