From: Stefan Israelsson Tampe <stefan.ita...@gmail.com>
Subject: Re: capture stdout and stderr
Date: Thu, 24 May 2018 15:25:51 +0200
I think that your code whould work but doesn't because string ports
are not file ports and system commands pipes out to file ports.
'open-input-pipe' uses 'scm_open_process' that returns only a
read-port and a write-port, the write port is then taped the output
string in your run-command.
and it works.
ALso when you create a err-port with pipe, you create a file port
nad this will be used translated as an error port for the system
comand and it all works.
However the failing program uses a string port which is not a file
port and it does not end up capturing the error output in the
system command.
One would wish that guile if the error port is not a file port make
a file port, as done with 'pipe' and create a thread that pipes the
data from the file port to the non file port and your code
would work. Also similarly behavior for read and write ports
towards the shell.
the relevant code is in posix.c, scm_open_process
Hi! Thanks for the message. Indeed, that makes sense. In fact I had
some vague intuition that some magic would be needed to channel the
stderr output into such a string port. I think the manual could be
more explicit about that, though? (e.g. in the section on default
ports
https://www.gnu.org/software/guile/manual/html_node/Default-Ports.html#Default-Ports
). Maybe I should propose a patch to the docs, stating that those
"with-x-to-port" methods only work on file ports.
Thomas
