Re: Faking a TTY on a pipe/socketpair

On 2024-11-18, Eric Pozharski <apple.universe@posteo.net> wrote:

with <20241117093714.675@kylheku.com> Kaz Kylheku wrote:

On 2024-11-16, Muttley@dastardlyhq.com <Muttley@dastardlyhq.com> wrote:

>

So my question is - is there a way to set up a pipe or socketpair**
so that it appears to be a tty from the exec'd programs point of
view, eg ttyname() returns non null?

*SKIP* [ 18 lines   2 levels deep]

The GNU C Library has a mechanism to override this, driven by
environment variables, and a wrapper utility callet "stdbuf" which
uses the environment variables to tell a child process what buffering
discipline to use for stdin, stdour or stderr.

>
Now I understand what's going on (back then I've come to conclusions and
called names (AKA -- I'd been pissed off by 9 out of 12);  I was
wrong).  But variables?  Neither stdbuf(1) nor setbuf(3) give any
directions.  What should I read?

Firstly, I apologize for my bad here, Eric. This is not done in glibc,
but actually by a preloaded shared library called libstdbuf.so. That
comes from CoreUtils.

I'm not sure where/if the environment variables are documented.

To simulate the action of stdbuf in your own program, you need
to LD_PRELOAD libstdbuf, and set the environment variables,
then execute the target program.

See the files src/stdbuf.c and src/libstdbuf.c in the GNU Coreutils
tree.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca